title: Aneurysm at the posterior inferior cerebellar artery of extradural origin for preoperative evaluation of safe clipping: case report and review of the literature.
abstract: BACKGROUND
  As far as we know, 6 cases of extracranial (including craniocervical junction) intradural aneurysms of the posterior inferior cerebellar artery have been previously reported. However, preoperative detailed evaluation of the origin site and a course of the posterior inferior cerebellar artery by means of angiography were not reported in previous papers.
  
  
  METHODS
  We report a rare case of aneurysm of the posterior inferior cerebellar artery, which originated extradurally from the right vertebral artery. A 69-year-old woman experienced a sudden headache 16 years ago and a computed tomography scan showed a subarachnoid hemorrhage around the midbrain. Four-vessel cerebral angiography, however, failed to disclose a source of the hemorrhage. Magnetic resonance angiography incidentally revealed an aneurysm at the craniocervical junction 16 years after the subarachnoid hemorrhage. The aneurysm was exposed and clipped via a suboccipital route. At surgery, it was of no use to apply a temporary clip on the intradural segment of the vertebral artery, because the posterior inferior cerebellar artery was found to enter the intradural space separately from the vertebral artery. The blood flow to such an aneurysm cannot be stopped with this procedure.
  
  
  CONCLUSIONS
  Careful neuroimaging study is essential for the accurate diagnosis and successful treatment of such a rare aneurysm.
mesh_terms: D000368:Aged; D002531:Cerebellum / Q000098:blood supply*; D002533:Cerebral Angiography; D005260:Female; D006801:Humans; D002532:Intracranial Aneurysm / Q000473:pathology / Q000601:surgery*; D020769:Posterior Cerebral Artery / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D016896:Treatment Outcome