Leptomeningeal collateral circulation
The term leptomeningeal refers to the two deep layers of the meninges - the
pia materand the arachnoid mater. The leptomeningeal collateral circulation is a network of blood vessels supplying the brain that follows a diffuse course over the superficial surface of the brain.
Leptomeningeal Collateral Circulation and Cerebrovascular Accidents
middle cerebral arteryis occluded during a CVA(or stroke), there is dramatic loss of blood flow to the area of the brain supplied by this artery (the lateral surfaces of the frontal, parietal and temporal lobes, including the primary motor and sensory cortexes). [Neuroanatomy: An Illustrated Color Text. 3rd Edition. Crossman & Neary. Published by Elsevier.] The leptomeningeal collateral circulation allows a very limited degree of compensation for this. However, this mild compensatory affect is nowhere near adequate - a CVA is a very serious medical emergency.
Circle of Willis, the major arterial blood supply to the brain
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