Cerebrovascular Disease - Cochran & Helms Flashcards
Review of anatomy
Where along the motor and sensory cortices correspond to the face, and lower limb?
What arteries supply these regions?
The lower limb is represented near the midline, within the central fissure. It is supplied by the ACA.
The face is represented laterally, near the sylvian fissure. It is supplied by the MCA.
Review of anatomy
What two vessels are the source of the brain’s blood supply?
From what do they arise, and how do they enter the cranium?
Vertebral artery arises from the subclavian artery, travels within the foramina transversaria and enters via the foramen magnum.
Internal carotid artery arises from the common carotid artery, enters via the carotid foramen.
Review of anatomy
What arteries comprise the circle of willis?
What arteries comprise the vertebrobasilar system?
Circle of willis: ACAs, Anterior communicating artery, MCAs, Posterior communicating arteries, PCAs. Gives off perforating branches.
Vertebrobasilar system: Vertebral arteries, PICAs, AICAs, basilar artery, SCAs, PCAs, pontine/labyrinthine/other smaller vessels.
Review of anatomy
What artery supplies the bulk of the neocortex?
What perforting branches does it also contribute?
The middle cerebral artery (MCA).
Gives off lenticulostriate arteries (supply the basal ganglia, internal capsule, etc).
Review of anatomy
What 5-6 components comprise the basal ganglia?
What tracts cross over at the pyramidal decussation?
Putamen, Caudate, Globus pallidus interna & externa, subthalamic region, and substantia nigra.
The pyramidal tracts (Corticobulbar, lateral and ventral corticospial). Distinguish from extrapyramidals (rubrospinal, reticulospinals, vestibulspinals, tectospinal)
Review of anatomy
Where does the Great vein (of Galen) drain to?
Trace the path of blood as it is drained from the anterior/superior frontal lobe.
Great vein drains posteriorly into the straight sinus.
Blood enters the superior sagittal sinus, travels posteriorly where it joins with the straight sinus. It travels along either transverse sinus into the sigmoid sinus, where it finally drains into the jugular vein.
Review the three mechanisms of hypoxia and give examples of each.
Which is worse - Ischemia or hypoxia? Why?
Low oxygen content of blood (eg respiratory arrest, drowning, anemia)
Low blood flow (eg cardiac arrest, obstruction, increased ICP)
Decreased oxygen utilization (eg metabolic poisons)
Ischemia is worse–the anoxia is compounded by accumulation of toxic metabolites.
What are the two forms of ischemia that affect the brain?
Give example etiologies for each.
Global ischemia (SBP < 50); due to cardiac arrest, shock, hypotension.
Focal ischemia (stroke); due to thrombosis, embolism, stenosis.
What are watershed regions?
What implication does this have in the context of cerebrovascular disease?
Watershed regions lie at the boundaries between two arterial beds.
They are less susceptible to focal ischemia (eg vessel occlusion), but are more susceptible to global ischemia.
What cells are most vulnerable to ischemia in the brain?
Why?
Neurons more than glia (oligodendrocytes > astrocytes).
Metabolic demands (oxygen/energy requirements) as well as glutamate receptor densities (Glu accumulates in tissue injury, is itself excitotoxic).
What regions of the neocortex are most damage under global ischemia.
How do they appear?
Hippocampus (distinctive “jelly roll” necrosis)
Cerebral cortex laminae 3/5/6 (laminar necrosis)
Purkinje cells of the cerebellum (???)
In severe global ischemia, brain function may be impaired to the point of persistent vegetative state or brain death.
Distinguish between the two.
PVS: Unconscious, but with preservation of sleep-wake cycles and some reflexes.
Brain death: Absent reflexes/responses and respiratory drive. Usually occurs with brainstem injury. A legal definition.
Describe the gross and microscopic appearance of brain tissue in the context of global ischemia.
Gross: Diffuse swelling, which may obliterate ventricles or cause herniation.
Microscopic: Pallor and vacuolation with eosinophilic, pyknotic neurons without apparent nucleoli or nissl substance.
Focal ischemia results from either thrombotic or embolic action. Which is more common?
What sites are most classically affected by thrombosis? Why do you think this is?
Embolic.
Branch points such as the carotid bifurcation, origin of the MCA, and the basilar artery. These sites have more turbulent flow.
Recall the pathophysiology of atherosclerosis.
If an ICA were to be completely occluded, what would be the resulting clinical presentation?
LDL deposition subintimally due to macrophage-driven oxidation causes intimal proliferation. This can “infarct” the tunica media in turn.
Complete occlusion may not have symptoms! This is due to robust collateral circulation. However, these plaques may throw small emboli.