ADD-ONS / ANATOMY

Collateral cerebral circulation

Created 01/03/2022, last revision 18/05/2023

collateral cerebral circulation refers to the network of vascular channels that stabilize cerebral blood flow if the main vessel is stenosed or occluded
- arterial insufficiency may be caused by thromboembolism, hemodynamic compromise, or a combination of these factors
- reduced anterograde flow changes pressure gradients, and this leads to the opening of the collaterals
the quality of the collateral circulation significantly influences the severity and extent of cerebral infarction
- well-developed and functional collaterals can temporarily replace the function of the occluded artery, and thus considerably improve the patient’s prognosis

Classification

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intracranially, the basal arteries are interconnected to form the arterial circle of Willis
it is a heptagon consisting of the following:
- left and right ICA
- left and right A1 segments connected by an unpaired AComA
- left and right P1 segments
- left and right PComA (connecting ICA and P1 segment on each side)
  - PCOM originates at the anterior perforating substance and runs back through the interpeduncular cistern
- basilar artery tip
branches of the circle of Willis also supply the optic chiasm and tracts, infundibulum, hypothalamus, and other structures at the base of the brain
- medial lenticulostriate arteries (segment A1)
- perforating branches (from the AComA)
- thalamoperforating and thalamogeniculate arteries (from the basilar tip, proximal PCA, and PComA)
the circle of Willis allows redirection of the blood flow between both sides of the brain and between the vertebrobasilar and the internal carotid artery systems

LMAs are pial arteries that connect branches of two major cerebral arteries supplying two distinct cortical territories
these are most commonly end-to-end anastomoses between the ACA-MCA, ACA-PCA, and MCA-PCA; there are also anastomoses between both ACAs
occlusion of a cerebral artery leads to hypoperfusion in the corresponding vascular territory, creating a pressure gradient between the vessels of the unaffected area and the territory of the stenotic/occluded artery, resulting in the retrograde filling of the affected area