Auditory brainstem implants in neurofibromatosis Type 2: is open speech perception feasible?

Abstract

Object Patients with bilateral auditory nerve destruction may perceive some auditory input with auditory brainstem implants (ABIs). Despite technological developments and trials in new stimulation sites, hearing is very variable and of limited quality. The goal of this study was to identify advantageous and critical factors that influence the quality of auditory function, especially speech perception. Methods The authors conducted a prospective study on ABI operations performed with the aid of multimodality neuromonitoring between 2005 and 2009 in 18 patients with neurofibromatosis Type 2. Outcome was evaluated by testing word recognition (monotrochee-polysyllabic word test at auditory-only mode [MTPa]) and open speech perception (Hochmair-Schulz-Moser [HSM] sentence test), both in pure auditory mode. The primary outcome was the HSM score at 24 months. The predictive meaning of general clinical data, tumor volume, number of active electrodes, duration of deafness, and early hearing data was examined. Results In 16 successful ABI activations the average score for MTPa was 89% (SD 13%), and for HSM it was 41% (SD 32%) at 24 months. There were 2 nonresponders, 1 after radiosurgery and the other in an anatomical variant. Direct facial nerve reconstruction during the same surgery was followed by successful nerve recovery in 2 patients, with a simultaneous very good HSM result. Patients' age, tumor extension, and tumor volume were not negative predictors. There was an inverse relationship between HSM scores and deafness duration; 50% or higher HSM scores were found only in patients with ipsilateral deafness duration up to 24 months. The higher the deafness sum of both sides, the less likely that any HSM score will be achieved (p = 0.034). In patients with total deafness duration of less than 240 months, higher numbers of active electrodes were significantly associated with better outcomes. The strongest cross-correlation was identified between early MTPa score at 3 months and 24-month HSM outcome. Conclusions This study documents that open-set speech recognition in pure auditory mode is feasible in patients with ABIs. Large tumor volumes do not prevent good outcome. Positive preconditions are short ipsilateral and short bilateral deafness periods and high number of auditory electrodes. Early ability in pure auditory word recognition tests indicates long-term capability of open speech perception.

Cochlear implantation improves hearing and vertigo in patients after removal of vestibular schwannoma

“…Considering the large number of the affected patients, early diagnosis and treatment of the disease is mandatory in order to achieve favourable results. However, the chances to preserve hearing decrease with increasing tumour size despite advanced surgical techniques and a high percentage of the patients experience severe to profound hearing loss [10][11][12][13] . Therefore, the demand for a sufficient hearing supply after surgical removal is rising.…”

“…The quantity and quality of hearing rehabilitation is increasing from normal hearing aids, cross-and bicross-hearing-systems, bone conducted hearing aids, middle ear implants (MOI), cochlear implantation (CI), auditory brainstem implant (ABI) and auditory midbrain implant (AMI). After surgical removal of VSs, especially in neurofibromatosis type 2 patients, the supply with ABI is in most cases an option, but several studies showed an unsatisfactory outcome 8,11,13,14 . Especially the speech perception with an ABI in adults 15 , compared to the supply in young children 16 , is a huge breakdown.…”

Auditory Brainstem Implantation in Neurofibromatosis Type 2

“…In only a very small number of individuals was performance with the ABI comparable to that expected from a cochlear implant, most of whom achieve open-set speech understanding and high sentence scores even in NF2 (9). While these results are comparable to the majority of studies evaluating the ABI5 (4,5,(9)(10)(11)(12)(13)(14), some recent publications have demonstrated a greater proportion of high performing users (15)(16)(17)(18). Explaining the discrepancy between outstanding results and limited audition remains the biggest challenge for teams working with the ABI.…”

“…They surmised that the effects of preoperative tumor size and surgical removal caused deleterious effects to the cochlear nucleus. More recently Matthies et al (15,16), and Behr et al (17), have demonstrated similar outcomes with NF2 patients as well, finding that tumor size did not affect their results. The two outstanding patients in our series had large tumors with brain stem compression; the best was in a young man presenting with two 4 cm tumors.…”

Interfacing with the nervous system: a review of current bioelectric technologies

“…For children suffering from bilateral, ossified cochlea secondary to meningitis, five out of the nine patients experienced a meaningful benefit from ABI, with access to conversational speech and sound field thresholds varying from 25 to 50 dB [8]. Although historically NF2 patients have had exceedingly limited benefit from ABIs due to the detrimental nature of the tumors, more recent studies from Europe have reported considerable success in ABI performance in NF2 patients, including a mean open-set speech perception of 41% at 24 months post-ABI activation in 18 NF2 patients [77]. Notably, a penetrating ABI and an auditory midbrain implant inserted into the inferior colliculus did not lead to an increased benefit over the ABI [69,70,138].…”