Rupture of an experimentally induced aneurysm in a primate.

Cerebral aneurysms are extremely rare in all animals except man. We report the occurrence of a carotid-ophthalmic aneurysm in a cynomolgous monkey two months following accidental occlusion of the ipsilateral cervical internal carotid artery. This was documented angiographically. The aneurysm was deliberately ruptured by the insertion and withdrawal of fine needles. This produced a large subarachnoid hemorrhage visualized on CT scan. There was a progressive severe fall in cerebral blood flow and moderate vasospasm. The neurological status deteriorated on the tenth day and the animal was sacrificed on day 13. On electron microscopy, the aneurysm showed a fibrous wall, and the endothelium showed balloon-like endothelial cells with gaps. Corrugations occurred in the inner aspect of the anterior circulation arteries.