Auditory Brainstem Implantation in Neurofibromatosis Type 2

Abstract

Objective: To describe the experience of auditory brainstem implantation (ABI) in patients with Neurofibromatosis type 2 (NF2). Results: There were 50 primary ABI insertions in 49 patients, including 16 inserted at the time of first side tumor removal as a sleeper, and two revision repositionings which failed to improve outcome. Postoperatively three patients had cerebrospinal fluid leaks which did not require reoperation, one patient had meningitis, and eight patients suffered either temporary or permanent lower cranial nerve dysfunction. Twenty-nine patients became full time users; a further 12 patients became non-users. Three patients died while their device was inactive. Five patients retain serviceable contralateral hearing. Audiological open set testing of users showed means of: environmental sounds discrimination 51%; phoneme discrimination: with ABI alone 22%/lip reading (LR) 45%/ABI with LR 65%; sentence testing: with ABI alone 13%/LR 19%/ABI with LR 54%. Conclusions: The majority of patients with NF2 implanted with an ABI find the device a useful aid to communication in conjunction with LR and in recognizing common environmental sounds. A small proportion gain open set discrimination. Almost a third of patients may end up as non-users. There is probably an increased risk of postoperative lower cranial nerve dysfunction so careful preoperative assessment is advised.Key Words: Auditory brainstem implantBilateral deafness-Postoperative complications-SurgeryVestibular schwannoma.Otol Neurotol 37:xxx-xxx, 2016.The auditory brainstem implant (ABI) evolved from cochlear implant technology to rehabilitate those individuals with total bilateral deafness who are unsuitable for cochlear implantation because of non-functional cochlear nerves or unimplantable cochleas. The majority of candidates suffer from the genetic disorder neurofibromatosis type 2 (NF2) which causes bilateral vestibular schwannomas leading to deafness either by direct damage from the tumors themselves or from the surgery to remove them (1). The ABI stimulates the cochlear nucleus complex directly, which is readily accessible after vestibular schwannoma removal.The Manchester programme participated in the original European pilot study (2), and since then has routinely offered it to appropriate patients. This article reviews our experience in NF2 patients. MATERIAL AND METHODS PatientsPatients were included in the study if they met the Manchester criteria for NF2 disease (3), and had been implanted with an ABI and had continued rehabilitation by the Manchester team between 1994 and 2009.

Hearing optimisation in neurofibromatosis type 2: A systematic review

“…The number of active electrodes may be important although the evidence is contradictory. Ramsden et al . found a positive correlation although Behr et al .…”

“…Forty papers relevant to ABI in NF2 were identified. Fifteen presented audiological data that were not repeated in other publications although it is likely that there was still some duplicate reporting . There was considerable variability in the type of implant used.…”

“…The non‐user rate was 13.2%. It is important to note that the auditory benefit from ABI continues to improve over several years and in this way differs from CI where most of the improvement is seen in the first year . Therefore, ABI only infrequently allows open set speech discrimination and for the majority of patients provides assistance in lip reading.…”

“…Surgical position may also influence outcome with some authors suggesting that the semi‐sitting position provides better outcomes . Other possible factors important for optimising outcome include duration of deafness prior to implantation, quality of the intra‐operative and post‐operative EABR and ABI stimulation rate although the evidence is again contradictory . Tumour size and age at surgery do not appear to influence outcome …”

Re-implantation of an auditory brainstem implant (ABI) in a child: A case report

“…Ramsden et al [16] described two revision cases with repositioning of the electrode plate. In both cases, there was dense scar tissue around the array and a combination of blunt and sharp dissection was required to mobilise it.…”