CNS pathology Flashcards
What are the two global causes of cerebrovascular disease?
ischemia and hemorrhage
What are the major etiologies of global cerebral ischemia?
low perfusion (e.g. atherosclerosis) acute decrease in blood flow (e.g. shock) chronic hypoxia (e.g. anemia) repeated episodes of hypoglycemia (e.g. insulinoma)
What are the outcomes of mild global ischemia? moderate global ischemia? severe global ischemia?
mild - transient confusion with prompt recovery moderate - infarcts to watershed areas and damage to exquisitely sensitive neurons (layers 3,5 and 6 of the cerebral cortex, hippocampus and purkinje layer of the cerebellum) severe - death or vegetative state
What is the difference between an ischemic stroke and a transient ischemia attack?
TIA = symptoms for < 24 hours IS = symptoms for < 24 hours
What are the three types of ischemic strokes? What is the cause of each? What type of infarct does each type lead to?
Thrombotic stroke - rupture of an atherosclerotic plaque causes thrombus formation that blocks the artery to the brain. Results in a pale infarct at the periphery of the cortex embolic stroke - thromboembolus travels to the arteries of the brain and gets lodged. Eventually the body lyses the clot and blood flows again, resulting in a hemorrhagic infarct at the periphery of the cortex lacunar stroke - hyaline arteriolosclerosis blocks lenticulostriate arteries resulting in small cystic areas of infarction that look like lakes.
What type of necrosis occurs in ischemic strokes? What are the histological changes that occur after necrosis?
liquidative necrosis 12-24 hours after infarction - neurons turn red (eosinophilic change) 1 day after infarction - neutrophil infiltration, then microglial infiltration 2 weeks after infarction - gliosis (glial scar formation) Results in a fluid filled cystic space surrounded by glial scar
What is the cause of an intracerebral hemorrhage? What is the most common site? How does it present?
rupture of Charcot-Bouchard micro aneurysms of the lenticulostriate vessels. Basal ganglia is the most common site Presents with severe headache, nausea, vomiting and eventual coma
What is the cause of a subarachnoid hemorrhage? How does it present? What are the characteristics of the lumbar puncture?
Most commonly due to rupture of a berry aneurysm but also AV malformations and an anticoagulated state Presents as a sudden, very severe headache with nuchal rigidity LP shows xanthochromia (yellow hue due to bilirubin breakdown from RBC lysis)
What is the difference on CT between a epidural and subdural hematoma? How does their presentation differ?
Epidural - lens-shaped lesion on CT that do not cross suture lines Subdural - crescent-shaped lesion on CT that can cross suture lines Epidural - lucid interval then sudden onset of neurological symptoms Subdural - slow, progressive neurological symptoms
What are three types of herniation? What portions of the brain are herniating in each type? What are the complications of each type?
Tonsillar herniation - displacement of the cerebellar tonsils through the foramen magnum. Complications include compression of the brainstem (cardiopulmonary arrest)
subfalcine herniation - displacement of the cingulate gyrus under the falx cerebriComplications include compression of the anterior cerebral artery (infarction)
uncal herniation - displacement of the temporal lobe uncus under the tentorium cerebelli. Complications include compression of CN III (dilated pupil and eye looking down and out), compression of posterior cerebral artery (infarction) and rupture of the paramedian artery (brainstem hemorrhage)
What are the types of demyelinating disorders?
Leukodystrophies, multiple sclerosis, subacute sclerosing panencephalitis, progressive multifocal leukoencephalopathy, central pontine myelinolysis
What is the pathogenesis of the leukodystrophies? What are the common subtypes of leukodystrophies? What is the mechanism of disease for each subtype?
Leukodystrophies are all characterized by inherited mutations in enzymes necessary for the production or maintenance of myelin which lead to degeneration of white matter in the brain
Metachromatic leukodystrophy - deficiency in arylsulfatase leads to accumulation of sulfatides in the lysosomes of oligodendrocytes
Krabbe disease - deficiency of galactocerebrosidase leads to accumulation of galactocerebroside in macrophages
Adrenoleukodystrophy - defective enzyme that adds CoA to long chain fatty acids. Fatty acids accumulate and destroy the adrenal gland and the white matter
How are myelin/oligodendrocytes destroyed in MS? What are the clinical features of MS? What are the diagnostic tests for MS?
Myelin and oligodendrocytes are destroyed by an autoimmune proess in MS.
Clinical features depend on where the lesion is:
optic nerve - blurred vision in one eye
brainstem - vertigo and scanning speech that mimics alcohol intoxication
medial longitudinal fasciculus - internuclear opthalmoplegia
cerebral white matter - hemiparesis or unilateral loss of sensation
spinal cord - lower extremity loss of sensation or weakness
ANS - bowel, bladder and sexual dysfunction
Diagnosis by MRI (plaques of white matter demylination) and LP (increased lymphocytes, increased IgGs and myelin basic protein)
What is the pathogenesis of subacute sclerosisng panencephalitis?
slowly progressing, persistant infection of the brain by the measles virus
What is the pathogenesis of progressive multifocal leukoencephalopathy?
Infection of the oligodendrocytes by the JC virus.
