[Microsurgical neurolysis of the 8th cranial nerve in cochleo-vestibular disorders using an extended transtemporal approach].

A series of 17 patients suffering from progressive cochleovestibular disturbances (8), severe attacks of Menière's disease (5), progressive or sudden sensori-neural deafness (2), vestibular neuronitis (1) or unbearable tinnitus (1) is reported. The eighth cranial nerve was exposed from its root at the brainstem to its exit into the fundus of the internal auditory canal (CAI), by an extended middle fossa approach. The surgical technique and the intraoperative observations are described. All cases showed morphological abnormalities such as neuro-vascular compression of the nerve by arterial or venous vessels, either at the brainstem or laterally at the CAI. Horizontal or vertical dislocations of the nerve were also noticed. Traction, compression or even strangulation of the nerve fibres or of their accompanying vessels may be co-factors of the functional disturbances. Striking improvement of the vestibular disorders was recorded following neurolysis of the eighth nerve, showing that retrolabyrinthine abnormalities may be possible causes of Menière's disease and other supposedly labyrinthine disorders. The preliminary results regarding hearing and tinnitus were hitherto unsatisfactory. This fact may be explained by the, as yet, imperfect technique of neurolysis.