Basilar artery giant fusiform aneurysms caused by congenital defect of the internal elastic lamina and media.

Giant fusiform aneurysms of the basilar artery were found in a 6-year-old boy who subsequently died after rupture of the aneurysm, and in a 64-year-old man who showed signs of ischemia and compression of the brain stem. Autopsy disclosed strikingly similar abnormalities of the wall of the basilar artery, consisting of a defect of the internal elastic lamina and absence of the media. A congenital anomaly may play a role in the pathogenesis of this abnormality, in both young and some elderly patients.