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Overview of the collateral circulation of the brain
| Structural classification | Functional classification |
|---|---|
| • Circle of Willis | • Primary |
| • Microvascular intracranial collaterals | • Secondary |
| - Leptomeningeal (pial) collaterals | • Tertiary |
| - Subcortical collaterals | |
| • Extracranial sources of collateral circulation |
