Isolated posterior spinal artery aneurysm.

Isolated aneurysms of the posterior spinal artery (not associated with arteriovenous malformations) are exceptionally rare. Three cases have been reported in the literature to date. We report a case of an isolated posterior spinal artery aneurysm causing acute subarachnoidal haemorrhage. Spinal artery aneurysms are contrasted with the more common intracranial aneurysms in terms of presentation and pathogenesis.