Traumatic production of an intracranial berry-like aneurysm in a monkey.

A berry-like dissecting intracranial aneurysm resulted from inadvertent puncture of the internal carotid artery during trans-palatal section of a monkey's optic nerve. The light and ultrastructural features are rather similar to those of human berry aneurysms supporting the notion that the latter are degenerative rather than congenital in origin.