Cerebrovascular diseases Flashcards
List the mechanisms by which hypoxia (deprivation of O2) can occur by
low level of oxygen in blood
low blood flow to tissue-ischemia
oxygen utilization by tissue is impaired
What is the definition of ischemia?
low blood flow
When does global ischemia to the brain occur?
systolic BP <50
When does focal ischemia in the brain occur?
during obstruction of local blood supply, leads to infarction
What area of the brain does global ischemia impact first?
borderzone/watershed areas
low flow areas between anterior, middle and posterior cerebral arteries
List the cell types in decreasing order of oxygen deprivation sensitivity
neurons, oligodendrocytes, astrocytes
List the brain regions in decreasing order of oxygen deprivation sensitivity
hippocampus (CA1 sector-sommer sector)
Lamina 3 & 5 of cerebral cortex (laminar necrosis)
purkinje cells in cerebellum
What role does glutamate play during ischemic/hypoxic injury?
when present in excess is neurotoxic, is commonly present in excess during ischemic/hypoxic injury
What determines the selective vulnerability of different cells/regions?
variable O2/energy requirements of different neurons and neuronal populations
What histologic changes occur to acutely hypoxic/ischemic neurons?
“red is dead”
pyknotic cells with shrunken and dark nucleus, no nucleolus visible
red cytoplas w/ no missl substance visible
What are the outcomes of severe global ischemia?
widespread neuronal death, irrespective or regional vulnerability
leads to persistent vegetative states and/or brain death
How is brain death defined?
diffuse cortical injury with brainstem injury (absent reflexes and respiratory drive)
What are the findings of severe global ischemia (respirator brain) on autopsy?
swollen brain, slit like ventricles, herniation
collapsed vessels due to swelling
What are the 3 major causes of focal ischemia?
thrombosis (atherosclerosis)
emobli
lacunar infarcts/slit hemorrhages
Where does thrombosis/atherosclerosis most commonly cause focal ischemia?
carotid bifurcation
origin of MCA
origin or end of basilar artery
What type of infarct do emboli commonly cause?
hemorrhagic infarct
What are cardiac sources of emboli?
mural thrombi
endocarditis (bacterial or marantic emboli)
What are non cardiac sources of emoli?
atheromas
fat, neoplasms, air
Which vessel is most commonly affected by emboli?
MCA
What causes lacunar infarcts/slit hemorrhages?
hyaline arteriolosclerosis caused by hypertension and diabetes mellitus
What are lacunes?
small stroked in subcortical brain structures that may be hemorrhagic
What are uncommon causes of brain infarction?
vasculitis arterial dissection of carotid arteries coagulation disorders microvasculopathy amyloid angiopathy drug abuse
What are the characteristics of primary angiitis (vasculitis) of the CNS?
involves multiple small/medium sized meningeal and parenchymal vessels
chronic inflammation, fibrinoid necrosis, multinucleated giant cells, wall destruction
What does acute infarct look like on gross examination?
soft, swollen, grey-white distinction blurred
up to 48 hrs post infarct
What does subacute infarction look like on gross examination?
liquefactive necrosis
2-3 wk post infarct
What does chronic infarction look like on gross examination?
cavitated, all dead tissue removed
several months post infarct
What does acute infarct look like on microscopic exam?
red neurons, pallor
possibly neutrophils
What does subacute (organizing) infarct look like on microscopic exam?
macrophages, necrotic tissue, reactive astrocytes, vascular proliferation
What does chronic infarct look like on microscopic exam?
cavilty with glial scar
What are the signs and symptoms of vascular dementia?
pattern of damage
samll areas of infarct/multiple lacunar infarcts
diffuse white matter disease
infarct occur in areas important for cognition/memory
What does cerebral venous thrombosis cause? Where?
hemorrhagic infarcts
superior sagital and/or lateral sinuses (results in parasagitall hemorrhagic infacts)
What are some causes of central venous thrombosis?
infection, injury, neoplasm, surgery, pregnancy OCPs, hematologic abnormalities, dehydration, malignancy
What are causes of intracerebral hemorrhage?
hypertension (MCC)
vascular malformations
amyloid angiopathy
What are key features of HTN induced ICH?
abrupt onset of severe neurologic dysfunction when hematoma is large
putamen, thalamus, pons, cerebellum commonly affected
hyaline arteriolosclerosis
What is the most common type of vascular malformation?
arteriovenous malformation: tangled network of vessels with AV shunt
What are other, less common types of vascular malformations?
capillary telangiectasia
cavernous angioma
venous angioma
What are causes of lobar hemorrhage?
neoplasms drug abuse vasculitis hemorrhagic diathesis amyloid angiopathy
What are common causes of subarachnoid hemorrhage?
trauma
aneurisms
What are 3 common types of CNS aneurisms
saccular (berry)
mycotic (fungus)
fusiform/atherosclerotic
What are key features of saccular/berry aneurism?
“the worst head ache i’ve ever had” (w/rupture)
increased risk w/ HTN, smoking, AVM, etc
increased risk of rupture as size increases
not present at birth, but hte defect in the media is congenital and the aneurism develops over time
usually occurs at branch points in the anterior circulation (ant communicating and anterior cerebral junction most common location)
What is a stroke?
a sudden failure of brain function due to diminished blood flow to a part of the brain, or due to bleeding inside the brain
What are 5 major signs of a stroke?
hemineglect vision loss loss of speech or comprehension numbness on one side weakness on one side
What does complete lack of blood flow result in?
cortical laminar necrosis
What does low blood flow result in?
watershed injury
What causes arteriovenous malformations?
atherosclerosis
congenital
prone to develop in cocain users
more common in HTN patients
