Neurons begin suffering irreversible after what duration of anoxia?
5-6 minutes
What are some causes of global brain ischemia?
- suffocation
- poisoning
- hypotension
- cardiac arrest
Which adult brain structures are mot susceptible to ischemia?
- CA1 of hippocampus
- Purkingje Cells
- Pyramidal Neurons in layers 3, 5, and 6
What important structure is located within the ACA/MCA watershed zone?
the hippocampus
What are four significant causes of focal ischemia?
- thrombosis
- embolus
- vasculitis
- CADASIL
Where in the cerebral vasculature are thrombi most common?
- carotid bifurcation
- middle cerebral artery origin
- top and bottom of basilar arter
What are the most common sources of embolus to the brain?
- heart
- carotids
- paradoxical
- fat, tumor, air
Paradoxical emboli travel through a patent ___.
foramen ovale
Emboli are most likely to lodge in which cerebral artery?
the MCA
What is an hemorrhagic infarct?
an ischemic event gets broken up and hemorrhage follows as RBCs leak through damaged endothelial cells causing petechial hemorrhages
What gross changes can you expect following ischemia?
- 0-6 hours: nothing
- 48 hours: pale, soft, swollen
- 2-10 days: friable, demarcation
- 10-21 days: liquefaction
What microscopic changes can you expect following ischemia?
- 12-24 hours: red neurons
- 12-48 hours: neutrophils
- 48 hours - 2 weeks: macrophages, necrosis
- 1 - 4 weeks: astrocytic proliferation
- chronic: glial scar, cyst, Wallerian degeneration
Name four possible causes of cerebral edema.
- tumor
- infarct/hemorrhage
- abscess
- diffuse axonal injury
Why is subfalcine herniation problematic?
it tends to compress the ACA
Why is transtentorial herniation problematic?
- compresses CN III
- compresses PCA causing occipital lobe infarction
- causes hemorrhages in brainstem
What is CADASIL?
aka cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy, an autosomal dominant vascular dementia caused by Notch3 mutation
What causes CADASIL?
a notch3 mutation
What are the features of CADASIL?
- onset in 20s-30s with migraine with aura
- depression
- recurrent infarcts leading to cognitive decline and dementia
What histologic evidence supports CADASIL?
PAS staining of vessels in a skin biopsy
What are lacunar infarcts?
small, subcortical infarcts
The most common cause of lacunar infarcts is what?
hypertensive CV disease and the resulting arteriolar sclerosis
Hypertensive CV disease affects predominant which brain structures?
deep nuclei and white mater
What are the three most common places for lacunar infarcts?
- putamen/globus pallidus
- thalamus
- internal capsule
The most common cause of intraparenchymal hemorrhage is what?
hypertension
