Cochlear Implantation after Acoustic Tumour Resection in Neurofibromatosis Type 2: Impact of Intra- and Postoperative Neural Response Telemetry Monitoring

Abstract

The present paper reports about a 16-year-old male with neurofibromatosis type 2 (NF-2) of the Wishart type with bilateral deafness who had undergone cochlear implantation after resection of the acoustic neuroma (AN) of the same side. Neural response telemetry (NRT) recordings are essential in those patients during cochlear implantation where no stapedial reflexes can be electrically elicited due to the resection of the AN. In the present case, amplitude growth function and a type II pattern of the NRT waveforms could be well established. The comparison of the N₁ response intra-operatively and after 2 years showed a decline in latency by 50% and an increase in absolute amplitude by 10 times at the same current level of electrical stimulation. This improved auditory nerve transduction suggested a change to a ‘faster’ encoding strategy to improve speech understanding. The change from SPEAK to ACE 18 months after the operation led to an increase in the open-set sentence recognition test from 52 to 88%. Thus, NRT recordings monitor the intra-operative success of electrode placement and help to assess the integrity of the auditory pathway. Moreover, they can reliably be used in programming the speech processor postoperatively as objective tool. In patients with NF-2, the restoration of hearing can be successfully achieved in several ways. The indications for hearing implants (auditory brain stem and cochlear implants) should be carefully considered with respect to the remaining, functional integrity of the auditory nerve and the technical possibilities to monitor the success of these procedures.

Hearing Rehabilitation in Neurofibromatosis Type 2 Patients: Cochlear versus Auditory Brainstem Implantation

“…In the 1990s, Cueva [1992] reported on auditory sensations elicited by electrical promontory stimulation (EPS) in a patient with preserved cochlear nerve and deafness after VS resection, demonstrating the theoretical feasibility of cochlear implantation in deafened NF2 patients with intact cochlear nerve after VS removal. Since then, histological [Belal, 2001] and clinical studies Hulka et al, 1995;Tono et al, 1996;Graham et al, 1999;Ahsan et al, 2003;Nolle et al, 2003;Aristegui and Denia, 2005] confirmed that cochlear implantation is possible in at least a subset of this special population of patients. Today, we can offer 2 options for hearing restoration, cochlear or auditory brainstem implantation, to NF2 deafened patients with an anatomically preserved cochlear nerve.…”

Hearing optimisation in neurofibromatosis type 2: A systematic review

“…Again, this technique is limited to tumours of <15 mm in the cerebellopontine angle, unless there is a subtotal resection. There were 13 papers in total in this group with 16 ears who had retrosigmoid surgery and five ears in the group that had had middle fossa surgery . Useful data were available in all but one case.…”

“…There were 13 papers in total in this group with 16 ears who had retrosigmoid surgery and five ears in the group that had had middle fossa surgery. 50,64,65,68,[72][73][74][75][76] Useful data were available in all but one case.…”

Retrolabyrinthine approach for cochlear nerve preservation in neurofibromatosis type 2 and simultaneous cochlear implantation

“…Cueva et al 5 elicited auditory sensation through electrical promontory stimulation in 6 patients with NF2 who underwent tumor removal with cochlear nerve preservation. Since then, about 31 cases of cochlear implantation in NF2 patients have been reported in the literature 6 7 8 9 10 11 12 13 14 15 16 . The timing of implantation varied from simultaneously to 10 years after tumor resection.…”