Clinical presentation and surgical management of dissecting posterior inferior cerebellar artery aneurysms: 2 case reports.

Intracranial dissection presenting with subarachnoid hemorrhage (SAH) most commonly involves the vertebral artery. The natural history of this lesion suggests frequent early rehemorrhage and need for urgent treatment. Isolated dissection of the posterior inferior cerebellar artery (PICA) is very rare. We present 2 cases of isolated PICA dissections presenting with SAH. Both patients were middle-aged men who presented with transient loss of consciousness, severe headache, and cranial neuropathies. Initial angiography showed dilatation and narrowing of PICA consistent with dissection and aneurysm formation. The vertebral arteries were normal and there was no other cause for the SAH. Repeat angiography 2 weeks after admission revealed significant enlargement of the aneurysmal dilation of the dissected segment of PICA in both patients. Both patients were treated operatively. One patient had clip reconstruction of the PICA with preservation of flow through the PICA. Follow-up angiography one year later showed no recurrence. The other patient underwent direct surgical trapping and resection of the dissected segment of PICA after passing balloon occlusion testing at the vertebral-PICA junction. Both patients have more than 2 years of clinical follow-up and remain well. Isolated PICA dissection seems to have a less ominous natural history compared to vertebral artery dissection. These lesions need to be followed carefully for evidence of aneurysmal enlargement. Direct surgical reconstruction of the dissected segment may be possible. Balloon occlusion testing may be very helpful in determining if the involved PICA segment can be sacrificed.