Optic neuropathy and sixth cranial nerve palsy caused by compression from a dolichoectatic basilar artery.

A 53-year-old man with progressive visual loss in the right eye and diplopia manifested dysfunction of the right optic nerve and the right sixth cranial nerve. MRI revealed a markedly enlarged and tortuous basilar artery, its proximal portion compressing the right sixth cranial nerve at the exit from the pons and its distal portion elevating and compressing the right optic nerve. This is the first report of optic neuropathy and sixth cranial nerve palsy caused by a dolichoectatic basilar artery.