Extracranial aneurysms of the posterior inferior cerebellar artery. Literature review and report of a new case.

Aneurysms arising from the extracranial portion of the posterior-inferior cerebellar artery (PICA) are considered extremely rare. To date, only ten cases have been reported in the literature. The authors report a case of a 29 year-old male patient admitted comatose in Hunt-Hess grade IV because of an subarachnoid haemorrhage predominantly involving the left cranio-vertebral junction up to C2 rather than the posterior fossa and the fourth ventricle. Angiography showed an extracranial aneurysm at left vertebral artery-PICA junction a few millimetres superior to the dural entry point of the vertebral artery (VA). A left extreme-lateral approach was performed and the aneurysm was successfully clipped. On first year follow-up the patient had completely recovered with no neurological deficits. This paper analyzes the literature review about these rare aneurysms and the technical notes regarding the cranio-vertebral junction approach to these lesions. Factors affecting the neurological outcome of these aneurysms are also reported.