Objective: To investigate the surgical techniques and speech performance of multichannel auditory brainstem implant (ABI) in patients with bilateral acoustic neuromas (neurofibromatosis type 2).
Methods: The nucleus 21 channel auditory brainstem implant was implanted into the lateral recess of the fourth ventricle through the translabyrinthine approach in 7 patients after removal of the tumor. The accurate placement of electrode array was ensured by the electromyogram monitoring of the 7th and 9th nerves and the electrically evoked auditory brainstem responses (EABR). Initial switch-on occurred six weeks postoperatively. Speech evaluation was performed every 3 months for the first year and annually thereafter.
Results: During the surgery, the lateral recess could be found and the typical EABR could be recorded in 6 cases. They later reported a significant benefit from the device. Two of the cases have achieved functional open-set speech understanding. In contrast, one patient with no EABR because of difficulty of the anatomic location during the surgery had no sensations postoperatively.
Conclusion: The multichannel ABI could effectively restore auditory sensations in patients deafened by bilateral acoustic neuromas. The accurate location of the cochlear nucleus complex during surgery was the key factor for the success of the operation.