Auditory brainstem implant (ABI): new frontiers in adults and children.

UNLABELLED: Previous studies have considered only patients with neurofibromatosis type 2 (NF2) older than 12 years as candidates for an auditory brainstem implant (ABI). Our study expands the potential criteria to include both children and adult subjects with other cochlear or cochlear nerve malfunctions who either would not benefit at all from a cochlear implant (eg, cochlear nerve aplasia or avulsion) or whose benefit was or would be severely compromised (eg, cochlear ossification, cochlear fracture). STUDY DESIGN: In our department, over the period from April 1997 to September 2002, 29 patients, 20 adults and 9 children, were fitted with ABIs. Their ages ranged from 14 months to 70 years. Thirteen subjects had tumors, 10 NF2 and 3 solitary vestibular schwannoma, and 16 patients had a variety of nontumor (NT) cochlear or cochlear nerve diseases. A retrosigmoid-transmeatal approach was used in T and a retrosigmoid approach in NT patients. The electrode array was inserted into the lateral recess of the fourth ventricle and correct electrode positioning was monitored with the aid of electrically evoked auditory brainstem responses (EABRs). RESULTS: Correct implantation was achieved in all patients. No complications were observed due to implantation surgery or related to ABI activation or long-term use. Auditory sensations were induced in all patients with various numbers of electrodes (from 5 to 15). Different pitch sensations were identifiable with different electrode stimulation. Closed-set word recognition, open-set sentence recognition, and speech tracking scores achieved by the patients are reported in detail. The auditory performance of the patients showed significantly better outcomes than controls (Multicentric European clinical investigations on ABI with NF2). CONCLUSION: We have shown that the indications for the ABI can be extended to include NT patients with severe cochlear and/or cochlear nerve abnormalities. The degree of auditory benefit varies as a function of the underlying pathological conditions, with NT subjects exhibiting significantly better outcomes than the T patients.

Cochlear implantation at under 12 months: report on 10 patients.

OBJECTIVES: There is growing evidence that early application of a cochlear implant in children affected by profound congenital hearing loss is of paramount importance for the development of an adequate auditory performance and language skills. For these reasons and as a result of advances in audiologic diagnosis and an enhanced awareness of the safety of cochlear implants, the age of implantation has substantially decreased over recent years. Children aged as little as 12 months are now being implanted in some centers. On the basis of our experience with very young children, we believe that the date of implantation may be further reduced to only 4 to 6 months of age. STUDY DESIGN: Over the period from November 1998 to April 2004, 103 children have been fitted with cochlear implants and 11 with auditory brainstem implants in our department, including 65 children aged below 3 years. The present study focuses on 10 children aged less than 12 months fitted with cochlear implants from November 1998 to December 2003. METHODS: The children's ages ranged from 4 to 11 (mean 9.5) months. Five were males and five females. All received a Nucleus CI 24 M. Postoperative auditory performance, as evaluated at the latest follow-up, was based on the category of auditory performance (CAP). The results obtained in these 10 children were compared with those obtained with cochlear implants in children belonging to older age brackets. The criteria used to assess speech performance were onset of babbling onset and babbling spurt, and the results observed were compared with those of a control group of 10 normally hearing children. RESULTS: Surgery was uneventful, and no immediate or delayed complications were encountered. Auditory performance was seen to increase as function of early age of implantation and length of implant use. All 10 children had a CAP score of 3 within 6 months of cochlear implant activation. The onset of babbling occurred very early (i.e., within 1 to 3 months of activation of the implant in all 10 patients), regardless of age at implantation, whereas the babbling spurt was recorded at times ranging from 3 to 5 months after implant activation. The positive impact of early implantation on babbling was clearly shown by the fact that the earlier the activation of the cochlear implant, the closer the results were to the outcomes of normally hearing children. CONCLUSIONS: We encourage very early implantation to facilitate a series of developmental processes occurring in the critical period of initial language acquisition. The indices we used in the present study (i.e., CAP and babbling) suggest that early cochlear implantation tends to yield normalization of audio-phonologic parameters, which enables us to consider the performance of children implanted very early as being similar to that of their normally hearing peers.

Auditory brainstem implant as a salvage treatment after unsuccessful cochlear implantation.

OBJECTIVE: The present article investigates on an individual basis the performance achieved with the auditory brainstem implant in patients who had been treated unsuccessfully with a cochlear implant. STUDY DESIGN: An intrasubject comparison between results achieved with the cochlear implant and the auditory brainstem implant is reported. SETTING: Tertiary referral care. PATIENTS: Five subjects were fitted with an auditory brainstem implant in our department because of the poor results achieved with cochlear implants. Two were children, one with bilateral cochlear nerve aplasia and one suffering from auditory neuropathy. Three were adults with complete cochlear ossification. INTERVENTION: A retrosigmoid approach was used in all subjects. Electrically evoked auditory brainstem responses and neural response telemetry were used to monitor electrode positioning. RESULTS: No complications were observed due to implantation surgery or related to activation or long-term use of the auditory brainstem implant. Auditory sensations were induced in all patients with varying numbers of electrodes (from 9-16). In all three adults, the cochlear implant did not allow either word/sentence discrimination or speech tracking, whereas the auditory brainstem implant permitted discrimination of two- or three-syllable words with scores from 85 to 100%. In the two adults with a follow-up of 5 and 6 months after auditory brainstem implant activation, the open-set sentence recognition scores (auditory-only mode) were 70% and 100%, respectively, and the speech-tracking scores were 27 and 40 words/min, respectively. One patient with a follow-up of only 3 months scored 0% in both sentence recognition and speech tracking. The two children who had achieved no hearing ability with the cochlear implant were already able to detect sounds and words as early as 2 months after activation of the auditory brainstem implant and are showing progressive improvement in their performance. CONCLUSION: Auditory brainstem implantation may be a very powerful rehabilitative treatment after cochlear implant failure. The possibility of using the auditory brainstem implant as first-choice therapy in some categories of deaf patients (e.g., subjects with auditory neuropathy or cochlear ossification) who are currently treated with cochlear implantation is discussed.

Cochlear implant failure: is an auditory brainstem implant the answer?

OBJECTIVE: To investigate the auditory rehabilitative results achieved in five patients with cochlear implants (CIs) who subsequently received, due to poor results, auditory brainstem implants (ABIs). MATERIAL AND METHODS: Between April 1997 and March 2003, 37 patients (age range 14 months to 70 years) were fitted with ABIs in our ENT Department. Fourteen subjects had neurofibromatosis type 2 and 23 were non-tumor patients who had cochlea or cochlear nerve disease. Five subjects had previously been treated with a CI and received an ABI owing to the poor results achieved. One child had bilateral undiagnosed cochlear nerve aplasia and one was suffering from auditory neuropathy; three adults had total cochlear ossification. RESULTS: The open-set sentence recognition score (auditory-only mode) 6-8 months after ABI activation ranged from 0% to 100% in adults. In 1 subject the speech-tracking score was 56 words/min with the ABI. The two children who had achieved no hearing ability with their CI were able to detect sounds and words as early as 3 months after activation of the ABI. CONCLUSION: CI failure as a result of anatomical abnormalities can be remedied by an ABI.

Hearing restoration with auditory brainstem implant in three children with cochlear nerve aplasia.

OBJECTIVE: To verify the possibility of auditory habilitation in children with aplasia and hypoplasia of the cochlear nerve by direct electrical stimulation of the cochlear nuclei with an auditory brainstem implant. STUDY DESIGN: Retrospective case review. SETTING: Study conducted at the Ear, Nose, and Throat Department of the University of Verona, Italy. PATIENTS: Three children, aged 4, 3, and 2 years, respectively, with severe bilateral cochlear malformations and cochlear nerve aplasia have received an auditory brainstem implant at this institution in the past 2 years. INTERVENTION: The classic retrosigmoid approach was used. Correct positioning of the electrodes was evaluated using electric auditory brainstem responses and neural response telemetry. Before the patients were discharged, high-resolution computed tomography with a bone algorithm reconstruction technique was performed to evaluate electrode placement. The auditory brainstem implant was activated 30 to 60 days after implantation. RESULTS: No postoperative complications were observed. To date, 21, 18, and 8 electrodes, respectively, have been activated in the three children. The first patient, 12 months after activation, had achieved good environmental sound awareness, good speech detection, and some speech recognition. The second child, 8 months after activation, had achieved good environmental sound awareness and moderate speech detection. The third patient, 1 month after activation, had obtained good environmental sound awareness. CONCLUSION: This study indicates that auditory brainstem implantation is technically feasible in children with cochlear nerve aplasia. The early results suggest the possibility of achieving auditory habilitation with auditory brainstem implantation in this population.

Auditory brainstem implantation: the University of Verona experience.

OBJECTIVE: We sought to describe the advantages of the retrosigmoid-transmeatal (RS-TM) approach in the application of auditory brainstem implants (ABIs) in adults with monolateral and bilateral vestibular schwannoma (VS) and in children with cochlear nerve aplasia. STUDY DESIGN: We conducted a retrospective case review. SETTING: The study was conducted at the ENT Department of the University of Verona, Italy. PATIENTS: Six adult patients (5 men and 1 woman) with neurofibromatosis type 2 (NF2) were operated on for VS removal with ABI. An additional patient had a unilateral VS in the only hearing ear. Tumor size ranged from 12 to 40 mm. In addition, 2 children received ABIs for bilateral cochlear nerve aplasia. INTERVENTION: An RS-TM approach was used in all VS patients, and an RS approach was used in the subjects with cochlear nerve aplasia. After tumor excision, landmarks (VII, VIII and IX cranial nerves, choroid plexus) for the foramen of Luschka were carefully identified. The choroid plexus was then partially removed and the tela choroidea divided and bent back; the floor of the lateral recess of the fourth ventricle and the convolution of the dorsal cochlear nucleus became visible. In the 2 subjects with no cochlear nerve, the choroid plexus and VII and IX cranial nerves were used as landmarks. The electrode array was then inserted into the lateral recess and the correct position was monitored with the aid of electrically evoked auditory brainstem responses (EABR) and neural response telemetry (NRT). RESULTS: Correct implantation was possible in all patients. Auditory sensations were induced in all patients with various numbers of electrodes. Different pitch sensations could be identified with different electrode stimulation. CONCLUSIONS: We believe that the RS approach is the route of choice for patients who are candidates for ABI due to the easy and clear access to the cochlear nucleus area. This route avoids some of the drawbacks of the translabyrinthine approach, such as mastoidectomy, labyrinthectomy, sealing of the cavity and posterior fossa with abdominal fat, and contamination from the middle ear. For this reason, it is the route of choice in children with cochlear nerve aplasia or severe cochlear malformation and in adults with complete ossification of the cochlea or cochlear nerve disruption due to cranial trauma.