Multichannel auditory brainstem implantation: the Australian experience

The multichannel auditory brainstem implant (ABI) provides the potential fo r hearing restoration in patients with neurofibromatosis type 2 (NF2). Prog rammes for auditory brainstem implantation have been established in two Aus tralian centres. Eight patients have been implanted under the protocol of a n international multi-centre clinical trial. Three patients had ABI inserti on at the time of first side tumour removal, four at second side tumour rem oval and one after previous bilateral surgery where there was some residual tumour. The translabyrinthine approach was used in all cases. Successful p ositioning of the electrode array was achieved in seven of eight patients, all of whom achieved auditory perception with electrical stimulation. Intra -operative electrically evoked auditory brainstem response testing was succ essful in four patients and was useful in confirming correct electrode posi tion. In six cases postoperative psychophysical and auditory perception tes ting demonstrated that useful auditory sensations were achieved. Five of th ese patients regularly used the implant. In one patient electrode placement was unsuccessful and only non-auditory sensations occurred on stimulation. In the remaining patients nonauditory sensations were minimal and avoidabl e by selective electrode programming. Auditory brainstem implantation shoul d be considered in patients with NF2. The greatest benefit is seen in patie nts without debilitating disease who have non-aidable hearing in the contra lateral ear.