A pathological study of intracranial posterior circulation dissecting aneurysms with subarachnoid hemorrhage: report of three autopsied cases and review of the literature.

Three autopsied cases of dissecting aneurysms with spontaneous subarachnoid hemorrhage of the intracranial posterior circulation are reported, and the literature is reviewed to investigate the pathological characteristics and pathogenesis of this lesion. The location and pathological features of the aneurysms were different in each of the cases presented. Subadventitial hemorrhage associated with the subarachnoid hemorrhage, multiple noncontiguous intramural hemorrhages, and new vessels in and around the arterial wall were noteworthy findings in our series. All 20 reported autopsied cases of the vertebrobasilar artery have a dissection between the media and adventitia with a rupture site in the thin adventitia. Seventeen of them had disruption of the entire arterial wall, but the remaining three cases had no apparent luminal connection. The clinicopathological features of this disease are various. On the basis of the pathological investigations of these reported cases, the pathogenesis of this lesion is discussed. Intramural hemorrhage associated with dissection without luminal connection should not be disregarded as a causative factor.