Successful removal of an angiographically occult arteriovenous malformation of the ventral medulla.

A case with an angiographically occult arteriovenous malformation (AVM) of the ventral medulla presenting with progressive motor and sensory deficits is reported. The AVM, about 1 x 1 x 0.5 cm in size, accompanied by intramedullary haematoma, was successfully removed through a small incision placed in the right ventrolateral medulla between the vagus and the hypoglossal nerves. The patient's neurological symptoms improved after surgery.