Effects of electrical brainstem stimulation on tinnitus.

The primary aim of the auditory brainstem implant (ABI), an investigational device, is to restore auditory sensations in neurofibromatosis-2 patients deafened by bilateral acoustic neuroma surgery. An electrode is placed on the dorsal cochlear nucleus after the tumor is removed through the translabyrinthine approach. This procedure was performed on 18 patients: 13 were completely deafferentated after bilateral tumor removal and had received the ABI during surgery on the second-sided tumor; 5 were implanted at first-sided tumor removal. Three of these 5 patients had usable hearing remaining on the side of the second acoustic neuroma and were stimulated only during laboratory sessions. All patients had tinnitus. We used a questionnaire to assess the effects of brainstem stimulation on this symptom. Of the 18 patients, one early patient deceased, and one patient with no follow-up was not included in this study. Six patients who were unable to use the ABI because of temporary hardware problems or side effects from electrical stimulation were also excluded. Thus, we studied 10 patients. Of 7 patients who used their implant daily, 6 reported noticeable tinnitus reduction; the ABI had no effect in the remaining case. Of 3 recently implanted patients who used this implant only during laboratory testing, one patient reported complete suppression of tinnitus, one described worse tinnitus, and one reported no effect.