[Giant thrombosed aneurysm of the left vertebral artery developing in the fourth ventricle].

A case of giant, thrombosed, non haemorrhagic aneurysm of the distal portion of the left vertebral artery is reported. The patient came to medical attention with an acute cervical pain after a minimal cervical traumatism and a diagnosis of torticollis from rheumatologic cause was made. In fact, a few weeks before, he had suffered three episodes of right homonymous hemianopsia. Subsequently, hiccup, vomiting, orthostatic dizziness with postural hypotension appeared, suggesting a medullary lesion. CT scan showed a round, heterogeneous high-density lesion near the fourth ventricle. Angiography was normal. MRI showed an oval mass in the fourth ventricle, between the medulla and the cerebellum. Surgery found an aneurysm of the end of the left vertebral artery.