Auditory Brainstem Implantation (ABI)—Feasibility of Revision Surgery

Introduction: ABI is an effective procedure for restoration of hearing. Due to different conditions a malfunction of the ABI system may occur. In such cases, the question arises if revision surgery is possible, effective with an acceptable risk versus benefit ratio. Objective: To investigate feasibility of revision surgeries in ABI. To describe the surgical problems, timing of operation, outcome, complications, and hearing benefit. Methods: Seven patients had been implanted with an ABI system (MedEl, Austria). Out of which six were NF2 and one had aplasia of the cochlea-vestibular nerve. Revision surgery was performed in five cases in semisitting position. Multimodal monitoring was used. Indication was loss of hearing or tumor regrowth. Results: Three cases had electrode displacement, one case had tumor regrowth, one acute rebleeding, and 2 patients had failure after fall. The interval between the first and revision surgery varied from 1 day to 6 years. Repositioning of the probe, complete change of ABI or tumor/bleeding removal was performed. Patients showed a fair to good improvement of their hearing. All patients are users after revision. The main surgical problem was scarring and dissecting the probe in the foramen of Luschkae. Conclusion: Revision surgery after ABI is feasible but in most cases difficult due to scarring around the brainstem. First line should be to avoid it by proper fixation of the probe and the implant housing (shoulder shadow). However, if indicated it is possible to perform successful repositioning and complete system changes, which is extremely important in pediatric cases. In patients with tumor regrowth it appears better to do an early intervention.