Term
| what are the 3 extra chromosome anomalies? |
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Definition
| trisomy 13-15 (patau syndrome), trisomy 18 (edward syndrome), and trisomy 21 (down's syndrome) |
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Term
| what characterizes trisomy 13-15 (patau syndrome)? |
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Definition
| underdeveloped limbic lobe and cerebellar vermis. usually die by 6 mos. |
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Term
| what characterizes trisomy 18 (edward syndrome)? |
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Definition
| microcephaly and abnormal development of neurons in the white matter cortex of the cerebellum (cells that are supposed to migrate and make the granular and golgi layers are not doing it). usually die by 1 yr. |
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Term
| what characterizes trisomy 21 (down's syndrome)? |
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Definition
| small cerebellum, less folding of gyri, fewer neuronal synapses. these pts can reach adulthood and reproduce but age more rapidly. |
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Term
| what is the cat cry syndrome? |
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Definition
| missing part of chr 5 (rare). pts w/this make noises like a cat, have an underdeveloped cerebellum, are microcephalic, and atrophy of the phonetic center of the brain (cat noises). these pts can reach their teens. |
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Term
| what are the 2 dominant gene anomalies? |
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Definition
| neurofibromatosis and tuberous sclerosis |
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Term
| what is neurofibromatosis? |
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Definition
| "elephant man", often normal at birth, these pts have tumor formation (large nodules) which begin in the fibrous connective tissue capsule of the neural receptors in the PNS which progress centrally along the nerves and may reach the viscera and brain. these tumors may become malignant. (dominant gene anomaly) |
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Term
| what is tuberous sclerosis? |
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Definition
| this may produce a triad of symptoms: 1) discolored skin lesions involving the sebaceous glands. 2) calcifications in the brain. 3) seizures. if only 1 symptom presents, pts will probably be fine, if all 3 - poor prognosis. (dominant gene anomaly) |
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Term
| what are the recessive gene anomalies? |
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Definition
| phenylketonuria and sex-linked recessive gene |
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Term
| what is phenylketonuria? tx? |
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Definition
| phenylalanine hydroxylase cannot convert phenylalanine to tyrosine. build-up of phenylalanine and its breakdown products phenylpyruvic acid and phenylacetic acid then causes mental retardation. tx: put on low phenylalanine diet. |
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Term
| what is sex-linked recessive gene? |
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Definition
| this usually involves forked stenosis of the aqueduct of sylvius (cerebral aqueduct) and causes hydrocephalus. however, only 2% of hydrocephalus can actually be genetically linked. |
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Term
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Definition
| an increase in CSF and a symptom (not disease) of many possible causes (tumors, aneurysms, etc). it is not synonymous w/increased cranial size - after 2 years, the skull is set and further CSF increases will just crush the brain instead of expanding the skull. |
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Term
| how is hydrocephalus treated? |
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Definition
| a shunt is run from the brain to the abdominal cavity, which absorbs the CSF |
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Term
| what effects the prognosis for hydrocephalus? |
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Definition
| the cerebral hemisphere is 4 mm thick. hydrocephalus which expands the brain to the point where the cerebral hemisphere is 2 mm thick = pt's brain can return to normal size w/o damage. if the increase in pressure causes the cerebral hemisphere to 1 mm = major nerve damage. (wall thickness of 1-2 cms has a variable outcome) |
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Term
| what are the 2 main causes of hydrocephalus? |
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Definition
| increasing the CSF production (tumor in choroid plexus) or blocking the flow pattern (more common) |
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Term
| what are the classifications of hydrocephalus? |
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Definition
| communicating (only partial blockage, slow increase in pressure) and noncommunicating hydrocephalus (total blockage, rapid onset, may be fatal w/o immediate drainage) |
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Term
| what are the causes of communicating hydrocephaly? |
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Definition
| cephaloceles (reduction in CSF flow if this occurs around the cisterna magnum etc), lissencephaly (failure of gyri to form = less subarachnoid space), meningeal inflammation (+in utero damage) and arnold-chiari (obstruction of the foramina of magendie/median aperture w/herniation of the medulla and cerebellar tonsils through the foramen magnum and into the vertebral canal) |
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Term
| how does arnold-chiari affect the morphology of the brain? |
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Definition
| the hemispheres become enlarged and flatten the posterior cranial fossa. the cerebellum and brainstem can get pushed down as far as T4-7, which can and does often block the cisterna magnum (worsens CSF pressure). the brainstem can become kinked (if the pontine flexure doesn't form, the brainstem remains too long and is forced down through the foramen magnum, which then causes the cervical flexure which normally straightens out the hindbrain to become kinked). pts w/arnold-chiari are born relatively normal, but if not treated the communicating hydrocephalus can become non-communicating. **all children w/arnold chiari have spina bifida cystica (symptoms: abnormal gag reflex, cough reflex, apnea b/c of compressed medulla) and 80% will need to be shunted. |
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Term
| what are the causes of non-communicating hydrocephaly? |
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Definition
| cysts/tumor/aneurysm (in brain tissue or arachnoid), aqueductal stenosis (**most common type of anomaly leading to congenital hydrocephalus - occurs equally as forking or gliosis), and dandy-walker (failure of the foramen of magendie *and luschka* to open) |
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Term
| how does dandy-walker affect the morphology of the brain? |
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Definition
| the foramen of magendie and luschka do not open = no opening from the 4th ventricle to the subarachnoid space = non-communicating hydrocephalus. the cerebellum becomes very enlarged, the vermis does not form = pts have balance problems. most pts will die in infancy, but if there is a small hole they may live. these pts have a very big posterior fossa (opposite arnold-chiari) |
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Term
| what are the 2 outcomes if a cephalocele causes herniation through the cranium? |
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Definition
| 1) cephalic meningocele: meningeal covering of the brain herniates through the cranium. 2) encephalocele: both the meningeal coverings and brain tissue herniate through cranium. |
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Term
| what is anencephalus? what are the 2 classifications? |
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Definition
| anencephalus: the neural tube fails to close in the head region and only the base of the cranium is present - the brain lies open and exposed on the top of the base (the brain tissue is not covered by skin). 2 types = 1) exencephalus: only a small part of the brain is exposed, w/development, exencephalus will convert either to an encephalocele by becoming covered with skin or open up to become an anencephalus. 2) iniencephalus: anencephalus combined with abnormal brain flexion (brain extends back rather than flexes forward). |
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Term
| what are the 3 kinds of spina bifida? |
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Definition
| spina bifida occulta, spina bifida cystica meningocele, spina bifida cystica myelomeningocele, and spina bifida cystica hydromyelia. |
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Term
| what is spina bifida occulta? |
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Definition
| a common (~ 20% of pop) malformation where the spinous process may be missing and the vertebral canal is exposed posteriorly (spinal cord and its coverings are intact). except in people who do heavy manual labor this condition is usually asymptomatic and discovered on routine examination. |
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Term
| what is spina bifida cystica meningocele? |
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Definition
| along w/the vertebral defect mentioned in occulta, the neural arches of the affected vertebrae are missing and the meninges of the cord herniate through the defect creating a large CSF filled cyst on the back. the spinal cord itself is normal and remains inside the vertebral canal. (10% of ail cases of spina bifida cystica.) |
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Term
| what is spina bifida cystica myelomeningocele? what are the 2 types of lesions? |
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Definition
| along w/the vertebral defect mentioned in occulta, the neural arches of the affected vertebrae are missing and the meninges of the cord herniate through the defect *as well as the spinal cord - creating a CSF+spinal cord filled lesion on the back. 87% are open and are susceptible to infection. 2 kinds of lesions: 1) UMN - longitudinal descending tracts or neurons in the higher brain centers are destroyed = spastic (reflex) paraplegia of lower limbs. 2) LMN - neurons in cord itself are destroyed resulting in flaccid paraplegia. (90% of all cases of spina bifida cystica) |
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Term
| what is spina bifida cystica hydromyelia? |
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Definition
| along w/the vertebral defect mentioned in occulta, the neural arches of the affected vertebrae are missing and the meninges of the cord herniate through the defect as well as the spinal cord - *the central canal of which is enlarged, forcing just the dorsal part of the cord to herniate out and form a cyst. the build-up of CSF pressure in the central canal damages the neurons in the walls of the cord and results in sensory and motor deficits. (rare) |
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Term
| at what level does spina bifida cystica occur most often? |
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Definition
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Term
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Definition
| multiple cavities in the spinal cord surrounded by dense gliogenous tissue. *congenital syringomyelia occurs most often in the *cervical region and is probably caused by abnormal obliteration of the dorsal (posterior) part of the central canal (at 8-10 wks) resulting in multiple canals. as the glial cells form they fail to migrate properly and localize around the central canals where they eventually destroy the ependymal lining of the central canals and form tumors. the multiple canals (cavities) and associated gliosis disrupts the nerve tracts crossing (ventral white commissure) close to the central canal which causes loss of pain and temperature sensation, muscle weakness and muscle atrophy. **in adults, syringomyelia may occur secondary to infection**. |
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Term
| what characterizes double spinal cord anomalies? what are the 2 kinds? |
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Definition
| symptoms include difficulty learning to walk and abnormal gait. 1) diplomyelia: the cords are completely separate with their own nerve roots and ganglia and their own dural coverings. 2) diastematomyelia - two partially or completely separated cords within a common dural sheath *often with a fibrocartilaginous spur separating the two parts. usually the two cords *share nerve roots and ganglia. |
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Term
| how do you determine at what spinal level damage has occurred? |
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Definition
ex: run needle down the leg, get a weak eversion and no inversion of the toes. if there is no eversion, L5 has
to be out and since inversion is weak, L4 is probably working. (motor diagrams should be provided) |
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