The high rate cis auditory brain stem implant for restoration of hearing in NF-2 patients

On the basis of the promising results in CI patients provided with the high rate CIS strategy the ENT and Neurosurgical Clinic of the University of Würzburg started an ABI program in 1997. The 12 channel Med-El device Combi 40/40+ was used and a special electrode for insertion into the lateral recess of the 4th ventricle was developed. The surgical procedure is performed by a team of ENT-neurosurgeons and audiologists. The retrosigmoid approach in a semi-sitting position of the patient is used. Sixteen probes in 15 patients were implanted, one successfully revised due to probe dislocation. In one additional patient hearing was preserved who is now provided with a conventional hearing aid. In another patient the 8th nerve was anatomically preserved due to the retrosigmoid approach and a CI could be implanted after positive promontory test. The same situation occurred in a recent patient who will be examined in the near future by a promontory test. In case of positive results a CI will be implanted. In one patient the planned implantation was not possible due to a vascular abnormality in the lateral recess. One patient of the 15 implanted patients is a non user, the others use the implant on a daily basis. They have tonotopy, sound discrimination and are able to perceive daily life and warning sounds. The average increase of lip reading is 30%. More than 50% have open speech understanding at different performance levels. Complications attributed to ABI implantation are mainly CSF leakage. In summary, ABI implantation is a reliable and safe method for hearing rehabilitation and restoration in NF-2 patients.