Hemorrhage causes 15% of strokes and occurs in several forms, including epidural hemorrhage (traumatic, often involves middle meningeal artery in dura, can cause subfaldne or other cerebral herniation, "talk and die syndrome"), subdural hemorrhage (traumatic, rupture of bridging veins, risk factors of cerebral atrophy and abnormal hemostasis, various neurologic symptoms, often recurs), subarachnoid hemorrhage (ruptured berry aneurysm or other causes, "thunderclap" headache, nuchal rigidity, neurologic deficits, stupor), and intracerebral hemorrhage (hypertension, vascular malformation, or less commonly, many other predisposing conditions: basal ganglia, cerebellum, pons, or centrum ovale, severe headache with rapid progression of symptoms, often to coma).
Berry aneurysms of the Circle of Willis (risk factors include hypertension, cigarette smoking, Marfan syndrome, Ehlers-Danlos type 4, and adult polycystic kidney disease) are the most frequent cause of subarachnoid hemorrhage (1/3 die, 1/3 recover, and 1/3 re-bleed with risk of death).
CNS trauma to the cranial cavity and brain can take several forms, including concussion (transient loss of consciousness after impact against a rigid surface), contusions (brain bruises, sometimes in a coup and contrecoup pattern, can cause local infarction), and diffuse axonal injury (sudden acceleration/deceleration stretches and "pops" axons, producing little gross injury, but coma from which recovery often never occurs). CNS trauma to the spinal cord is usually due to vertebral displacement, and can cause paraplegia (thoracic segments or below), tetraplegia (cervical segments), and paralysis of the diaphragm (above C4).
Cerebral herniations can take several forms, including subfalcine (cingulate gyrus goes under falx and can compress the anterior cerebral artery), transtentorial (temporal lobe uncus goes under the tentonum, can compress the third nerve, and cause Duret hemorrhage in brainstem), and cerebellar tonsillar (goes through the foramen magnum to compress the medulla causing cardiorespiratory arrest).
Neural tube defects (risk factor: folate deficiency) are the most common developmental CNS abnormalities and can take several forms, including anencephaly (no cranial vault, death in infancy), spina bifida occulta (bony defect of the vertebral arch), meningocele (bony defect with outpouching of meninges), meningomyelocele (with outpouching meninges, spinal cord, and spinal roots), and myelocele (complete exposure of spinal cord). Paraplegia and urinary incontinence may complicate the more severe spinal cord defects.
Amold-Chiari malformation Type I (common, often asymptomatic) is a downward displacement of the cerebellar tonsils. Type 2 (often symptomatic) has a small posterior fossa, downward displacement of cerebellar vermis and medulla, compressed fourth ventricle with obstructive hydrocephalus, and frequent lumbar meningomyelocele and syringomyelia (CSF-filled channel near central canal; most often related to Amold-Chiari type 2).
Perinatal brain injury (risk factor prematurity) can cause cerebral palsy, germinal matrix hemorrhage, periventricular leukomalacia, and multicystic encephalopathy. ;
Multiple sclerosis is a chronic relapsing-remitting disorder of probable autoimmune origin characterized by recurrent episodes of demyelination (causing "plaques") and defective remyelination in the brain (including optic nerves) and spinal cord, which results in progressive (but variable in time and from person to person) neurological deficits (visual changes, sensation changes, motor changes, neuropsychiatry disturbances). Central pontine myelinosis is a rare, potentially fatal, focal demyelination of the basis pontis possibly related to over-rapid correction of hyponatremia in malnourished patients and alcoholics.
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