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Illustration of a posterior inferior cerebellar artery (PICA) with extradural C2-origin. A muscular branch may arise from the extradural segment of the artery. An intradural small anastomotic branch between the vertebral artery and PICA is sometimes found. Extracranial aneurysms may arise proximally at the level of dural penetration (1) or distally on the ascending vertical segment (2). Aneurysms may also develop on the intracranial PICA (3).
