PRESENTATION OF FACIAL, COCHLEAR, AND OTHER NERVE FUNCTIONS IN ACOUSTIC NEUROMA TREATMENT

Between March 1966 and September 1992, 1400 acoustic neuromas were tre ated in Paris, France, by surgical excision. The findings over the las t 7 years are presented. The translabyrinthine approach has been used in more than 85% of cases. Where hearing preservation is attempted, th e middle fossa approach has been adopted for intracanilicular tumors a nd the refrosigmoid approach for Small tumors extending into the cereb ellopontine angle, in which the fundus of the internal meatus is free of tumor. The main goal is to achieve a grade I or II result in facial function within I month of surgery. Results improved during 1991 afte r the introduction of continuous facial nerve monitoring and the use o f the Beaver mini-blade for dissection of tumor from nerve. With these techniques, facial function at grade I or II at 1 month improved from 20% to 52% for large tumors (larger than 3 cm), from 42% to 81% for m edium tumors (2 to 3 cm), and from 70% to 92% for small tumors (up to and including 2 cm extracanalicular). The facial nerve was at greater risk using the retrosigmoid or middle fossa approaches than by the tra nslabyrinthine route. Since 1985, success in hearing preservation has changed little, with useful hearing being preserved in 38.2% of cases operated on by means of the retrosigmoid route and 36.4% of cases afte r the middle fossa approach. In older patients with good hearing and s mall tumors, observation with periodic MRI scanning is recommended. De spite earlier diagnosis, the number of patients suitable for hearing p reservation surgery remains very limited and careful selection is requ ired. Trigeminal nerve signs were present in 20% of cases preoperative ly, in 10% postoperatively, and recovered spontaneously. Palsies of th e other cranial nerves after surgery were much rarer and were as follo ws: sixth nerve (abducens), 0.5%; ninth nerve (glossopharyngeal), 1.4% ; and tenth nerve (vagus), 0.7%. the importance of preservation of fun ction of the nervus intermedius of Wrisberg is stressed. These results emphasize the advantages of the translabyrinthine approach, offering greater security to the facial nerve and lower morbidity.