Dissecting aneurysms limited to the basilar artery: report of two cases and review of the literature.

Spontaneous dissecting aneurysms limited to the basilar artery are rare. We describe two patients who presented to our institution with different clinical problems, one with brain stem infarction and the other with subarachnoid hemorrhage. We describe the clinical and imaging features in these patients, their treatment, and outcome. We also reviewed the literature concerning this entity, and we have identified 32 patients (including our two patients) with angiographically confirmed dissecting aneurysms limited to the basilar artery. Of these, 40.6% presented with brain stem infarction, 50.0% presented with subarachnoid hemorrhage, and 9.4% presented with both infarction and subarachnoid hemorrhage. Patients who presented with basilar artery dissecting aneurysms and brain stem infarction tended to be younger (mean age, 38 +/- 7 years) than those who presented with subarachnoid hemorrhage (48 +/- 12 years) and were more likely to be male. We discuss the natural history of this entity and suggest an approach to clinical management for these patients.