Small vessel pathology AND cerebral blood flow

from Continuum chapter on pathophysiology

Small vessel disease- 20-30 % of total

1.lipohyalinosis is replacement of vessel wall with fibrin and collagen due to to HTN

2.microatheroma is an atheromatous plaque at the origin of a penetrating artery may cause larger subcortical strokes.

3. Fibrinoid necrosis is associated with very high BP leading to necrosis of smooth muscle cells extravasation of plasma proteins which appear as fine granular eosinophilic deposits in the connective tissue of the vessel wall.

4. Charcot-Brouchard aneurysms are areas of focal dilations in the wall that thrombose and occlude the vessel



CBF

Main factors of tissue outcome are regional CBF and duration of occlusion.

Local tissue perfusion pressure, which is main factor accounting for outcome, depends on collaterals, on arterial blood pressure, and inversely correlates with local tissue pressure, which is due partly to edema.



Thresholds:

studied in carotid clamping surgeries decades ago, reversible ischemia occurred with loss of CBF to 30-50 % of normal, and permanent with less than 30 % perfusion pressure. Higher CBF values required a longer time to infarct. EEG slows at CBF<23 flat at 15.