[Enlarged retro-labyrinthic approach: application to surgery of acoustic neurinoma. Apropos of 55 cases].

The enlarged retro-labyrinthic route described here allows opening of the internal auditory canal, exeresis of tumors localized in the ponto-cerebellous angle and in the internal auditory canal. We used this route for 55 neurinomas of the auditory nerve (7.4% stage I, 23.6% stage II, 45.4% stage III and 23.6% stage IV). Most of the tumors in our series were > 2 cm. There were no post-operative deaths. Risk of fistulization was low, 3.8%. Post-operative meningitis (3.8%) regressed rapidly with treatment. Facial function outcome was equivalent to that obtained with the enlarged trans-labyrinthic route and reported in the literature in series treated via the sub-occipital route (83.6% for grades I and II, 11% for grade III). One patient required hypoglosso-facial anastomosis with a grade IV result at 6 months. Auditive function was preserved at a socially acceptable level in 14.5% of the patients and in 21.8% hearing aids were needed. Selecting a subgroup of 25 patients with good quality hearing prior to surgery (< 30 dB) and a tumor invading less than three-fourths of the internal auditory canal, for all tumor sizes, 28% preserved socially acceptable hearing. To these must be added 20% who had some hearing loss which could be corrected. The modulary mature of the retrolabyrinthic route is easily transposable to the trans-labyrinthic rout. Because of the potential for preserving auditive function this technique should replace the less flexible sub-occipital route.