Extracranial aneurysm of the posterior inferior cerebellar artery with an aberrant origination: case report.

Aneurysms of the extracranially originating posterior inferior cerebellar artery are very rare. An anatomic insight of its possible course and variations is necessary when confronting such extraordinary lesions.A 19-year-old man presented with the sudden onset of severe headaches. A physical examination was positive only for neck rigidity. Computed tomographic scans of the brain depicted intraventricular hemorrhage. TECHNIQUE AND INTERVENTION: Four-vessel brain digital subtraction angiography revealed an extracranial posterior inferior cerebellar artery arising extradurally from the right vertebral artery between the C1 and C2 vertebrae, bearing a saccular aneurysm in an upper cervical intradural location. An anterior inferior cerebellar artery-posterior inferior cerebellar artery variant was also found on the left side. Computed tomographic angiography failed to unmask the lesion. The aneurysm was clipped through a suboccipital craniectomy and C1 laminectomy.The patient did well after surgery and was discharged from the hospital without neurological deficit. One can conclude that a comprehensive diagnostic approach oriented to the patient history and clinical data is mandatory to preclude such lesions evading the vigilant surgeon.