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- oat cell: Any of the small round or oval cells with a high ratio of nuclear protoplasm to cytoplasm that resemble oat grains and are characteristic of small-cell carcinoma.
- oat cell carcinoma: cancer of a highly malignant form that affects the lungs, tends to metastasize to other parts of the body, and is characterized by small round or oval cells resembling oat grains and having a high ratio of nuclear protoplasm to cytoplasm -- called also oat-cell cancer, oat-cell carcinoma, small-cell carcinoma, small-cell lung
- oatcell: Oat cell. Any of the small round or oval cells with a high ratio of nuclear protoplasm to cytoplasm that resemble oat grains and are characteristic of small-cell carcinoma.
- occipital: Of or pertaining to the occiput, or back part of the head, or to the occipital bone, which is the bone forming the rear (and rear bottom) of the skull.
- occipital brain tumor: A tumor in the area of or relating to the occipital lobe. The occipital lobe is the posterior lobe of each cerebral hemisphere that is separated medially from the parietal lobe by the parieto-occipital sulcus, is indistinctly separated more laterally from the temporal and parietal lobes, bears the visual areas, and has the form of a 3-sided pyramid.
- occipital hemmorage: A hemorrhage relating to, or located near the occiput or the occipital bone, a compound bone that forms the posterior part of the skull
- occipital lobe: The posterior lobe of each cerebral hemisphere that bears the visual areas and has the form of a 3-sided pyramid.
- occipital lobe tumor: Se: occipital brain tumor
- occipital tumor: See: occipital, occipital brain tumor, occipital lobe
- ODAC: Oncology drugs advisory committee.
- odema: See edema.
- odontiod: Correct spelling: odontoid. Having the form of a tooth .
- odors: (noun)
1 : a quality of something that affects the sense of smell
2 : a sensation resulting from adequate chemical stimulation of the receptors for the sense of smell
- oedema: See edema.
- olfactory: (adjective)
: of, relating to, or connected with the sense of smell
- olig: See oligodendroglioma.
- oligdenorglial comporoglial: Oligodendroglia. A class of neuroglial (macroglial) cells in the central nervous system. Oligodendroglia may be called interfascicular, perivascular, or perineuronal satellite cells according to their location. The most important recognised function of these cells is the formation of the insulating myelin sheaths of axons in the central nervous system.
- oligo: A combining form meaning a few, a little, too little or too few.
- oligo-astrocytoma: See: oligoastrocytoma
- oligoastrocytoma: Also called a mixed glioma, an astrocytoma with a high proportion of oligodendroglioma cells.
- oligoastrocytoma grade 2: See oligoastrocytoma.
- oligodendraglioma: See: oligodendroglioma
- oligodendro glioma: a tumor of the nervous system composed of oligodendroglia
- oligodendroblastoma: See: oligodendroglioma.
- oligodendroglioma: Oligodendroglioma. May be subdivided into primary brain tumours and the more common, secondary brain tumours. Primary brain tumours (for example astrocytoma, craniopharyngioma, glioma, ependymoma, neuroglioma, oligodendroglioma, glioblastoma multiforme, meningioma, medulloblastoma) arise from the uncontrolled proliferation of cells within the brain. Secondary brain tumours occur from the spread of cancer into the brain from a distant cancerous organ (metastasis).
- oligodendroglioma: A usually slow growing neoplasm derived from and composed of oligodendrogliocytes in varying stages of differentiation.
- oligodendrogliomas: a tumor of the nervous system composed of oligodendroglia
- oligodenglioma: See: oligodendroglioma
- oligonendroblastoma multiforme: See: oligodendroglioma; glioblastoma multiforme
- oligophrenia: subaverage intellectual ability that is equivalent to or less than an IQ of 70, is present from birth or infancy, and is manifested especially by abnormal development, by learning difficulties, and by problems in social adjustment
- mentally retarded adjective
- oliogoodendroglioma: : a tumor of the nervous system composed of oligodendroglia
- olive: (noun)
: an oval eminence on each ventrolateral aspect of the medulla oblongata that contains the inferior olive of the same side --called also olivary body
- ommaya: See Ommaya reservoir
- Oncologist: Oncology is the branch of medicine dealing with tumors (cancer). A medical professional who practices oncology is an oncologist.
- oncology: (noun)
: the study of tumors
- oophorectomy: Removal of an ovary.
- operculum: Operculum refers to the cerebral cortex on the outside surface of the brain.
- optic chasm: See: optic chiasm
- optic chiasim: See: optic chiasm
- optic chiasm: The X-shaped partial decussation on the undersurface of the hypothalamus through which the optic nerves are continuous with the brain -- called also optic chiasma.
Specifically, in the optic chiasm, the nerves connected to the right eye that attend to the right temporal visual field (located in the right retina) remain on the right (ipsilateral) side of the brain, and the nerves from the left eye that attend to the left temporal visual field (located in the left retina) remain on the left (ipsilateral) half of the brain. This allows for parts of both eyes that attend to the right visual field to be processed in the left visual system in the brain, and vice versa.
- optic glioma: A slow-growing glioma of the optic nerve or optic chiasm heralded by visual loss, often with secondary strabismus followed by proptosis and loss of ocular movements. t.
- optic nerve: (noun)
: either of the pair of sensory nerves that comprise the second pair of cranial nerves, arise from the ventral part of the diencephalon, form an optic chiasma before passing to the eye and spreading over the anterior surface of the retina, and conduct visual stimuli to the brain --called also second cranial nerve
- ORBITAL PSEUDOTUMOR: See pseudotumor cerebri.
- osseous: Adjective. Of, relating to, or composed of bone.
- OSSEOUS LESION: Osseous: Having to do with the bone, consisting of bone, or resembling bone
- ossicles: The ossicles (also called auditory ossicles) are the three smallest bones in the human body. They are contained within the middle ear space and serve to transmit sounds from the air to the fluid-filled labyrinth (cochlea).
- ossification: Bone tissue formation
- ossified: See: ossification
- Osteoma: Benign tumour of bone.
- osteomyelitis: (noun)
: an infectious inflammatory disease of bone often of bacterial origin that is marked by local death and separation of tissue
- osteophyte: (noun)
: a pathological bony outgrowth
- otic: (adjective)
: of, relating to, or located in the region of the ear
- p53: p53 is a protein encoded by the TP53 gene. p53 regulates the cell cycle and functions as a tumor suppressor that is involved in preventing cancer. p53 has been described as "the guardian of the genome," "the guardian angel gene," and the "master watchman". If the TP53 gene is damaged, tumor suppression is severely reduced.
- pacchioni granulations: See: pacchionian, arachnoid granulations, pacchionian body, pacchionian depression.
- Pacchioni's granulations: See: Arachnoid granulations
- pacchionian: Any of the small whitish processes that are enlarged villi of the arachnoid membrane of the brain which protrude into the superior sagittal sinus and into depressions in the neighboring bone -- called also arachnoid villus, pacchionian body.
- pacchionian body: Pacchioni described granulations over the meninges in 1721. Those structures, namely arachnoid vili, are the main site of absorption of the cerebrospinal fluid into venous blood of the dural venous sinuses. The arachnoid villi are more abundant in the superior sagittal sinus and consist of an extension of the subarachnoid space into the dura mater. The separation between the subarachnoid space and the venous blood is made by a thin cellular layer, derived from the epithelium of the arachnoid and the endothelium of the sinus. The arachnoid villi are not covered by the dura mater. In the adult and the old people the villi become bigger and are called pacchionian bodies or arachnoid granulations. Frequently they become calcified and leave impressions in the calvaria.
- pacchionian depressions: Impressions in the calvaria left by calcified pacchionian bodies or arachnoid granulations. See pacchionian body.
- pacchionian granulation: See pacchionian body.
- pacchionian granulations: See: pacchionian body, pacchionian, arachnoid granulations, pacchionian depressions
- pacchionion: See arachnoid granulations.
- pacchionion granulation: See: pacchionian body
- paccionian depression: See: pacchionian body.
- pacemaker: (noun)
1 : a body part (as the sinoatrial node of the heart) that serves to establish and maintain a rhythmic activity
2 : an electrical device for stimulating or steadying the heartbeat or reestablishing the rhythm of an arrested heart --called also pacer
- pachioni granulation: See arachnoid granulations
- paclitaxel: An alkaloid drug that is an extract from the Pacific yew, Taxus brevifolia. It inhibits microtubule disassembly and is used as a chemotherapy agent to treat bladder, oesophageal and lung cancers and is being investigated as a treatment for leukaemia and lymphoma.
- palsey of the seventh nerve: See Bell's palsey.
- palsy: Palsy is the paralysis of a body part, often accompanied by loss of sensation and by uncontrolled body movements, such as shaking. Medical conditions involving palsy include cerebral palsy, brachial palsy, and Bell's palsy.
- pancoast: Pancoast Tumor. A malignant tumor formed at the upper extremity of the lung.
- pancoast tumor: Tumor originating from the superior sulcus of the lung that invades all or a portion of the brachial plexus.
- pancytopenia: Pancytopenia is a medical condition in which there is a reduction in the number of red and white blood cells, as well as platelets.
Pancytopenia is generally due to diseases affecting the bone marrow, although peripheral destruction of all lines of blood cells in hypersplenism (overactive spleen) is a recognised cause. Bone marrow problems causing pancytopenia include myelofibrosis, leukemia, aplastic anemia, and the malignant form of osteoporosis.
Pancytopenia can also be caused by familial hemophagocytic syndrome, which is a type of immunodeficiency syndrome. The disease is marked by an inappropriate and ineffective T cell activation that leads to an increased hemophagocytic activity. The T cell activated macrophages engulf erythrocytes, leukocytes, platelets, as well as their progenitor cells. Such finding is common in the syndrome, which is also referred to as hemophagocytic lymphohistiocytosis (HLH). Along with pancytopenia, HLH is characterized by fever, splenomegaly, and hemophagocytosis in bone marrow, liver, or lymph nodes.
Iatrogenic causes of pancytopenia include chemotherapy for malignancies if the drug or drugs used cause bone marrow suppression. Rarely, drugs (antibiotics, blood pressure medication, heart medication) can cause pancytopenia. The antibiotic Linezolid can cause pancytopenia in some individuals. Pancytopenia usually requires a bone marrow biopsy in order to distinguish among different causes.
- papilledema: Edema (swelling) of the optic disk (papilla), most commonly due to increased intracranial pressure, malignant hypertension or thrombosis of the central retinal vein.
- papilloma: Papilloma. Benign tumour of epithelium.
Warts (caused by papilloma virus) are the most familiar example and each is a clone derived from a single infected cell.
The epithelim is the covering of internal and external surfaces of the body, including the lining of vessels and other small cavities. It consists of cells joined by small amounts of cementing substances. Epithelium is classified into types on the basis of the number of layers deep and the shape of the superficial cells.
- para-falcine: See: Parafalcine
- paraclinoid: A region of the brain defined as a pyramid-formed space formed by the dural covering of the anterior clinoid process. The superior border is formed by the continuity of the anterior petroclinoid fold, anteriorly on the superior surface of the anterior clinoid process and medially in the direction of the diaphragma sellae. This dural sheet encircles the internal carotid artery and forms the so-called distal dural ring of the internal carotid artery. The medial border of the paraclinoid region is formed by the body of the sphenoid bone and the adjacent periosteal sheet. The inferior border is formed by a fibrous plate between the middle and anterior clinoid processes. This so-called proximal dural ring separates the venous compartments of the cavernous area from the paraclinoid area. The lateral border is formed by the lateral surface of the anterior clinoid process with its dural covering. The arterial supply of this region is provided by branches of the intracavernous carotid segment and the ophthalmic artery. The important nerves in close vicinity to the paraclinoidal area are the optic and the oculomotor nerves. Understanding and knowledge of the topographic anatomy of the paraclinoid area is essential for microsurgical exposure of this region.
- paraclinoid region: See paraclinoid
- Parafaicine meningioma: See: parafalcine, meningioma
- parafalacine: See: parafalcine
- parafalcine: Falcine refers to the falx cerebri, a tissue division between the right and left hemispheres. Parafalcine would mean next to the falx.
- parafalcine area: See: parafalcine
- parafalcine calcification: See: parafalcine; calcification
- parafalcine lesion: See: parafalcine, lesion
- parafalcine mass: See parafalcine.
- parafalcine meningima: See: parafalcine, meningioma
- parafalcine meningioma: See: parafalcine, meningioma
- parafalcine meningioma: See: parafalcine; meningioma.
- parafalcine meningiomas: See: parafalcine, meningioma
- parafalcine meningoma: See: parafalcine, meningioma
- parafalcine region: See parafalcine
- paraganglioma: A paraganglioma is a rare neuroendocrine neoplasm that may develop at various body sites (including the head, neck, thorax and abdomen). About 97% are benign and cured by surgical removal; the remaining 3% are malignant because they are able to produce distant metastases. Paragangliomas are still sometimes referred to using older, obsolete terminology (for example as "chemodectomas" or "glomus tumors", the latter not to be confused with glomus tumors of the skin).
- paragangliomas penial region brain: See paraganglioma and pineal region.
- paraital occipital: See: parietal lobes, occipital lobe
- paralysis: Complete or partial loss of function especially when involving the power of motion or of sensation in any part of the body.
- paramesencephalic: Closely related to the midbrain, also known as the mesencephalon.
- paranasal: Adjacent to the nasal cavities; especially : of, relating to, or affecting the paranasal sinuses, being any of various sinuses (as the maxillary sinus and frontal sinus) in the bones of the face and head that are lined with mucous membrane derived from and continuous with the lining of the nasal cavity.
- paraneoplastic: (adjective)
: caused by or resulting from the presence of cancer in the body but not the physical presence of cancerous tissue in the part or organ affected
- paraneoplastic syndrome: A collection of symptoms or clinical signs that are found in patients that have malignant disease. By definition, the signs and symptoms are not produced by a direct effect of a tumour or its metastasis nor due to direct invasion, compression, metastasis, infection, nutritional deficiency or treatment of the underlying neoplasm. Paraneoplastic syndromes can arise from tumour produced biologically active polypeptides or proteins, autoimmunity or immune complex production and immune suppression, blockade of the normal effect of a hormone, the release of substances from tumor associated endothelium which are not normally released and finally unknown causes. The best characterised paraneoplastic syndrome is the syndrome of inappropriate ADH.
- parasagital: See: parasagittal
- parasagittal: Situated alongside of or adjacent to the sagittal plane, the deeply serrated area between the two parietal bones in the top of the skull.
- parenchyma: The essential elements of an organ, used as a general term to designate the functional elements of an organ, as distinguished from its framework or stroma.
- parenchymal: The tissue characteristic of an organ, as distinguished from associated connective or supporting tissues. Parenchyma comprises the essential or functional parts of an organ.
- paresthesias: A paresthesia is a sensation of tingling, pricking, or numbness of the skin with no apparent long-term physical effect. It is commonly referred to as the feeling of "pins and needles" or of a limb "falling asleep". These feelings may be episodic or chronic. Episodic paresthesias of the hands and feet are sometimes associated with hyperventilation and panic attacks, or can result when sustained pressure has been applied over a nerve, inhibiting or stimulating its function. Removing the pressure will typically make the sensation subside. Chronic paresthesia indicates a problem with the functioning of neurons. It can be associated with peripheral vascular disease, vitamin deficiency, malnutrition, diabetes, hypothyroidism, hypoparathyroidism, rheumatoid arthristis, carpal tunnel syndrome, neck and spine problems, and a wide variety of other conditions.
- parfalcine meningioma: See: parafalcine, meningioma
- parietal: (noun)
: a parietal part (as a bone)
- parietal lobe: (noun)
: the middle division of each cerebral hemisphere that is situated behind the central sulcus, above the fissure of Sylvius, and in front of the parieto-occipital sulcus and that contains an area concerned with bodily sensations.
- parietal lobes: The parietal lobes are found starting above the ear and spanning about three or four inches towards the back of the head on each side of the head. The parietal lobes can be divided into two functional regions. One involves sensation and perception and the other is concerned with integrating sensory input, primarily with the visual system. Individuals with damage to the left parietal lobe can result in right-left confusion, difficulty with writing (agraphia) and difficulty with mathematics (acalculia).
- parietal parafalcine meningioma: See: parietal lobe, parietal lobes, parafalcine, meningioma
- parietal plemorphic xanthoastrocytoma: See: pleomorphic xanthoastrocytoma
- Parinaud's syndrome : Parinaud's Syndrome, also known as dorsal midbrain syndrome is a group of abnormalities of eye movement and pupil dysfunction. It is caused by lesions of the upper brain stem. Parinaud's Syndrome results from injury, either direct or compressive, to the dorsal midbrain. Brain tumors in the pineal gland or midbrain are the most common lesion producing this syndrome, primarily in young patients.
- Parkinson's disease: A disorder in which the patient suffers from tremors, stiffness, and slowness of movement.
- parkinsonism: : PARKINSON'S DISEASE
2 : any of several neurological conditions that resemble Parkinson's disease and that result from a deficiency or blockage of dopamine caused by degenerative disease, drugs, or toxins
- parlodel: Antiparkinsonian agent, lactation prevention, acromegaly therapy.
- partial complex seizures: See: Seizure
- partial lobe: See: parietal lobe
- partially calcified aneurysm: See: calcification, aneurysm
- partially calcified cerebral mass: See: calcification
- partially calcified mass: See: calcification
- partially calcified meningioma: See: calcification, meningioma
- partially calcified meningioma in anterior: See: calcification; meningioma
- partially calcified right cerebellar mass: See: calcification
- pathologist: A person that specializes in the branch of medicine which treats the essential nature of the disease, especially the structural and functional changes in tissues and organs of the body which are caused by disease. The structural and functional manifestations of disease.
- Patrin-2: An experimental, orally administered substance being tested for its potential to widen the therapeutic window and to make additional tumour types susceptible to existing therapies. Thought to be effective to potentiate the activity of O6-alkylating agents including dacarbazine (DTIC), carmustine (BCNU), Muphoran and Temozolomide (Temodal).
- PCV: Procarbazine, CCNU and vincristine chemotherapy protocol. Click here for more information.
- Peacock boost: A radiation treatment which uses a device called the Peacock System, a multileaf intensity modulating collimator that can be attached to a standard linear accelerator, Linac. As the delivery head of the Linac rotates around the patient, the Peacock attachment is able to divide the Linac's radiation beam into thousands of very thin beamlets which are cross-fired at varying intensities so that they conform to the tumor's exact shape, size and location. It's called Peacock because of the manner in which the radiation fans out, like the tail of the peacock. Radiation can be delivered single dose or fractionated into 20 to 30 sessions.
- pediatric: (adjective)
: of or relating to pediatrics
- peduncle: Pedunculated. Having a peduncle; growing on a peduncle; as, a pedunculate flower; a pedunculate eye, as in a lobster.
- pedunculated: Having a peduncle; growing on a peduncle; as, a pedunculate flower; a pedunculate eye, as in a lobster.
- pellucidum: See septum pellucidum.
- penicillamine: Penicillamine. Product of acid hydrolysis of penicillin that chelates heavy metals (lead, copper, mercury) and assists in their excretion in cases of poisoning. Also used in treatment of rheumatoid arthritis although its mode of action as an antirheumatic drug is not clear.
- pericarditis: Inflammation of the lining around the heart (the pericardium) causing chest pain and accumulation of fluid around the heart (pericardial effusion).
- pericytes: A cell of the connective tissue about capillaries or other small blood vessels.
- perifalcine: See: parafalcine
- peripheral: Adjective. a) of, relating to, involving, forming, or located near a periphery or surface part (as of the body); b) of, relating to, affecting, or being part of the peripheral nervous system ; c) of, relating to, or being the outer part of the field of vision ; d) of, relating to, or being blood in the systemic circulation .
- peripheral neuropathy: A functional disturbance or change in the peripheral (situated away from a center or central structure) nervous system.
- perivascular: relating to, occurring in, or being the tissues surrounding a blood vessel
- periventricular: situated or occurring around a ventricle especially of the brain
- PET scan: Positron Emission Tomography (PET), a medical imaging system in which a radiopharmaceutical attaches to specific kinds of tissues, emitting a positron during decay and annihilating within a short distance (generally less than 1 mm) to create two photons which can be externally detected. In this case, the radiation source is located within the patient, as opposed to external to the patient as in most other modalities.
- petrous apex: (noun)
: a division of the bony labyrinth of the inner ear coiled into the form of a snail shell and consisting of a spiral canal in the petrous part of the temporal bone in which lies a smaller membranous spiral passage that communicates with the saccule at the base of the spiral, ends blindly near its apex, and contains the organ of Corti
- petrous bone : Of, relating to, or constituting the exceptionally hard and dense portion of the human temporal bone that contains the internal auditory (hearing) organs and is a pyramidal process wedged in at the base of the skull between the sphenoid and occipital bones with its lower half exposed on the surface of the skull and pierced by the external auditory meatus (the canal leading from the opening of the external ear to the eardrum).
- phagocytic: Having the ability to engulf by phagocytosis (uptake of material into a cell) : capable of functioning as phagocytes
- phase: Relative to clinical trials:
Phase 1: researchers test an experimental drug or treatment in a small group of people (20-80) for the first time to evaluate its safety, determine a safe dosage range, and identify side effects.
Phase 2: the experimental study drug or treatment is given to a larger group of people (100-300) to see if it is effective and to further evaluate its safety.
Phase 3: the experimental study drug or treatment is given to large groups of people (1,000-3,000) to confirm its effectiveness, monitor side effects, compare it to commonly used treatments, and collect information that will allow the experimental drug or treatment to be used safely.
Phase 4:post marketing studies delineate additional information including the drug's risks, benefits, and optimal use.
- phenylketonuria: A metabolic disorder that is caused by an enzyme deficiency resulting in the accumulation of phenylalanine and its metabolites in the blood and their subsequent excretion in the urine. It is an inherited trait and usually causes severe mental retardation, seizures, eczema, and abnormal body odor unless phenylalanine is restricted from the diet beginning at birth. Abbreviation PKU ; called also phenylpyruvic amentia, phenylpyruvic oligophrenia.
- phenytoin: Phenytoin. A medication commonly used to treat seizure disorders and epilepsy.
- phesodu cererbral eye tumor: See: pseudotumor cerebri
- phlebotomy: (noun)
: the letting of blood for transfusion, pheresis, diagnostic testing, or experimental procedures and esp. formerly for the treatment of disease --called also venesection, venotomy
- phosphatidylcholine: any of several waxy hygroscopic phospholipids in which phosphatidic acid has formed an ester with choline and which are widely distributed in animals and plants, form colloidal solutions in water, and have emulsifying, wetting, and antioxidant properties ; also : a mixture of or a substance rich in lecithins -- called also phosphatidylcholine
- phosphatidylserine: A derivative of phosphatidic acid in which the phosphoric acid is bound in ester linkage to a serine moiety. Complete hydrolysis yields 1 mole of glycerol, phosphoric acid and serine and 2 moles of fatty acids.
- photo: or photo-
: light : radiant energy
- pia: The pia mater is the delicate innermost layer of the meninges, the membranes surrounding the brain and spinal cord.
The thin, mesh-like pia mater closely envelops the entire surface of the brain, running down into the fissures of the cortex. It supplies blood to the superficial areas of the cortex and supports larger blood vessels passing over the surface of the brain. The pia mater is anchored to the brain by the processes of astrocytes.
- pia mater: (noun)
: the delicate and highly vascular membrane of connective tissue investing the brain and spinal cord, lying internal to the arachnoid and dura mater, dipping down between the convolutions of the brain, and sending an ingrowth into the anterior fissure of the spinal cord --called also pia
- pienal gland: See: Pineal gland
- pilocydic astrocytoma: See: pilocytic astrocytoma
- pilocytic : See pilocytic astrocytoma
- pilocytic astrocytoma: Pilocytic astrocytomas occur mainly in children. They are the most benign of the astrocytomas. These are usually non-infiltrating tumors which occasionally form cysts or are enclosed in a cyst. Invasion or spread to other parts of the brain and spinal cord is rare. Although they are slow growing, these tumors can become very large. Many optic gliomas and cerebellar astrocytomas are pilocytic astrocytomas. Brain stem gliomas, hemispheric and diencephalic gliomas can also be grade I tumors.
- piloerection: involuntary erection or bristling of hairs due to a sympathetic reflex usually triggered by cold, shock, or fright or due to a sympathomimetic agent
- pin: A long slender metal rod for the fixation of the ends of fractured bones.
- pinael cytoma: See: pineal tumor; pinealcytoma; pineal gland.
- pineal: Shaped like a pine cone. Pertaining to the pineal body.
- pineal blastoma: See pineoblastoma.
- pineal body: See pineal gland.
- pineal cyst: A cyst of the pineal gland (a small, unpaired flattened body shaped somewhat like a pine cone below the splenium of the corpus callosum).
- pineal cysts: Pineal. A gland-like structure in the brain which appears to be the major site of melatonin biosynthesis. The exact role of the pineal remain obscure.
Cyst. Any closed cavity or sac that is lined by epithelium often contains liquid or semi-solid material.
- pineal cytoma: See pineal tumor.
- pineal gland: (noun)
: a small body that arises from the roof of the third ventricle and is enclosed by the pia mater and that functions primarily as an endocrine organ -- called also pineal, pineal body, pineal organ
- pineal region: The pineal gland is found at the back of the third ventricle of the brain. Ventricles are fluid-filled spaces within the brain. The functions of the pineal gland are not fully understood, but one function is to produce the hormone melatonin. Melatonin is involved in regulating the body’s 'internal clock', controlling when we sleep and when we wake.
Pineal region tumors can be made up of different types of cells. The most common type of tumor in the pineal region is known as a germinoma. Germinomas develop from germ cells (cells in a very early stage of development). They are fast-growing and may often spread to other parts of the brain. Other types of pineal tumour include: astrocytomas, teratomas, meningiomas, pineocytomas, and pineoblastomas.
Symptoms of tumours in the pineal region are usually due to increased pressure within the skull. This may be due to a blockage in the ventricles (fluid-filled spaces) of the brain, which leads to a build-up of cerebrospinal fluid (CSF). CSF is the fluid that surrounds and protects the brain and spinal cord. This increased pressure may also be caused by swelling from the tumor itself.
The first sign of this type of tumour in children is often hydrocephalus (water on the brain), which can cause enlargement of the skull.
Other symptoms may be headaches, vomiting, and eyesight problems. Children are often tired and irritable. The tumor may cause difficulty in looking upwards, or focusing on close objects.
Symptoms may be caused by the tumor pressing on surrounding areas of the brain, such as the cerebellum. This will lead to problems with coordination and balance. People often have difficulty walking and may appear to stumble or walk awkwardly.
Tumors in the pineal region may extend to the pituitary gland and cause delayed puberty in teenagers, or other hormonal difficulties.
- pineal tumor: These tumors arise in the region of the pineal gland, a small structure deep within the brain. The three most common types of pineal region tumors are gliomas, germ cell tumors and pineal cell tumors.
- pinealblastoma: See: See pineoblastoma
- pinealcytoma: Pineocytoma, also known as a pinealocytoma, is a benign, slowly-growing tumor of the pineal gland.
- pinealoma: An uncommon tumor of the pineal body composed of neoplastic nests of large epithelial cells. Symptoms include hydrocephalus, conjugate paralysis of upward gaze, disturbances of gait, and precocious puberty, the last possibly due to the suppression of pineal secretion of melatonin.
- pineoblastoma: A type of neuroepithelial tumor that is a pinealoma in which the pineal cells are not well differentiated.
- pineoblastomas: See: pineoblastoma.
- pineocytoma: Pineocytoma, also known as a pinealocytoma, is a rare benign, slowly-growing tumor of the pineal gland. Unlike the similar condition, pineal gland cyst, it is uncommon.
- pituatary tumor: Pituitary tumor. A tumor of the endocrine gland located at the base of the brain, in the small recess of a bone - certain sections of the pituitary each secrete important hormones including growth hormone (GH) and antidiuretic hormone (ADH).
- pituitary : 1 : of or relating to the pituitary gland
2 : caused or characterized by secretory disturbances of the pituitary gland
- pituitary adenoma: A benign neoplasm of the anterior pituitary gland.
- pituitary apoplexy: Sudden hemorrhage into or ischemic necrosis of a normal or adenomatous pituitary gland.
- pituitary fossa: See sella turcica and fossa.
- pituitary gland: A small, oval endocrine gland attached by a stalk to the base of the brain and consisting of an anterior and a posterior lobe. It secretes hormones influencing body growth, metabolism, the activity of other endocrine glands, etc.
- pituitary infundibulum: Also known as Pituitary stalk, is the connection between the hypothalamus and the pituitary.
- pituitary macroadenoma: A pituitary tumor greater than 1 cm in maximal diameter (vide infra). Macroadenomas have broken out of the confines of the pituitary gland, and almost always have microscopic invasion of the dura lining the sella turcica. Probability of total cure by resection alone plummets when you have a macroadenoma.
- pituitary microadenoma: A pituitary tumor less than 1 cm in maximal diameter (vide infra). Microadenomas typically have a higher chance of being resected totally, because they may be totally contained within the pituitary gland itself.
- pituitary tumor: A tumor of the pituitary gland (an endocrine gland suspended beneath the brain in the pituitary fossa of the sphenoid bone, suppling numerous hormones that govern many vital processes).
- piturity: See: pituitary; pituitary gland.
- pitutury adenoma: A pituitary tumor.
- plaque: A histopathologic (the tissue changes that affect a part or accompany a disease) lesion of brain tissue that is characteristic of Alzheimer's disease and consists of a cluster of degenerating nerve endings and dendrites around a core of amyloid -- called also senile plaque.
- plasmacytoma: Malignant tumour of plasma cells, very similar to a myeloma (plasmacytomas usually develop into multiple myeloma).
- plastic: (adjective)
1 : capable of being deformed continuously and permanently in any direction without breaking or tearing
2 : capable of growth, repair, or differentiation
3 : of, relating to, or involving plastic surgery <' repair>
- platelets: see blood platelets
- platinum: A metal that is an important component of some anticancer drugs, such as cisplatin and carboplatin.
- plemorphic: Correct spelling is pleomorphic. Having the ablility to assume different forms. Also called pleiomorphic.
- pleocytosis: An abnormal increase in the number of cells (as lymphocytes) in the cerebrospinal fluid
- pleomorphic xanthoastrocytoma: A pleomorphic xanthoastrocytomas is a rare tumor thought to arise from a type of cell of the central nervous system known as a glial cell. These tumors likely originate from a specific type of glial cell known as an astrocyte. Astrocytes make up the supportive network of the brain. These cells are named for their star-like appearance.
Pleomorphic xanthoastrocytomas generally arise superficially from the cerebral hemispheres (upper most sections) of the brain and the leptomeninges (coating of the brain). Rarely do these tumors arise from the spinal column. Pleomorphic xanthoastrocytomas affect males and females equally; the average age at diagnosis is 12 years. Very rarely, these tumors undergo transformation to a more malignant tumor.
- pleomorphism: The assumption of various distinct forms by a single organism or species; also the property of crystallizing in two or more forms.
- plexiform: Resembling a plexus or network.
- plexus: A general term for a network of lymphatic vessesl, nerves or veins.
- PNET: Primitive neuroectodermal tumor, a type of brain tumor that recent research suggests develops from primitive (developing) nerve cells that normally do not remain in the body after birth. Primitive neuroectodermal tumors are often called medulloblastomas.
- PNET Medulloblastoma: See: PNET and Medulloblastoma
- poly ICLC: Polyinosinic-polycytidylic acid stabilized with polylysine and carboxymethylcellulose. An experimental chemotherapeutic agent used to treat malignant gliomas.
- POLY-ICLC: See: poly ICLC.
- polycytoma: A many-celled tumor.
- polylysine: (noun)
: a protein whose polypeptide chain consists entirely of lysine residues
- polymorphism: The quality or state of being able to assume different forms: as a) existence of a species in several forms independent of the variations of sex; or b) the property of crystallizing in two or more forms with distinct structure.
- pons: The pons is a structure located on the brain stem. The pons contains nuclei that relay signals from the cerebrum to the cerebellum, along with nuclei that deal primarily with sleep, respiration, swallowing, bladder control, hearing, equilibrium, taste, eye movement, facial expressions, facial sensation, and posture.
- pons calcifications: See: calcification
- pontine: Pertaining to the pons.
- pontine glioma: See pontine and glioma.
- pontine hemmorhage: A hemmorhage in the area of the brain known as the pons.
- porencephalic: Relating to or characterized by porencephaly, which is the presence of cavities in the brain.
- porencephalic cyst: A gap in the brain where there should be healthy brain tissue.
- porencephalic cyst in middle of brain: See porencephalic cyst.
- porencephalic cyst in the thalamus: This is an extremely rare disorder of the central nervous system involving a cyst or cavity in a cerebral hemisphere. The cysts or cavities are usually the remnants of destructive lesions, but are sometimes the result of abnormal development. The disorder can occur before or after birth.
- porencephaly: The presence of cavities in the brain.
- PORTACAVAL SHUNT: A surgical shunt, or passage way, by which the portal vein is made to empty into the inferior vena cava in order to bypass a damaged liver.
- posterior: Adjective--Situated behind.
- posteriorly: See: posterior
- PPAR: Peroxisome Proliferator-Activated Receptors. In the field of molecular biology, the PPARs are a group of nuclear receptor proteins that function as transcription factors regulating the expression of genes. PPARs play essential roles in the regulation of cellular differentiation, development, and metabolism (carbohydrate, lipid, protein), and tumorigenesis.
- precocious puberty: A condition in which a child shows physical signs of sexual maturity at an abnormally early age--below 8 in girls and 9 in boys. Precocious puberty is about 10 times more common in girls than in boys, and it can have many different causes, including: a problem in the brain, especially a brain tumor or a brain injury (trauma), a gland problem that causes abnormal hormone levels, especially very low levels of thyroid hormones or high levels of adrenal hormones, tumors of the ovaries, testicles, liver or another organ. Cells in these tumors manufacture either the true sex hormones, or chemicals that act like the sex hormones, and these trigger the abnormally early sexual growth. See hypothalamic hamartoma.
- precursor cell: A precursor cell, also called a blast cell or simply blast, is a type of partially differentiated, usually unipotent (one that has the capacity to develop into only one type of tissue/cell type) cell that has lost most or all of the stem cell multipotency.
A blastoma is a type of cancer created by malignancies of precursor cells.
- prefrontal lobe: the anterior part of the frontal lobe that is made up chiefly of association areas, mediates various inhibitory controls, and is bounded posteriorly by the ascending frontal convolution
- premotor cortex: The premotor cortex portion of the brain controls the coordination of series of movements or intricate, complex movements.
- primary: (adjective)
1 a (1) : first in order of time or development
(2) : relating to or being the deciduous teeth and esp. the 20 deciduous teeth in the human set
b : arising spontaneously : IDIOPATHIC <' tumors>
2 : belonging to the first group or order in successive divisions, combinations, or ramifications <' nerves>
3 : of, relating to, or being the amino acid sequence in proteins -- compare SECONDARY 3, TERTIARY 2
- primary epidermoid : See cholesteatoma.
- primary tumor: Primary tumor. The original tumor of a cancer diagnosis. Cancer cells can invade and damage nearby tissues and organs. Also, cancer cells can break away from a malignant tumor and enter the bloodstream or the lymphatic system. This is how cancer spreads from the original (primary) tumor to form new tumors in other parts of the body
- primitive neuroectodermal tumor: This tumor type occurs most often in the cerebrum. Also called PNET. The term is used by some to identify the pineoblastoma, polar spongioblastoma, medulloblastoma and medulloepithelioma, all of which are very rare tumors, except for the medulloblastoma.
- Procarbazine: An anticancer drug (antineoplastic) used most commonly in the combination chemotherapy known as PCV. Sometimes used by itself. There are some restrictions on the foods you can eat while taking this drug. We will post more details in the noteworthy treatments section of this site soon.
- prodromes: A premonitory symptom, or symptom giving warning, of disease -- called also prodroma.
- proencephalic: This appears to be a misspelling of porencephalic.
- prognosis: The prospect of recovery as anticipated from the usual course of disease or peculiarities of the case.
- progression free survival: The survival time in which a disease has stabilized and not advanced to a worse condition. For example, the time in which a tumor has not grown any larger.
- progressive supranuclear palsy : An uncommon neurological disorder that is of unknown etiology, that typically occurs from late middle age onward, and that is marked by loss of voluntary vertical eye movement, muscular rigidity and dystonia of the neck and trunk, pseudobulbar paralysis, bradykinesia, and dementia -- called also supranuclear palsy.
- prolactin: A substance produced from the anterior pituitary gland, it's found in normal females and males. Prolactin's principal physiological action is to initiate and sustain lactation.
- prolactin level: Prolactin. Pituitary lactogenic hormone (23 kD) Synthesised on endoplasmic reticulum bound ribosomes as preprolactin that has an N terminal signal peptide that is cleaved from the mature form. The conversion of preprolactin to prolactin has been much used as an assay for membrane insertion.
- prolactinoma: A pituitary adenoma that secretes excessive amounts of prolactin.
- proliferation: (noun)
1 a : rapid and repeated production of new parts or of offspring (as in a mass of cells by a rapid succession of cell divisions)
b : a growth so formed
2 : the action, process, or result of increasing by proliferation
- prophylaxis: A measure taken to maintain health and prevent the spread of disease.
- proptosis: forward projection or displacement especially of the eyeball
- protease: Protease: An enzyme that can split a protein into peptides (from whence the protein was originally created)
- protrusion: the quality or state of protruding
2 : something (as an anatomical part) that protrudes
- ps: Function: abbreviation
- psedotumor cerebrii: See: pseudotumor cerebri
- pseudo: (combining form)
: false : spurious
- Pseudo - tumor cerebri: an abnormal condition that is characterized by increased intracranial pressure, headaches of varying intensity, and papilledema without any demonstrable intracranial lesion and that tends to occur in overweight women from 20 to 50 years of age -- called also benign intracranial hypertension
- pseudo aneurysm: a vascular abnormality (as an elongation or buckling of the aorta) that resembles an aneurysm in radiography
- pseudo brain tumor: See pseudotumor cerebri.
- pseudo bulbar palsy: Simulating that (as bulbar paralysis) which is caused by lesions of the medulla oblongata.
- pseudo cerebral brain tumor: See pseudotumor cerebri
- pseudo cerebral eye tumor: See pseudotumor cerebri.
- pseudo cerebral hypertension: See pseudotumor cerebri.
- pseudo cerebral tumor: See pseudotumor cerebri.
- pseudo cerebri tumor: See: pseudotumor cerebri.
- pseudo medulla tumor: See pseudotumor cerebri.
- pseudo tumor: an abnormality (as a temporary swelling) that resembles a tumor
- pseudo tumor cerebri: See pseudotumor cerebri.
- pseudo tumor in the spine: See: pseudotumor cerebri
- pseudo tumour cerebri: See pseudotumor cerebri.
- pseudocerebri tumor: See: pseudotumor cerebri
- pseudomonas exotoin : A bacterial toxin which has been modified by addition of interleukin 4 (IL-4). This toxin has been designated scientifically as IL-4 (38-37)PE38KDEL, and is extremely deadly for malignant glioblastoma cells. but not for normal, healthy cells.
- pseudoprogression: pseudoprogression is defined as an increase of contrast-enhancement and/or edema on MRI without true tumour progression. Mimics tumor growth but is caused by treatment.
- pseudotumor: An enlargement that resembles a tumor. It may result from inflammation, accumulation of fluid or other causes, and may or may not regress spontaneously.
- pseudotumor cebri: See: pseudotumor cerebri
- pseudotumor celebir: See: pseudotumor cerebri
- pseudotumor celebri: See: pseudotumor cerebri
- pseudotumor cerbri: See: pseudotumor cerebri
- pseudotumor cerebri: A condition caused by cerebral swelling and associated with a number of pathologic conditions, marked by raised intracranial pressure with normal CSF fluid, headache, nausea, vomiting and swelling of the optic disc but without neurological signs.
- pseudotumor cerebri, pituitary tumor and papille: See pseudotumor cerebri.
- pseudotumor cerebri.: See: pseudotumor cerebri
- pseudotumor cerebril: See pseudotumor cerebri.
- pseudotumorcerebri: See pseudotumor cerebri.
- pseudotumors: See pseudotumor cerebri.
- pseudovulvar syndromes: Simulating that (as bulbar paralysis) which is caused by lesions of the medulla oblongata
- psudo occipital brain tumor: See pseudotumor cerebri.
- psuedo brain tumor: See psuedotumor cerebri.
- psuedo cranial tumor: See: pseudotumor cerebri.
- psuedo lymphoma: See pseudotumor. See lymphoma.
- psuedo occipital tumor syndrome: See: pseudotumor cerebri
- psuedo tumor: See pseudotumor cerebri.
- psuedo tumor cerebelli: See pseudotumor cerebri.
- psuedo tumor cerebri: intracranial pressure, headaches of varying intensity, and papilledema without any demonstrable intracranial lesion and that tends to occur in overweight women from 20 to 50 years of age -- called also benign intracranial hypertension
- psuedo tumor cerebri hypothalomus: See pseudotumor cerebri.
- psuedo tumors: Pseudotumour. An enlargement that resembles a tumour.
- psuedotumor: See: pseudotumor cerebri
- psychomotor: 1. Of or relating to motor action directly proceeding from mental activity; or 2. of or relating to temporal lobe epilepsy, as in 'psy·cho·mo·tor seizures.'
- psychosis: a serious mental disorder (as schizophrenia) characterized by defective or lost contact with reality often with hallucinations or delusions
- ptc: A crystalline compound that is extremely bitter or tasteless depending on the presence or absence of a single dominant gene in the taster -- called also phenylthiourea.
- PTEN: Phosphatase and tensin homolog (PTEN) is a protein that is encoded by the PTEN gene. Mutations of this gene are a step in the development of many cancers.
PTEN acts as a tumor suppressor gene.
- pterional: Pteron. The region of the skull, in the temporal fossa back of the orbit, where the great wing of the sphenoid, the temporal, the parietal, and the frontal hones approach each other.
- pterygoid muscle: Either of two muscles extending from the sphenoid bone to the lower jaw.
- ptosis: (noun)
: a sagging or prolapse of an organ or part; esp : a drooping of the upper eyelid (as from paralysis of the oculomotor nerve)
- pulmonary: Pertaining to the lungs.
- pulmonary artery: (noun)
: an arterial trunk or either of its two main branches that carry blood to the lungs:
a : a large arterial trunk that arises from the conus arteriosus of the right ventricle and branches into the right and left pulmonary arteries --called also pulmonary trunk
b : a branch of the pulmonary trunk that passes to the right lung where it divides into branches --called also right pulmonary artery
c : a branch of the pulmonary trunk that passes to the left lung where it divides into branches --called also left pulmonary artery
- punctate: an abnormality (as a temporary swelling) that resembles a tumor
- pupil dialation: The pupil of the eye is the black center of the iris. The iris is the structure that gives the eye it's color. The pupil is actually the opening in the center of the iris that allows light to enter the eye. Neurological input to the iris muscles controls the pupil diameter; in bright light the pupil constricts, in dim light the pupil widens. Mydriatics are pharmaceutical drops which act upon the muscles of the iris to enlarge the pupil diameter. Optometric physicians use mydriatic drops for pupil dilation in order to visualize the anatomic structures behind the iris in the back of the eye.
- pure germinoma: A germinoma is a type of germ cell tumor which is not differentiated upon examination. It may be benign or malignant. The term germinoma most often has referred to a tumor in the brain that has a histology identical to two other tumors: dysgerminoma in the ovary and seminoma in the testis.
- rabdoid: Of or pertaining to the sagittal suture; in the region of the sagittal suture; rabdoidal; as, the sagittal furrow, or groove, on the inner surface of the roof of the skull.
- rabdoid meningioma: A meningioma located in the region of the sagittal suture; rabdoidal; as, the sagittal furrow, or groove, on the inner surface of the roof of the skull.
- rad: Rad: Radiation absorbed dose, a measure for a dose of ionizing radiation.
- radiation: Energy radiated in the form of waves or particles. See also, radiation therapy.
- radiation necrosis: Death of tissue caused by radiation.
- radiation sensitizers: Chemotherapeutic agents that are highly responsive to ionizing radiation and enhance the effectiveness of radiation treatment are termed radiation sensitizers. Radiation sensitizers act in a number of ways to make cancer cells more susceptible to death by radiation than surrounding normal cells.
- radiation surgery: A radiation therapy technique that delivers a single high dose of radiation directly to the tumor while sparing healthy tissue. Also called radiosurgery and stereotactic external beam irradiation.
- radiation therapy: Radiation therapy (also called radiotherapy)uses high-energy radiation from x-rays, neutrons, and other sources to kill cancer cells and shrink tumors. It may come from a machine outside the body (external beam) or from materials that produce radiation that are placed in or near the tumor in the area where the cancer cells are found.
- radiculopathy: Any pathological (altered or caused by disease) condition of the nerve roots.
- radio necrosis: ulceration or destruction of tissue resulting from irradiation
- radioisotope: A form of a chemical element with unstable neutron number, so that it undergoes spontaneous nuclear disintegration. It's major use in biology is to trace atoms or molecules that follow the same metabolic pathway as the normal stable isotope, but that can be detected with high sensitivity by their emission of radiation.
- radionecrosis: tissue death caused by radiation.
- radionuclide: Radionuclide: An unstable form of a chemical element that radioactively decays, resulting in the emission of nuclear radiation. Also called a radioisotope
- radiosurgical ablation: Removal by a) surgery by means of a radio knife
b) surgery using precisely targeted radiation to destroy tissue without cutting -- called also stereotactic radiosurgery.
- radiotherapy: The treatment of disease by means of radiation (as X rays) -- called also radiation therapy, radium therapy.
- ranula: A cyst formed under the tongue by obstruction of a gland duct.
- rapamycin: Sirolimus, also known as rapamycin, is an immunosuppressant drug used to prevent rejection in organ transplantation; and might also be useful in the treatment of certain cancers.
- rathke: (noun)
: a pouch of ectoderm that grows out from the upper surface of the embryonic stomodeum and gives rise to the adenohypophysis of the pituitary gland --called also Rathke's pocket
- Rathke's cleft cyst: An intrasellar or suprasellar cyst lined by cuboidal epithelium from remnants of Rathke's pouch.
- Rathke's Cyst: Rathkes pouch cyst is also know an a hypophysial duct tumor and fall under the subtype of craniopharyngioma. These are histiologically bengin tumors that are assumed to originate from "cell rests" (remnants of rathkes pouch) near the pituitary gland.
- Rathke's pouch: An ectodermal upgrowth from the stomodeum (the roof of the mouth) also known as the hypophyseal pouch that is one of two parts that develops into the pituitary gland. The other part is known as the neurohypophyseal bud.
- rathkes: a pouch of ectoderm that grows out from the upper surface of the embryonic stomodeum and gives rise to the adenohypophysis of the pituitary gland -- called also Rathke's pocket
Rathke, Martin Heinrich (1793-1860), German anatomist. Rathke is regarded as one of the founders of modern embryology. In his early researches he discovered embryonic precursors of gills in the embryos of higher animals that lack gills as adults. He is best known for his discovery of branchial clefts and branchial arches in the embryos of birds and land animals. He followed the embryological history of these structures and found that the branchial clefts disappear eventually and that the blood vessels adapt themselves to the lungs. He also described and compared the development of the air sacs in birds and the larynx in birds and mammals. In 1838 he published an important study of the pituitary gland and in the following year discovered a diverticulum arising from the embryonic buccal cavity. This embryonic structure is now known as Rathke's pouch.
- RCT: Randomized controlled trial or Randomized Clinical Trial
- receptor: A cell or group of cells that receives stimuli.
- recurrent: Returning or happening time after time.
- reflex sympathetic dystrophy: A syndrome of pain and tenderness, usually to a hand or foot, associated with vasomotor instability, skin changes and rapid development of bony demineralisation (osteoporosis). Frequently will follow a localised trauma, stroke or peripheral nerve injury.
- refractory: (adjective)
1 : resistant to treatment or cure
2 : unresponsive to stimulus
3 : resistant or not responding to an infectious agent : IMMUNE
- remission: A reduction or abatement of the symptoms of a disease. Also the period during which such reduction occurs.
- remote medulla blastoma: See: medulloblastoma
- renal aneurysm: An aneurysm relating to, involving, affecting, or located in the region of the kidneys. See aneurysm.
- resect: To remove part or all of an organ or tissue.
- resected: (verb)
: to perform resection on <' an ulcer>
- resection: The cutting out of a significant portion of an organ or structure. Resection of an organ may be partial or complete.
- residue: That which remains or is left behind.
- ret mutations: See Hirschsprung disease
- retina: (noun)
: the sensory membrane that lines most of the large posterior chamber of the eye, is composed of several layers including one containing the rods and cones, and functions as the immediate instrument of vision by receiving the image formed by the lens and converting it into chemical and nervous signals which reach the brain by way of the optic nerve
- retinoblastoma: a hereditary malignant tumor of the retina that develops during childhood, is derived from retinal germ cells, and is associated with a chromosomal abnormality
- retinoic acid: An oxidized derivative of retinol believed to be the form of vitamin A that plays a role in the development and growth of bone and in the maintenance of normal epithelial structures.
- retro styloid/parapherangyl: A portion of the parapharyngeal space (PPS). The poststyloid PPS contains the internal carotid artery, internal jugular vein, cranial nerves IX to XII, sympathetic chain, and lymph nodes.
- retrovirus: any of a group of RNA-containing viruses (as HIV and the Rous sarcoma virus) that produce the enzyme reverse transcriptase to copy its genome into the DNA of another cell's chromosomes. Many cancers are caused by retroviruses.
- rhabdoid tumor: A rare but highly lethal childhood tumour found almost exclusively in infants. histopathologically, it resembles rhabdomyosarcoma but the tumour cells are not of myogenic origin. Although it arises primarily in the kidney, it may be found in other parts of the body. The rhabdoid cytomorphology is believed to be the expression of a very primitive malignant cell.
- right lateral ventricle: A portion of the brain on the right lateral side.
- right temporal lobe encephalomalacia: See: encephalomalacia
- right temporoparietal: Of or relating to the right side temporal and parietal bones or lobes
- Ritalin: See: Methylphenidate
- RNAi: RNA interference (RNAi) is a system within living cells that helps to control which genes are active and how active they are.
- roentgenogram: A photograph made with X rays.
- Romberg`s Sign: A diagnostic sign of tabes dorsalis and other diseases of the nervous system consisting of a swaying of the body when the feet are placed close together and the eyes are closed.
- RSR13: A synthetic radioenhancing agent used in conjunction with standard radiotherapy to treat brain tumors. By increasing oxygen delivery to tumors during radiation therapy, RSR13 treatment hopes to enhance the cytotoxic effect of radiation treatment.
- rt parietal lobe glioblastoma: See: glioblastoma multiforme
- rt. cerebellar menispheric cavernoma: See: cavernous hemangioma.
- sac: A soft-walled anatomical cavity usually having a narrow opening or none at all and often containing a special fluid.
- sacroco cygeal: : of, relating to, affecting, or performed by way of the region of the sacrum and coccyx
- sagital: See saggital.
- sagittal: Of, relating to, or being the sagittal suture of the skull; or of, relating to, situated in, or being the median plane of the body or any plane parallel to it (a sag·it·tal section dividing the body into unequal right and left parts).
- sagittal meningioma: A tumor of meningioma type, of, relating to, or being in area of the sagittal suture of the skull. Also, see meningioma.
- sagittal sinus: Either of two venous sinuses of the dura mater: a : one passing backward in the convex attached superior margin of the falx cerebri and ending at the internal occipital protuberance by fusion with the transverse sinus -- called also superior sagittal sinus b : one lying in the posterior two thirds of the concave free inferior margin of the falx cerebri and ending posteriorly by joining the great cerebral vein to form the straight sinus -- called also inferior sagittal sinus.
- sagittal sinus thrombus: a clot of blood formed within a blood vessel and remaining attached in the area of the sagittal sinus, either of two venous sinuses of the dura mater: a : one passing backward in the convex attached superior margin of the falx cerebri and ending at the internal occipital protuberance by fusion with the transverse sinus -- called also superior sagittal sinus b : one lying in the posterior two thirds of the concave free inferior margin of the falx cerebri and ending posteriorly by joining the great cerebral vein to form the straight sinus -- called also inferior sagittal sinus.
- sagittal sinuses: See: sagittal sinus
- sample accession: In this example, accession can be a process of increasing by addition (such as fostering a larger sample size) and it can be the process of agreeing with or consenting to participate as a sample member.
- sarcoidosis: (noun)
: a chronic disease of unknown cause that is characterized by the formation of nodules resembling true tubercles esp. in the lymph nodes, lungs, bones, and skin --called also Boeck's sarcoid
- sarcoma: Any group of tumors usually arising from connective tissue, although the term now includes some of epithelial origin. Most are malignant.
- scheuermann: Scheuermann's Disease. Osteochondrosis of the vertebral epiphyses in children.
- Scheuermann`s disease: Osteochondrosis is a disease (especially of children) in which the center of the vertebrae undergoes degeneration followed by calcification and is associated, in the active state, with pain and an exaggerated backward curve of the spinal column. Holger Werfel Scheuermann (1877-1960) was a Danish orthopedist who practiced radiology in Copenhagen. He described osteochondrosis of the vertebrae in 1920.
- scheuermanns: osteochondrosis of the vertebrae associated in the active state with pain and kyphosis
Scheuermann, Holger Werfel (1877-1960), Danish orthopedist. Scheuermann practiced radiology in Copenhagen. He described osteochondrosis of the vertebrae in 1920.
- Scheuermanns disease: Osteochondrosis of the vertebral epiphyses in children.
- Schizencephaly: A developmental disorder of the brain characterized by abnormal slits, or clefts, in the cerebral hemispheres. Individuals with clefts in both hemispheres, or bilateral clefts, are often developmentally delayed and have delayed speech and language skills. There is now a genetic origin for at least one type of schizencephaly. Other possible causes may include environmental exposures during pregnancy such as medication taken by the mother, exposure to toxins, or a vascular insult. Treatment for individuals with schizencephaly generally consists of physical therapy, treatment for seizures, and, in cases that are complicated by hydrocephalus, a shunt.
- schmidt 's disease: See: Schmidt's syndrome
- Schmidt's syndrome: 1. Unilateral paralysis of the vocal cord, the velum palati, trapezious and the sternocleidomastoid. 2. The association of primary hypothyroidism, primary adrenocortical insufficiency and insulin-dependent diabetes.
- schwannoma: A neoplasm originating from the Schwann cells (of the myelin sheath)of neurons. Also referred to as neurilemmoma.
- schwannoma.: a tumor of the myelinated sheaths of nerve fibers that consist of Schwann cells in a matrix -- called also neurinoma, schwannoma
- sclera: The dense fibrous opaque white outer coat enclosing the eyeball except the part covered by the cornea -- also called sclerotic, sclerotic coat.
- sclerosis: A condition in which a tissue has become hard and which is produced by overgrowth of fibrous tissue and other changes (as in arteriosclerosis) or by increase in interstitial tissue and other changes (as in multiple sclerosis) -- called also hardening.
- sebaceous cyst: Cyst, sebaceous: A sebaceous cyst is a rounded swollen area of the skin formed by an abnormal sac of retained excretion (sebum) from the sebaceous follicles.
- second blood brain barrier: A newly discovered brain barrier observed by scientists at Oregon Health Sciences University and the Portland Veterans Affairs Medical Center. The scientists believe that if not an actual anatomic structure, it may be an electrically charged barrier like the one that exists in the kidney that prevents some agents from crossing into the brain.
- seizure: A convulsion; a sudden, involuntary movement of the muscles.
Often a seizure is named for the kind of epilepsy it represents. Seizure types are organized according to whether the source of the seizure within the brain is localized (partial or focal onset seizures) or distributed (generalized seizures). Partial seizures are further divided on the extent to which consciousness is affected (simple partial seizures and complex partial seizures). If consciousness is unaffected, then it is a simple partial seizure; otherwise it is a complex partial seizure. A partial seizure may spread within the brain—a process known as secondary generalization. Generalized seizures are divided according to the effect on the body, but all involve loss of consciousness. These include absence, myoclonic, clonic, tonic, tonic-clonic, and atonic seizures.
- seizure medications: Medications given to try and stop seizures from happening.
- seizures: (noun)
: a sudden attack (as of disease)
- sella: A saddle-shaped depression.
- sella turcica: Small fossa which contains the pituitary gland.
- sellar: (adjective)
: of, relating to, or involving the sella turcica
- sensory strip: The postcentral gyrus, also called the primary sensory area or the sensory strip, is located in an area of the parietal lobe. This area receives sensory feedback from joints and tendons in the body. The parietal lobe is associated with sensation, including the sense of touch, kinesthesia, perception of warmth and cold, and of vibration. It is also involved in writing and in some aspects of reading.
- sensory-motor polyneuropathy: Polyneuropathy is a neurological disorder that occurs when many peripheral nerves throughout the body malfunction simultaneously. Acute polyneuropathy can have various causes, including infections, autoimmune reactions, toxins, certain drugs, and cancer.
- sepsis: (noun)
: a toxic condition resulting from the spread of bacteria or their products from a focus of infection; esp : SEPTICEMIA
- septum: A dividing wall or membrane especially between bodily spaces or masses of soft tissue.
- septum pellucidum: The septum pellucidum itself probably has no special functional importance. It is made up of two thin sheets of mostly glial-like elements that abut each other in the midline and have a potential space between them. Those sheets also separate the left and right lateral ventricles from each other. At the base of the sheets rostrally, however, are the septal nuclei, which are important components of the limbic system.
- septum pellucidum cyst: A cyst in the area of the septum pellucidum.
- sequela: A sequela, is a pathological condition resulting from a disease, injury, or other trauma. Other examples of sequelae include those following neurological injury; including aphasia, ataxia, hemi- and quadriplegia, and any number of other changes that may be caused by a neurological insult.
- sequelae: An after effect of disease or injury, a scecondary result.
- sera: Inflected Form(s): plural serums or se·ra /-&/
: the watery portion of an animal fluid remaining after coagulation: a (1) : the clear yellowish fluid that remains from blood plasma after fibrinogen, prothrombin, and other clotting factors have been removed by clot formation -- called also blood serum (2) : ANTISERUM b : a normal or pathological serous fluid (as in a blister)
- serotonin: A neurotransmitter and hormone (176 kD), found in vertebrates, invertebrates and plants. It is synthesised from the amino acid tryptophan by enterochromaffin cells in the gut and bronchi. It is metabolised to 5-HIAA in the liver and then excreted in the urine. Studies show that low levels of the brain chemical serotonin can in part lead to an overall insensitivity to future consequences, setting off impulsive and aggressive behaviors. Insufficient serotonin levels have also been linked to depression, migraines, eating disorders, jaw tension, weight, and more.
- seventh nerve: See "seventh cranial nerve."
- shank: 1. The part of the leg from the knee to the foot; the shin; the shin bone; also, the whole leg. "His youthful hose, well saved, a world too wide For his shrunk shank." (Shak)
2. The part of the sole beneath the instep connecting the broader front part with the heel.
To fall off, as a leaf, flower, or capsule, on account of disease affecting the supporting footstalk; usually followed by off.
- shark cartilage: A highly controversial substance reported by some to have anti-cancer effects.
- shingles: (noun)
: an acute viral inflammation of the sensory ganglia of spinal and cranial nerves associated with a vesicular eruption and neuralgic pain and caused by reactivation of the herpesvirus causing chicken pox --called also herpes zoster, zona, zoster
- shunt: A tube or device implanted in the body to redirect body fluid from one cavity to another.
- shunts: (noun)
1 : a passage by which a bodily fluid (as blood) is diverted from one channel, circulatory path, or part to another; esp : such a passage established by surgery or occurring as an abnormality
2 a : a surgical procedure for the establishment of an artificial shunt --see PORTACAVAL SHUNT
b : a device (as a narrow tube) used to establish an artificial shunt
-- shunt (verb)
- side effects: A consequence other than the one(s) for which an agent or measure is used, as in the adverse side effects caused by a drug, especially on a tissue or organ system other than the one sought to be benefited by its administration.
- signaling pathways: Cell signaling is part of a complex system of communication that governs basic cellular activities and coordinates cell actions. Systems biology research helps us to understand the underlying structure of cell signaling networks (pathways)and how changes in these networks may affect the transmission and flow of information
- silvian: See: Parinaud's syndrome
- silvian fissure: A deep fissure of the lateral aspect of each cerebral hemisphere that divides the temporal from the parietal and frontal lobes.
- sinusitis: Sinusitis is an inflammation of the paranasal sinuses, which may or may not be as a result of infection, from bacterial, fungal, viral, allergic or autoimmune issues. Newer classifications of sinusitis refer to it as rhinosinusitis, taking into account the thought that inflammation of the sinuses cannot occur without some inflammation of the nose as well (rhinitis).
There are several paired paranasal sinuses, including the frontal, ethmoid, maxillary and sphenoid sinuses. The ethmoid sinuses can also be further broken down into anterior and posterior, the division of which is defined as the basal lamella of the middle turbinate. In addition to the acuity of disease, sinusitis can be classified by the sinus cavity which it affects:
Maxillary sinusitis: can cause pain or pressure in the maxillary (cheek) area (e.g., toothache, headache)
Frontal sinusitis: can cause pain or pressure in the frontal sinus cavity (located behind/above eyes), headache
Ethmoid sinusitis: can cause pain or pressure pain between/behind eyes, headache
Sphenoid sinusitis: can cause pain or pressure behind the eyes, but often refers to the vertex of the head
Recent theories of sinusitis indicate that it often occurs as part of a spectrum of diseases that affect the respiratory tract (i.e., the "one airway" theory) and is often linked to asthma. All forms of sinusitis may either result in, or be a part of, a generalized inflammation of the airway so other airway symptoms such as cough may be associated with it.
- sixth nerve palsey: Paralysis (palsy) of the abducens nerve, or either of the sixth pair of cranial nerves which are motor nerves, that arise beneath the floor of the fourth ventricle, and supply the lateral rectus muscle of each eye -- called also abducent nerve, sixth cranial nerve.
- skin cancer: A malignant growth on the skin.
- skull: The skull is a bony structure found in the human head which supports the structures of the face and protects the head against injury. The adult skull is normally made up of 22 bones. Except for the mandible (jaw bone), all of the bones of the skull are joined together by sutures, rigid articulations permitting very little movement. Eight bones form the neurocranium (braincase) including the frontal, parietals, occipital bone, sphenoid, temporals and ethmoid. Fourteen bones form the splanchnocranium, the bones supporting the face. Encased within the temporal bones are the six ear ossicles of the middle ears, though these are not part of the skull. The hyoid bone, supporting the tongue, is usually not considered as part of the skull either, as it does not articulate with any other bones. The skull is a protector of the brain.
The skull contains the sinus cavities, which are air-filled cavities lined with respiratory epithelium, which also lines the large airways. The exact functions of the sinuses are unclear; they may contribute to decreasing the weight of the skull with a minimal decrease in strength, or they may be important in improving the resonance of the voice.
- small densly calcified meningioma: See: calcification; meningioma
- somatomedin: A peptide synthesized in the liver and probably the kidney that is capable of stimulating certain anabolic processes in bone and cartilage such as synthesis of DNA and RNA and protein.
- sonogram: : an image produced by ultrasound -- called also echogram, ultrasonogram
- SPECT: (abbreviation)
single photon emission computed tomography
: an instrument for forming and examining optical spectra
-- spec*tro*scop*ic (adjective)
- spectroscopy: (noun)
: MASS SPECTROMETRY
-- mass spectroscope (noun)
- sphenoid: of, relating to, or being a compound bone of the base of the cranium of various vertebrates formed by the fusion of several bony elements with the basisphenoid and in humans consisting of a median body from whose sides extend a pair of broad curved winglike expansions in front of which is another pair of much smaller triangular lateral processes while ventrally two large deeply cleft processes extend downward -- see GREATER WING, LESSER
- sphenoid wings: (adjective)
: of, relating to, or being a compound bone of the base of the cranium formed by the fusion of several bony elements with the basisphenoid and in humans consisting of a median body from whose sides extend a pair of broad curved winglike expansions in front of which is another pair of much smaller triangular lateral processes while ventrally two large deeply cleft processes extend downward --see GREATER WING, LESSER WING
- spina bifida: a congenital cleft of the spinal column with hernial protrusion of the meninges and sometimes the spinal cord
- spinal fluid: see cerebrospinal fluid
- spinal leptomeningeal: See: leptomeningeal
- spinal stenosis: See stenosis.
- spinal tap: see lumbur puncture
- spindle cell brain tumor: A tumor in which the cells are somewhat spindle-shaped.
- splanchnocranium cancer: Cancer of the facial skeleton
- split brain syndrome: A condition where information normally received by one hemisphere of the brain and passed to the other for processing does not take place.
- split brain theory: The theory that the right and left cerebral hemispheres are specialized for some behaviors. The hemispheres communicate with each other through a thick band of 200-250 million nerve fibers called the corpus callosum. It is well-known that the right side of the brain controls muscles on the left side of the body and the left side of the brain controls muscles on the right side of the body.
- spongioblastoma: A malignant tumor of the central nervous system and usually of a cerebral hemisphere -- called also glioblastoma.
- squamous: Scaly or platelike.
- squamous cell: See Squamous Cell Carcinoma.
- squamous cell carcenoma: Squamous cell carcinoma. A malignant growth originating from a squamous cell. This form of cancer can be seen on the skin, lips, inside the mouth, throat or oesophagus.
- squamous cell carcinoma: A malignant growth originating from a squamous cell. This form of cancer can be seen on the skin, lips, inside the mouth, throat or esophagus.
- SSRI: Selective serotonin reuptake inhibitors or serotonin-specific reuptake inhibitor. (SSRIs) are a class of compounds typically used as antidepressants in the treatment of depression, anxiety disorders, and some personality disorders
- st annes glioma: The St. Anne-Mayo grading system is one of several tumor grading systems, the most recognizable being the WHO grading system. The St. Anne-Mayo system uses four morphologic criteria to assign a grade:
a) nuclear atypia
c) endothelial proliferation
The St. Anne-Mayo grading has four categories of tumors:
Grade 1 tumors do not meet any of the criteria.
Grade 2 tumors meet one criterion, usually nuclear atypia.
Grade 3 tumors meet two criteria, usually nuclear atypia and mitosis.
Grade 4 tumors meet three or four of the criteria.
- stable disease: Cancer that is not growing or shrinking.
- STAGE: The extent to which cancer has spread. Usually denoted by a number from Stage 1 (least severe) to Stage 4 (more advanced). Different lymphoma types have different criteria for staging.
- stage 4 astrocytoma: See: glioblastoma multiforme
- Stage IV Glioblastoma: See: glioblastoma multiforme
- staph infection: A group of infections caused by bacteria of the staphylococcus family. They grow in grape like clusters and cause skin infections and serious internal disorders.
- stat: Abbreviation for immediately. Something is requested to be done immediately such as test results or values or an evaluation of some kind.
- stem cell: Any precursor cell.
- stem cells:
: an unspecialized cell that gives rise to differentiated cells
- stenosis: plural -no*ses
: a narrowing or constriction of the diameter of a bodily passage or orifice
- stereognosis: (noun)
: ability to perceive or the perception of material qualities (as form and weight) of an object by handling or lifting it : tactile recognition
- stereotactic: This refers to the localization in 3 dimentional space of a tumor. It can refer to surgery or radiation. Click here for details.
- stereotactic biopsy: A surgical procedure that uses advanced computers to help guide the surgeon to remove a small piece of tumor through a small incision in the head. It is used for diagnostic purposes - to find out what is causing the abnormality on the brain scans.
- stereotactic brain surgery: Precise positioning in three dimensional space. Refers to surgery or radiation therapy directed by various scanning devices.
- stereotactic radiosurgery: A form of radiation that uses multiple beams of radiation that are 'focused ' only on the tumor. The advantage is the tumor gets a high dose of radiation - but the surrounding normal brain gets a very little dose. This can be done with a few different machines: Gamma Knife, Linac, Proton Beam, Peacock system and others. It is usually done as a single 'shot', but can be broken up into multiple treatments (fractionated).
- sternomastoid: (noun)
- sternomastoid tumor: In human anatomy, the sternocleidomastoid muscle, also known as sternomastoid and commonly abbreviated as SCM, is a paired muscle in the superficial layers of the anterior portion of the neck. It acts to flex and rotate the head.
- steroid: Synthetic anti-inflammatory compounds used to reduce the ammount of swelling within brain, or other, tissue.
- strabismus: The inability of one eye to attain focused vision with the other because of imbalance of the muscles of the eyeball -- called also heterotropia, squint.
- streptozocin: An antibiotic that is produced by stretomyces achromogenes. It is used as an antineoplastic agent and to induce diabetes in experimental animals.
- stress: 1 a : a force exerted when one body or body part presses on, pulls on, pushes against, or tends to compress or twist another body or body part ; especially : the intensity of this mutual force commonly expressed in pounds per square inch b : the deformation caused in a body by such a force
2 a : a physical, chemical, or emotional factor that causes bodily or mental tension and may be a factor in disease causation b : a state of bodily or mental tension resulting from factors that tend to alter an existent equilibrium
3 : the force exerted between teeth of the upper and lower jaws during mastication
- striations: A minute groove, scratch, or channel especially when one of a parallel series.
- striatum: Inflected Form(s): plural corpora stri·a·ta /-'At-&/
: either of a pair of masses of nerve tissue which lie beneath and external to the anterior cornua of the lateral ventricles of the brain and form part of their floor and each of which contains a caudate nucleus and a lentiform nucleus separated by sheets of white matter to give the mass a striated appearance in section
- stroke: The sudden diminution or loss of consciousness, sensation, and voluntary motion caused by rupture or obstruction (as by a clot) of an artery of the brain -- called also apoplexy.
- SU-101: An experimental drug whose treatment concept is based on Platelet-Derived Growth Factor (PDGF). Brain tumor cells grow and divide by responding to growth factors. PDGF has been found to be important to the growth of malignant brain tumors such as glioblastoma multiforme . PDGF binds to special "antennas" on the tumor cell surface called receptors and these receptors relate the PDGF signal to the internal machinery of tumor cells. The result is runaway growth of brain tumors. SU101 is a drug that counteracts PDFG activity on receptors by blocking the receptor's ability to relate growth signals internally. The theory is that this will stop or inhibit the growth of brain tumors. As of May 1999 this drug is currently in a randomized double-blind study comparing it to procarbazine.
- SU-5146: A drug currently in clinical trials that prevents the formation of new blood vessels (angiogenesis) required for tumor growth by blocking the Flk-1/KDR receptor found in the endothelial cells of blood vessels.
- SU101: SU101 is a chemotherapy under study by the SUGEN, Inc. corporation. It is a small molecule inhibitor that blocks the signaling of the platelet-derived growth factor (PDGF) receptor. The PDGF receptor is believed to be the driving oncogene (a gene having the potential to cause a normal cell to become cancerous) in subsets of brain, prostate, ovarian and non-small cell lung tumors.
- sub-arachnoid cyst: See subarachnoid cyst.
- subarachnoid: A delicate fibrous membrane forming the middle of the three coverings of the central nervous system.
- subarachnoid cyst: A cyst in the subarachnoid.
- subarachnoid hemmorage: Subarachnoid hemorrhage: Bleeding within the head into the space between two membranes that surround the brain. The bleeding is beneath the arachnoid membrane and just above the pia mater. (The arachnoid is the middle of three membranes around the brain while the pia mater is the innermost one.)
The subarachnoid space is a potential space. It is normally filled with cerebrospinal fluid. With a subarachnoid bleed, the cerebrospinal fluid in the subarachnoid space is bloody.
Subarachnoid hemorrhages are typically acute (sudden). They may follow a head injury or rupture of a blood vessel in the central nervous system (brain and spinal cord) as, for example, because of an aneurysm in the vessel.
Nearly half of people admitted to a hospital with a subarachnoid hemorrhage die within a month. Many of the survivors are left with severe disabilities.
The first-degree relatives of patients with subarachnoid hemorrhage are more likely to develop the condition than those who do not have a family history of it. Smoking, alcohol abuse, and high blood pressure are risk factors for subarachnoid hemorrhage.
- subcortical: (adjective)
: of, relating to, involving, or being nerve centers below the cerebral cortex
-- sub*cor*ti*cal*ly (adverb)
- subdural: See Subdural Hematoma.
- subdural hematoma: An accumulation of blood in the subdural space.
- subdural hemmorrage: See: subdural hematoma.
- subdural hygroma: Subdural hygromas or effusions consist of collections of cerebrospinal fluid in the subdural spaces of the brain, presumably due to a traumatic arachnoid tear or they may also develop following ventricular shunting. They may accumulate slowly during the first few days following head trauma, especially in children.
- subdural space: (noun)
: a fluid-filled space or potential space between the dura mater and the arachnoid
- subependymal: The subependymal zone is a cell layer surrounding the lateral ventricles in the brain. This region contains adult neural stem cells which have the potential to generate new neurons and glial cells. It is an adult version of the embryonic forebrain germinal zone.
Ilias Kazanis at the University of Cambridge compares the subependymal zone to a beating heart which "continuously sends new cells to different areas of the brain: neurons to the olfactory bulbs and glial cells to the cortex and the corpus callosum."
- subependymoma: An ependymoma in which there is a diffuse proliferation of subependymal fibrillary astrocytes among the ependymal tumor cells. A few are malignant and others cause obstructive hydrocephalus, but many are clinically silent and are discovered only at autopsy.
- subpial: Situated or occurring beneath the pia mater, the delicate and highly vascular membrane of connective tissue investing the brain and spinal cord, lying internal to the arachnoid and dura mater, dipping down between the convolutions of the brain, and sending an ingrowth into the anterior fissure of the spinal cord.
- sudo: See pseudotumor cerebri.
- Sudo tumor: See: pseudotumor cerebri
- Sudo tumor cerebi: See: pseudotumor cerebri
- sudo tumor cerebri: See: pseudotumor cerebri.
- sudo tumour: See: pseudotumor cerebri
- sudotumorcerebrum: See pseudotumor cerebri.
- sulcal: of or relating to a sulcus
- sulcal region: A groove or furrow, as one of the grooves on the surface of the cerebrum.
- sulci: See: Sulcus
- sulcus: In neuroanatomy, a sulcus is a depression or fissure in the surface of the brain. It surrounds the gyri, creating the characteristic appearance of the brain in humans and other large mammals.
- sulcus: (noun)
: FURROW, GROOVE; esp : a shallow furrow on the surface of the brain separating adjacent convolutions --compare FISSURE lc
- sunburst: A pattern in the form of rays diverging from a central point.
- superficial: Superficial describes objects near the body's surface as compared to other objects that may be deep. For example, skin is a superficial structure of the body and muscles are deep to skin.
- Superior Colliculus: : either member of the anterior and higher pair of corpora quadrigemina that together constitute a primitive center for vision -- called also optic lobe, optic tectum -- compare INFERIOR COLLICULUS
- superior sagittal sinus thrombosis: The formation or presence of a blood clot within a blood vessel located in or near the superior saggital sinus.
- supra nuclear palsey: An uncommon neurological disorder that is of unknown etiology, that typically occurs from late middle age onward, and that is marked by loss of voluntary vertical eye movement, muscular rigidity and dystonia of the neck and trunk, pseudobulbar paralysis, bradykinesia, and dementia -- called also supranuclear palsy.
- supra sellular: See suprasellar and sella turcica.
- supra-nuclear palsey: A progressive neurological disease usually of the fifth decade characterised by supranuclear ophthalmoplegia especially paralysis of downward gaze, pseudobulbar palsy, gait disturbance, dysathria, truncal dystonia, memory and personality deterioration, and dementia.
- suprachiasma: Suprachiasmatic. Situated or occurring above the optic chiasma.
- suprachiasmatic nucleus: A small group of neurons situated immediately dorsal to the optic chiasma -- abbreviation SCN.
: situated or rising above the sella turcica
-- used chiefly of tumors of the hypophysis
- supratentorial: Above a tentorium.
- surgery: An operation.
- survival rate: The typical or average length of time one continues to live after being diagnosed with a terminal disease or illness.
- suto cyst: See: pseudotumor cerebri; cyst
- suto tumber: See: pseudotumor cerebri.
- suto tumer: See: pseudotumor cerebri.
- suto tumor: See pseudotumor cerebri.
- suto tumor cerebri: See pseudotumor cerebri.
- swelling: Swelling is the enlargement of organs caused by accumulation of excess fluid in tissues, called edema.
It can occur throughout the body (generalized), or a specific part or organ can be affected (localized). Swelling is considered one of the five characteristics of inflammation; along with pain, heat, redness, and loss of function. A body part may swell in response to injury, infection, or disease, as well as because of an underlying lump, or tumor in the case of brain disease. Generalized swelling, or massive edema (also called anasarca), is a common sign in severely ill people. Although slight edema may be difficult to detect to the untrained eye, especially in an overweight person, massive edema is very obvious.
Brain edema is often treated with steroids, particularly Decadron. A newer drug, Xerecpt, is being tested. Some brain tumor patients use boswellia, a supplement, with some success. Severe brain edema is a serious condition that should be adequately controlled/treated.
- sylvian: of or relating to the sylvian fissure
- sylvian fissure: A prominent groove in the brain passing between the temporal and frontal lobes.
- sylvian+fissure: A deep fissure of the lateral aspect of each cerebral hemisphere that divides the temporal from the parietal and frontal lobes -- called also fissure of Sylvius, lateral fissure, lateral sulcus.
- sympathomimetic: Sympathomimetic drugs are substances that mimic the effects of the sympathetic nervous system, such as catecholamines, epinephrine (adrenaline), norepinephrine (noradrenaline), dopamine, etc.
- symptoms: Symptoms of brain tumors may include headache, blurred vision, vomiting or mental dulling. Symptoms may vary from person to person and may include other symptoms as well. Motor control may be affected also.
- symptons of tumor: This appears to be a misspelling of symptoms. Please see that entry.
- symtoms: This appears to be a misspelling of symptoms. Please see that entry.
- synapse: The point at which a nervous impulse passes from one neuron to another in the brain.
- synaptophysin: Synaptophysin is a membrane glycoprotein of synaptic vesicles that is ubiquitously expressed in all neurons and, in addition, in many endocrine cells. It is currently the most widely used tumor marker for nerve terminals and probably the best marker for the pathologist in differentiating neuroendocrine tumors.
- syncope: Syncope: Partial or complete loss of consciousness with interruption of awareness of oneself and ones surroundings. When the loss of consciousness is temporary and there is spontaneous recovery, it is referred to as syncope or, in nonmedical quarters, fainting. Syncope accounts for one in every 30 visits to an emergency room. It is pronounced sin-ko-pea.
Syncope is due to a temporary reduction in blood flow and therefore a shortage of oxygen to the brain. This leads to lightheadedness or a "black out" episode, a loss of consciousness. Temporary impairment of the blood supply to the brain can be caused by heart conditions and by conditions that do not directly involve the heart:
Non-cardiac causes: Syncope is most commonly caused by conditions that do not directly involve the heart. These conditions include:
Postural (orthostatic) hypotension: Drop in blood pressure due to changing body position to a more vertical position after lying or sitting;
Dehydration causing a decrease in blood volume.
Blood pressure medications leading to low blood pressure.
Diseases of the nerves to the legs in older people (especially with diabetes or Parkinson's disease) when poor tone of the nerves of the legs draws blood into the legs from the brain.
Brain stroke or "near-stroke" (transient ischemic attack).
A migraine attack.
Fainting after certain situations (situational syncope) such as:
Urinating (micturition syncope),
Defecating (defecation syncope),
Swallowing (swallowing syncope), or
Coughing (cough syncope)
that trigger a reflex of the involuntary nervous system (the vasovagal reaction) that slows the heart and dilates blood vessels in the legs and cause one to feel nausea, sweating, or weakness just before losing fainting.
Cardiac causes: Heart conditions that can cause syncope or fainting due to temporary loss of consciousness include:
Abnormal heart rhythms (heart beating too fast or too slow).
Abnormalities of the heart valves (aortic stenosis or pulmonic valve stenosis).
High blood pressure in the arteries supplying the lungs (pulmonary artery hypertension).
Tears in the aorta (aortic dissection).
Widespread disease of the heart muscle (cardiomyopathy).
To be sure, many of the causes of temporary loss of consciousness can be detected by a careful history. Dizziness after standing up in an older person suggests postural hypotension. Temporary loss of consciousness after urinating, defecating, or coughing suggests situational syncope. Cardiac causes of temporary loss of consciousness such as aortic stenosis or cardiomyopathy are suggested by the occurrence of the event during exercise. Signs of weakness localized to certain areas of the body with temporary loss of consciousness suggest stroke.
The blood pressure and pulse are tested in the lying, sitting, and standing positions. Unequal blood pressures in each arm is a sign of aortic dissection. The heart is examined with a stethoscope to listen for sounds that can indicate valve abnormalities. The nervous system is tested for sensation, reflexes, and motor function to detect conditions of the nerves and brain. An EKG is done to check for abnormal heart rhythms. Other tests may include echocardiograms, rhythm monitoring tests (heart event recorders), and electrophysiologic testing for abnormalities of the heart's electrical system.
When heart conditions are not suspected, tilt-table testing can be used to detect causes of temporary loss of consciousness. Tilt-table testing involves placing the patient on a table with a foot-support. The table is tilted upward and blood pressure and pulse is measured while symptoms are recorded in various positions.
No treatment is needed for many non-cardiac causes of syncope (such as postural hypotension, vasovagal reaction, and situational syncope). The person regains consciousness by simply sitting or lying down. The person is thereafter advised to avoid trigger situations, to not strain while eliminating, to sit when coughing, to lie down for blood drawing, etc.
Older people should have their medications reviewed and caution is advised to slow the process of changing positions from lying to standing. This simple technique can allow the body to adjust to the new position (as the nerves to circulation of the legs adjust slower in older persons
- synovial sarcoma: Also called synovioma, a rare cancer that begins in synovial tissue. Synovial tissue can be found in tendons (tissues that connect muscle to bone), bursae (fluid-filled, cushioning sacs found in spaces between tendons, ligaments, and bones), and the cavity (hollow enclosed area) that separates the bones of a freely movable joint, such as the knee or elbow. Synovial sarcomas occur mainly in the arms and legs, where they tend to arise in the area of large joints, especially the knee region. Less frequently, the disease develops in the head and neck and in the trunk.
- syringomyelia: A chronic progressive disease of the spinal cord associated with sensory disturbances, muscle atrophy, and spasticity.
- system: a group of body organs that together perform one or more vital functions -- see CIRCULATORY SYSTEM, NERVOUS SYSTEM, REPRODUCTIVE SYSTEM, RESPIRATORY SYSTEM b : the body considered as a functional unit
2 : a manner of classifying, symbolizing, or schematizing
- systemic: Of, relating to, or common to a system: as affecting the body generally.
- T-cells: A type of lymphocyte (white blood cell). They are an important part of the immune system. There are two main types of T-cells. T-4 cells, also called CD4+, are helper cells. They lead the attack against infections. T-8 cells, (CD8+), are suppressor cells that end the immune response. CD8+ cells can also be killer cells that kill cancer cells and cells infected with a virus.
- T1 relaxation time: In magnetic resonance imaging (MRI) T1 is the time taken for protons which have been flipped to return to their original state.
- T2: Protons in a magnetic field have a microscopic magnetization, and act like toy tops that wobble as they spin. MR Imaging is based on the observation of the relaxation that takes place after the RF pulse has stopped. The return of the excited nuclei from the high energy to the low energy state is associated with the loss of energy to the surrounding nuclei. From a medical perspective, it means that MR Imaging can provide multiple channels to observe the same anatomy. For instance, different tissues appear different in T1 and T2 images. White matter appears in a light grey in T1 and a dark grey in T2. Grey matter appears grey in both T1 and T2images. The Cerebro-Spinal Fluid (CSF) appears black in T1 and white in T2. The background of the image (air) will appear black in both images.
- T2 relaxation time: In magnetic resonance imaging (MRI) this is the transverse relaxation time. After a 90 degree flip the net magnetic field resonates about the transverse plane and generates a current (the MR signal). The protons which are originally in phase, slowly go out of phase and eventually neutralize out each other. The current stops. The T2 relaxation time is the time taken for this to happen.
- tachycardia: Excessive rapidity in the action of the heart, the term is usually applied to a heart rate above 100 per minute and may be qualified as atrial, junctional (nodal) or ventricular and as paroxysmal.
- tacrine: A cholinesterase inhibitor (see definition) that crosses the blood-brain barrier. Tacrine has been used to counter the effects of muscle relaxants, as a respiratory stimulant, and in the treatment of alzheimer's disease and other central nervous system disorders.
- tactile sensation: Tactile means "pertaining to touch."
- tamoxifen: An anticancer agent that belongs to the family of drugs called antiestrogens. It is also known as an antineoplastic. Click here for more information. Click here for even more information.
- Taxol: An anticancer drug that belongs to the yew tree family of drugs called mitotic inhibitors. Also known as paclitaxel.
- tectal: Of or relating to the tectum. See tectum.
- tectal glioma: Usually a low-grade astrocytoma that enlarges the tectum and may completely obliterate the aqueduct causing hydrocephalus.
- tectum: (noun)
1 : a bodily structure resembling or serving as a roof
2 : the dorsal part of the midbrain including the corpora quadrigemina
- teeth: teeth
pl of TOOTH
- Temadol: TEMODAR or Temozolomide, an imidazotetrazine derivative. A chemotherapy agent for the treatment of anaplastic astrocytoma brain tumors. The chemical name of temozolomide is 3,4-dihydro-3-methyl-4-oxoimidazo[5,1-d]-as-tetrazine-8-carboxamide.
- temador: See temodar.
- Temodal: An anticancer drug that interferes with the DNA in cancer cells and prevents them from growing. Also known as temozolomide. Click here for more information. Click here for even more information.
- Temodar: Temodar. Temodal. Temozolomide. An oral cytotoxic alkylating agent, is the lead compound in a new class of compounds known as imidazotetrazines. Cytotoxic agents are designed to prevent the replication of cells that divide rapidly, including those in tumors. Recently (1999)received FDA approval for the treatment of anaplastic astrocytoma brain tumors.
- temozolomide: Same as Temodal.
- temporal: Pertaining to the lateral region of the head, superior to the zygomatic arch. Also means temporary.
- temporal lobe: The lateral region of the cerebrum, below the lateral fissure. Within the temporal lobe of the brain is the center for smell, some association areas for memory and learning, and a region where choice is made of thoughts to express.
- temporal lobe epilepsy: temporal-lobe: Epilepsy characterized by abnormal electrical activity in the temporal lobe of the brain. This activity does not cause grand mal seizures, but rather causes unusual behaviors and patterns of cognition. Seizures in temporal-lobe epilepsy often start in childhood and may present as:
Simple partial seizures with a preserved awareness of self and surroundings (also known as an aura or warning). Patients commonly experience a variety of psychic, gustatory, olfactory, and autonomic symptoms.
Complex partial seizures in which awareness is impaired. Patients are disabled. They lose awareness and tend to have a motionless stare accompanied by automatisms -- stereotyped, repetitive, involuntary movements such as lip smacking, chewing, picking at objects, scratching, and gesturing.
Generalized convulsions also occur in some temporal-lobe epilepsy patients.
Temporal-lobe epilepsy is difficult to diagnose, because temporal lobe seizures may not show up on an EEG. Diagnosis may instead be by observation of symptoms or through the use of brain imaging technology.
Temporal lobe epilepsy can be treated with the same types of anti-seizure medications used for other forms of epilepsy. However, such medical treatment may be futile. Surgery is an important option. In a randomized controlled trial, a year after surgery 58% of patients treated surgically as compared with 8% of those treated medically were free of complex partial and generalized seizures, and the quality of life was significantly better in the surgical group. Surgery may thus control seizures and preclude unnecessary disability
- temporal lobe hyperplasia: An abnormal or unusual increase in the elements composing a part (as cells composing a tissue) of the temporal lobe.
- temporoparietal: Of or relating to the temporal and parietal bones or lobes.
- Tentorial: The straight sinus (also known by the alternate anatomical term tentorial sinus), within the human head is an area beneath the brain which allows blood veins to span the area, from the center of the head towards the back.
- tentorium: Dura mater that resembles a tent and supports the occipital lobes and covers the cerebellum
- teratogenic: (adjective)
: of, relating to, or causing developmental malformations <' substances> <' effects>
- teratoma: A tumor, sometimes found in newborn children, which is made up of a heterigenous mixture of tissues, as of bone, cartilage and muscle.
- Terratoma: Teratoma. A tumor derived from more than one embryonic layer and made up of a heterogeneous mixture of tissues (as epithelium, bone, cartilage, or muscle).
- test: (noun)
1 : a critical examination, observation, evaluation, or trial
2 : a means of testing: as
a : (1) : a procedure or reaction used to identify or characterize a substance or constituent (2) : a reagent used in such a test
b : a diagnostic procedure for determining the nature of a condition or disease or for revealing a change in function --see BLOOD TEST, DICK TEST, PATCH TEST, TUBERCULIN TEST, WASSERMANN TEST
c : something (as a series of questions) for measuring the skill, knowledge, intelligence, capacities, or aptitudes of an individual or group --see INTELLIGENCE TEST, PERSONALITY INVENTORY
3 : a result or value determined by testing
-- test (adjective or verb)
- testosterone: : a male hormone that is a crystalline hydroxy steroid ketone C19H28O2 produced primarily by the testes or made synthetically and that is the main androgen responsible for inducing and maintaining male secondary sex characteristics
- thalamus: The part of the brain surrounding the third ventricle.
- thalidomide: A drug which is being studied in clinical trials for the treatment of a number of conditions and diseases, including cancer. Doctors believe that thalidomide inhibits the growth of new blood vessles that feed a tumor. Click here for more information.
- thalilomide: Thalidomide. Sedative drug that when taken between 3rd and 5th week of pregnancy produced a range of malformations of the foetus, in severe cases complete absence of limbs (amelia) or much reduced limb development (phocomelia). A teratogen. Currently being studied in the treatment of brain tumors for its antiangiogenic properties.
- Thallium: A radioactive isotope used as a diagnostic aid.
- thalmic cyst: A cyst in the area of the thalamus.
- thalmic tumor: tumor in the area of the thalamus
- thalmus tumors: See: thalamus; tumor
: a bitter alkaloid closely related to caffeine that is used as a diuretic, myocardial stimulant, and vasodilator
- theoplastoma: See: glioblastoma multiforme
- therapy: The treatment of disease.
- thioguanine: (6-TG), antimetabolic antineoplastic (also tioguanine).
- third ventrical: Four connected cavities called ventricles contain structures called choroid plexus. The choroid plexus produces spinal fluid, which flows through the ventricles and meninges surrounding the brain and spinal cord.There are two lateral ventricles, one in each cerebral hemisphere. The third ventricle is beneath the corpus callosum and surrounded by the thalamus.
- Third Ventricle: The third ventricle is one of four connected fluid-filled cavities comprising the ventricular system within the human brain. It is in the midline, between the left and right lateral ventricles and is filled with cerebrospinal fluid (CSF).
- thrombocytopenia: A decrease in the number of platelets.
- thrombosis: The formation, development or presence of a thrombus.
- thymidine kinase: An enzyme that is involved in DNA replication and that increases greatly during infection with some viruses (as the herpesvirus causing herpes simplex) and during periods of increased growth rate (as in liver regeneration).
- thymus: Also, thymus gland. A glandular structure of largely lymphoid tissue that functions in cell-mediated immunity by being the site where T cells develop, that is present typically in the upper anterior chest or at the base of the neck, that arises from the epithelium of one or more embryonic branchial clefts, and that tends to disappear or become rudimentary in the adult.
- thyroglossal : of, relating to, or originating in the thyroglossal duct
- thyroglossal duct cyst: A cyst located in or near the temporary duct connecting the embryonic thyroid gland and the tongue.
- thyroid: (noun)
1 : a large bilobed endocrine gland that arises as a median ventral outgrowth of the pharynx, lies in the anterior base of the neck, and produces esp. the hormones thyroxine and triiodothyronine --called also thyroid gland
2 : a preparation of the thyroid gland containing approximately 1/10 percent of iodine combined in thyroxine and used in treating thyroid disorders -- called also thyroid extract
- TIA: Function: abbreviation
transient ischemic attack
- tic: 1 : local and habitual spasmodic motion of particular muscles especially of the face : TWITCHING
2 : a habitual usually unconscious quirk of behavior or speech
- ticdeleroux: Tic douloureux. Also referred to as trigeminal neuralgia. An intense paroxysmal (sudden) neuralgia (pain radiating along the course of one or more nerves) involving one or more branches of the trigeminal nerve.
- tinnitus: A noise in the ears such as ringing, buzzing, roaring or clicking.
- tiny para falcine calcified densities: See: calcification
- tomography: A method of producing a three-dimensional image of the internal structures of a solid object.
- tonus: A state of partial contraction that is characteristic of normal muscle, is maintained at least in part by a continuous bombardment of motor impulses originating reflexly, and serves to maintain body posture -- also called muscle tone.
- topotecan: This alkaloid chemotherapy drug is a derivative of the drug camptothecin, which was originally isolated from a Chinese tree, Camptotheca acuminata but has also been found in the nothapodytes tree (Nothapodytes foetida).Topotecan is a DNA topoisomerase I inhibitor and is used to treat advanced ovarian cancer, among other cancers.
- toremifene: Toremifene or Fareston is an estrogen antagonist used to treat metastatic breast cancer.
- toxoplasmosis: An infection caused by a single-celled parasite named Toxoplasma gondii that may invade tissues and damage the brain, especially of the fetus and newborn.
The parasite Toxoplasma gondii is very common (more than 60 million people in the US carry it) but few are aware of it because the immune system often keeps the parasite from causing illness.
The usual symptoms of toxo are similar to flu with fever, fatigue, headache, swollen lymph glands (lymphadenopathy), and muscle aches and pains (myalgia) that may last for a few days to several weeks.
Toxo can be contracted by touching the hands to the mouth after gardening, cleaning a cat's litter box, or anything that came into contact with cat feces. Toxo can also be contracted by eating raw or partly cooked meat, especially pork or lamb, or touching the hands to the mouth after contact with raw or undercooked meat.
Persons with a weakened immune system are at risk for developing a severe case of toxo. At high risk therefore for severe toxo are:
Children and adults with an inherited immune defect, a
Anyone with AIDS,
Anyone receiving systemic (bodywide) chemotherapy,
Anyone who has received a transplant and is on immunosuppressive therapy (to prevent rejection of their transplant), and
The fetus and newborn.
Toxoplasma gondii is a well-known teratogen -- an agent that can cause birth defects. If a woman is pregnant when she is infected, the parasite can cross the placenta from her to the baby with sometimes catastrophic consequences.
Children born with toxo (congenital toxoplasmosis) can have mental retardation, convulsions (epilepsy), spasticity, cerebral palsy, and partial or complete deafness and blindness.
- transduction: : the action or process of converting something and especially energy or a message into another form
2 : the transfer of genetic material from one organism (as a bacterium) to another by a genetic vector and especially a bacteriophage -- compare TRANSFORMATION 2
- transfecting: Infection of a cell with isolated viral nucleic acid followed by production of the complete virus in the cell; also : the incorporation of exogenous DNA into a cell.
- Transfer Factor: A substance that is produced and secreted by a lymphocyte functioning in cell-mediated immunity and that upon incorporation into a lymphocyte which has not been sensitized confers on it the same immunological specificity as the sensitized cell. Also, a trademarked substance, alleged to "boost" the human autoimmune response.
- transparietal: Through or across a wall, as through the intact body wall.
- transsphenoidal: Operative method of reaching the pituitary gland or skull base traversing the nose and sinuses.
- transsphenoidal approach: See transsphenoidal
- transventricular: Passing through or performed by way of a ventricle.
- trapezious: Trapezius. A large flat triangular superficial muscle of each side of the upper back that arises from the occipital bone, the ligamentum nuchae, and the spinous processes of the last cervical and all the thoracic vertebrae, is inserted into the outer part of the clavicle, the acromion, and the spine of the scapula, and serves chiefly to rotate the scapula so as to present the glenoid cavity upward.
- trapezius: large flat triangular superficial muscle of each side of the upper back that arises from the occipital bone, the ligamentum nuchae, and the spinous processes of the last cervical and all the thoracic vertebrae, is inserted into the outer part of the clavicle, the acromion, and the spine of the scapula, and serves chiefly to rotate the scapula so as to present the glenoid cavity upward
- Treacher Collins syndrome: (noun)
: MANDIBULOFACIAL DYSOSTOSIS
Collins, Edward Treacher (1862-1932),
- tremors: a trembling or shaking usually from physical weakness, emotional stress, or disease
- trials: An experiment to see if a treatment works. Click here for details
- trigeminal: trigeminal nerve
: either of the fifth pair of cranial nerves that are mixed nerves and in humans are the largest of the cranial nerves and that arise by a small motor and a larger sensory root which both emerge from the side of the pons with the sensory root bearing the trigeminal ganglion and dividing into ophthalmic, maxillary, and mandibular nerves and the motor root supplying fibers to the mandibular nerve and through this to the muscles of mastication --called also fifth cranial nerve, trifacial nerve, trigeminus
- Trigeminal Nerve: Either of the fifth pair of cranial nerves that are mixed nerves and in humans are the largest of the cranial nerves and that arise by a small motor root and a larger sensory root which both emerge from the side of the pons with the sensory root bearing the trigeminal ganglion and dividing into ophthalmic, maxillary, and mandibular nerves and the motor root supplying fibers to the mandibular nerve and through this to the muscles of mastication -- called also fifth cranial nerve, trifacial nerve, trigeminus.
- trigeminal neuralgia: (noun)
: an intense paroxysmal neuralgia involving one or more branches of the trigeminal nerve -- called also tic douloureux
- trigeminal neuroma: A tumor in the fifth cranial nerve.
- trigeminal tumors: Trigeminal. Of, pertaining to, or designating, the fifth pair of cranial nerves, which divide on each side of the head into three main branches distributed to the orbits, jaws, and parts of the mouth; trifacial.
- trigone: a triangular body part ; specifically : a smooth triangular area on the inner surface of the bladder limited by the apertures of the ureters and urethra
- trimigneal neauralgia: See trigeminal neuralgia.
- trisomy: The condition (as in Down's syndrome) of having one or a few chromosomes triploid in an otherwise diploid set.
- trochlear: Of, near, or relating to either of the fourth pair of cranial nerves that arise from the dorsal aspect of the brain stem just below the inferior colliculus and supply the superior oblique muscle of the eye with motor fibers
- Trochlear nerve: The trochlear nerve (the fourth cranial nerve or IV) is a motor nerve that innervates a single muscle: the superior oblique muscle of the eye. The trochlear nerve emerges from the dorsal aspect of the brainstem at the level of the caudal mesencephalon, just below the inferior colliculus. It circles anteriorly around the brainstem and runs forward toward the eye in the subarachnoid space. It passes between the posterior cerebral artery and the superior cerebellar artery, and then pierces the dura just under the free margin of the tentorium cerebelli, close to the crossing of the attached margin of the tentorium and within millimeters of the posterior clinoid process. It enters the cavernous sinus, where it is joined by the other two extraocular nerves (III and VI), the internal carotid artery, and portions of the trigeminal nerve (V). Finally, it enters the orbit through the superior orbital fissure and innervates the superior oblique muscle. The superior oblique muscle ends in a tendon that passes through a fibrous loop, the trochlea, located anteriorly on the medial aspect of the orbit. Trochlea means “pulley” in Latin; the fourth nerve is named after this structure.
The trochlear nerve is unique among the cranial nerves in several respects. It is the smallest nerve in terms of the number of axons it contains. It has the greatest intracranial length. Along with the optic nerve (cranial nerve II), it is the only cranial nerve that decussates (crosses to the other side) before innervating its target. Finally, it is the only cranial nerve that exits from the dorsal aspect of the brainstem.
Injury to the trochlear nerve cause weakness of downward eye movement with consequent vertical diplopia (double vision). The affected eye drifts upward relative to the normal eye, due to the unopposed actions of the remaining extraocular muscles. The patient sees two visual fields (one from each eye), separated vertically. To compensate for this, patients learn to tilt the head forward (tuck the chin in) in order to bring the fields back together – to fuse the two images into a single visual field. This accounts for the “dejected” appearance of patients with IV nerve palsies.
As would be expected, the diplopia gets worse when the affected eye looks toward the nose because the contribution of the superior oblique muscle to downward gaze is greater in this position. Common activities requiring this type of convergent gaze are reading the newspaper and walking down stairs. Diplopia associated with these activities may be the initial symptom of a fourth nerve palsy.
Trochlear nerve palsy also affects torsion (rotation of the eyeball in the plane of the face). Torsion is a normal response to tilting the head sideways. The eyes automatically rotate in an equal and opposite direction, so that the orientation of the environment remains unchanged – vertical things remain vertical.
Weakness of intorsion results in torsional diplopia, in which two different visual fields, tilted with respect to each other, are seen at the same time. To compensate for this, patients with trochlear nerve palsies tilt their heads to the opposite side, in order to fuse the two images into a single visual field.
The characteristic appearance of patients with fourth nerve palsies (head tilted to one side, chin tucked in) suggests the diagnosis, but other causes must be ruled out. For example, torticollis can produce a similar appearance.
- tuberous sclerosis: An inherited disorder of the skin and nervous system that is characterized typically by epilepsy and mental retardation, by a rash of the face resembling acne, and by multiple noncancerous tumors of the brain, kidney, retina, and heart and that is controlled by an autosomal dominant gene maintained in human populations by a high mutation rate -- called also epiloia.
- tumor: 1. Swelling, one of the cardinal signs of inflammation; morbid enlargement. 2. A new growth of tissue in which the multiplication of cells is uncontrolled and progressive. Also called neoplasm.
- tumor calcification: Calcification. The process by which organic tissue becomes hardened by a deposit of calcium salts within its substance.
- tumor calcium: See calcification.
- tumor cerebral calcificado: See: calcification.
- tumor cerebri: See: pseudotumor cerebri
- tumor in brain stem: See: brain stem.
- tumor on cerebral cortex: See: cerebral cortex.
- typical brain stem glioma: A brain stem glioma that infiltrates diffusely throughout the pons (the middle portion of the brain stem), sometimes spreading to the midbrain (the upper portion of the brain stem) or he medulla (the bottom portion of the brain stem). The term diffuse intrinsic pontine glioma is synonymous. By pathology, this tumor is most often a fibrillary astrocytoma or its higher grade counterparts (anaplastic astrocytoma and glioblastoma multiforme).
- tyramine: An amino acid found in certain foods that can cause adverse reactions when consumed while receiving certain chemotherapy treatments. These foods include but are not limited to red wine, cheese, smoked fish, chicken livers and figs. Tyramine is also associated with migraine headaches.