The development of auditory perception in children after auditory brainstem implantation.

Auditory brainstem implants (ABIs) can provide useful auditory perception and language development in deaf children who are not able to use a cochlear implant (CI). We prospectively followed up a consecutive group of 64 deaf children up to 12 years following ABI surgery. The etiology of deafness in these children was: cochlear nerve aplasia in 49, auditory neuropathy in 1, cochlear malformations in 8, bilateral cochlear postmeningitic ossification in 3, neurofibromatosis type 2 in 2, and bilateral cochlear fractures due to a head injury in 1. Thirty-five children had other congenital nonauditory disabilities. Twenty-two children had previous CIs with no benefit. Fifty-eight children were fitted with the Cochlear 24 ABI device and 6 with the MedEl ABI device, and all children followed the same rehabilitation program. Auditory perceptual abilities were evaluated on the Categories of Auditory Performance (CAP) scale. No child was lost to follow-up, and there were no exclusions from the study. All children showed significant improvement in auditory perception with implant experience. Seven children (11%) were able to achieve the highest score on the CAP test; they were able to converse on the telephone within 3 years of implantation. Twenty children (31.3%) achieved open set speech recognition (CAP score of 5 or greater) and 30 (46.9%) achieved a CAP level of 4 or greater. Of the 29 children without nonauditory disabilities, 18 (62%) achieved a CAP score of 5 or greater with the ABI. All children showed continued improvements in auditory skills over time. The long-term results of ABI surgery reveal significant auditory benefit in most children, and open set auditory recognition in many.

Auditory brainstem implantation after unsuccessful cochlear implantation of children with clinical diagnosis of cochlear nerve deficiency.

OBJECTIVES: We compared the perceptual auditory abilities of 21 children with suspected cochlear nerve deficiency (CND) and a surgically verified absent cochlear nerve (CN) who first underwent cochlear implantation (CI) and subsequently underwent auditory brainstem implantation (ABI). METHODS: In this retrospective cohort study, from 2000 to 2011, 21 children initially underwent CI at an outside institution and failed to progress in their perceptual auditory abilities. Before CI, all of the children had severe to profound sensorineural hearing loss and a diagnosis of CND. Magnetic resonance imaging (MRI) documented an absent CN in 13 children and a small CN in 8 children. We performed explantation of the cochlear implant and simultaneous ABI on the same side. We performed MRI if no previous MRI results were available. All surgical videos were reviewed to determine the presence or absence of the CN. Measures of the patients' perceptual auditory abilities obtained after CI and after ABI were converted to the Category of Auditory Performance (CAP) scale. RESULTS: At surgery, all patients demonstrated an absent CN. After CI, all patients had a CAP score of 2 or less (mean, 0.52 +/- 0.68). After ABI, all patients had a CAP score of 2 or more (mean, 4.33 +/- 1.68); the improvement was statistically significant (p < 0.001). The complication rates were similar for CI and ABI. CONCLUSIONS: In this cohort of patients who had poor performance after CI, ABI achieved significantly improved performance as measured by the CAP and was shown to successfully rehabilitate hearing. Cases of a small CN may in reality represent an absent CN. Although this cohort was selected from patients with failed CI, the results have implications for the selection of device for patients with CND, in that ABI is a potential alternative to CI in select cases. In patients who fail to progress with intensive rehabilitation with CI or who have no progression in evoked auditory brainstem response, ABI must be considered early.

A Retrospective Evaluation to Assess Reliability of Electrophysiological Methods for Diagnosis of Hearing Loss in Infants.

Background: An electrophysiological investigation with auditory brainstem response (ABR), round window electrocochleography (RW-ECoG), and electrical-ABR (E-ABR) was performed in children with suspected hearing loss with the purpose of early diagnosis and treatment. The effectiveness of the electrophysiological measures as diagnostic tools was assessed in this study. Methods: In this retrospective case series with chart review, 790 children below 3 years of age with suspected profound hearing loss were tested with impedance audiometry and underwent electrophysiological investigation (ABR, RW-ECoG, and E-ABR). All implanted cases underwent pure-tone audiometry (PTA) of the non-implanted ear at least 5 years after surgery for a long-term assessment of the reliability of the protocol. Results: Two hundred and fourteen children showed bilateral severe-to-profound hearing loss. In 56 children with either ABR thresholds between 70 and 90 dB nHL or no response, RW-ECoG showed thresholds below 70 dB nHL. In the 21 infants with bilateral profound sensorineural hearing loss receiving a unilateral cochlear implant, no statistically significant differences were found in auditory thresholds in the non-implanted ear between electrophysiological measures and PTA at the last follow-up (p > 0.05). Eight implanted children showed residual hearing below 2000 Hz worse than 100 dB nHL and 2 children showed pantonal residual hearing worse than 100 dB nHL (p > 0.05). Conclusion: The audiological evaluation of infants with a comprehensive protocol is highly reliable. RW-ECoG provided a better definition of hearing thresholds, while E-ABR added useful information in cases of auditory nerve deficiency.

Intraoperative observation of changes in cochlear nerve action potentials during exposure to electromagnetic fields generated by mobile phones.

BACKGROUND: The rapid spread of devices generating electromagnetic fields (EMF) has raised concerns as to the possible effects of this technology on humans. The auditory system is the neural organ most frequently and directly exposed to electromagnetic activity owing to the daily use of mobile phones. In recent publications, a possible correlation between mobile phone usage and central nervous system tumours has been detected. Very recently a deterioration in otoacoustic emissions and in the auditory middle latency responses after intensive and long-term magnetic field exposure in humans has been demonstrated. METHODS: To determine with objective observations if exposure to mobile phone EMF affects acoustically evoked cochlear nerve compound action potentials, seven patients suffering from Ménière's disease and undergoing retrosigmoid vestibular neurectomy were exposed to the effects of mobile phone placed over the craniotomy for 5 min. RESULTS: All patients showed a substantial decrease in amplitude and a significant increase in latency of cochlear nerve compound action potentials during the 5 min of exposure to EMF. These changes lasted for a period of around 5 min after exposure. DISCUSSION: The possibility that EMF can produce relatively long-lasting effects on cochlear nerve conduction is discussed and analysed in light of contrasting previous literature obtained under non-surgical conditions. Limitations of this novel approach, including the effects of the anaesthetics, craniotomy and surgical procedure, are presented in detail.

Evidence of gadolinium distribution from the endolymphatic sac to the endolymphatic compartments of the human inner ear.

To verify whether injection of substances into the endolymphatic sac (ES) diffuses into the endolymphatic compartments of the human inner ear and in particular to the endolymphatic space of the scala media (ESp-SM), as demonstrated in animals, an exploratory investigation with magnetic resonance imaging (MRI) and intraoperative electrocochleographic recordings (ECoG) was conducted in patients with Ménière's disease (MD) treated with ES decompression. A mixture of dexamethasone and gadolinium (GD) in solution was injected into the ES of 4 patients. The results of the ES injection procedure were compared with administration of the same solution intratympanically (IT, 1 patient) and via a platinotomy in 2 patients. The study was conducted retrospectively at a tertiary referral center. Main outcomes measures were pre- and postintervention complete audiological and neuro-otological evaluation; intraoperative ECoG investigation with evaluation of the morphology of acoustically elicited compound action potentials (CAPs) and 1.5 T MRI evaluations at different follow-up times. Distribution of GD from the ES injection procedure was observed first in the ES, after 24 h in the vestibule and semicircular canals, and after 24-48 h in the ESp-SM in all patients. High signal was detected within the inner ear for 1 week or more (mean: 10 days; range: 7-16 days). Changes in morphology and latency of CAPs were observed within 30 min of the dilatory injection into the ES in all patients. Administration of GD into the vestibule and the IT approach did not distribute the contrast in the ES and GD was observed in the perilymphatic space of the vestibule, cochlea and semicircular canals. No side effects relating to administration of GD into the ES, IT or into the vestibule were observed. To the best of our knowledge this is the first demonstration in humans that drugs injected into the endolymphatic structure of the ES diffuse to the cochlea, presumably into the ESp-SM. The possibility of injecting substances into the endolymphatic space might open up new prospects in the treatment of inner ear disorders. Further studies will be needed to define the limitations of this approach.

Auditory results after vestibular nerve section and intratympanic gentamicin for Ménière's disease.

OBJECTIVE: Hearing loss is a possible complication of vestibular neurectomy and intratympanic gentamicin administration in Ménière's disease. The aim of this study was to compare the incidence of this complication with the two treatments. STUDY DESIGN: Retrospective review. SETTING: Tertiary referral center. PATIENTS: The initial study population reviewed consisted of 24 patients receiving gentamicin injections and 209 patients undergoing vestibular nerve section. Comparison of data was performed among all 24 intratympanic gentamicin patients and the last 24 vestibular neurectomy patients operated on via the retrosigmoid approach. INTERVENTIONS: Intratympanic gentamicin administration (26-156 mg) and retrosigmoid vestibular neurectomy. MAIN OUTCOME MEASURE: Auditory and vertigo results were evaluated according to the American Academy of Otolaryngology 1995 criteria. RESULTS: The mean preoperative pure-tone average for patients undergoing vestibular nerve section was 48.5 dB, with a speech discrimination score of 85%. In these patients, the postoperative pure-tone average was 50.3 dB, and the speech discrimination score was 82%. Patients undergoing gentamicin injection had a mean pretreatment pure-tone average of 50.1 dB and a speech discrimination score of 87%. The posttreatment pure-tone average and discrimination score for the gentamicin group were 74.7 dB and 65%, respectively. The amount of postprocedure hearing loss was significantly greater in the gentamicin group (p = 0.03). Excellent control of vertigo (classes A and B) was obtained in 95.8% of the patients treated with vestibular nerve section and in 75% of the patients in the gentamicin group. CONCLUSION: Gentamicin administration and vestibular neurectomy are both effective for relieving vertigo in Ménière's disease. The incidence of hearing loss is significantly higher after gentamicin injection.

The first successful case of hearing produced by electrical stimulation of the human midbrain.

HYPOTHESIS: Electrical stimulation of the inferior colliculus in the midbrain can provide a safe and efficacious alternative to auditory brainstem implants (ABIs). BACKGROUND: Patients with neurofibromatosis type 2 (NF2) receive limited speech recognition with ABIs. Some ABI patients without NF2 can achieve excellent speech understanding, suggesting that the limited NF2 performance is due to brainstem damage from the tumor and its removal. METHODS: An array of electrodes (Med-El ABI) was placed on the dorsal surface of the inferior colliculus in the midbrain of a human volunteer as an auditory prosthesis via an infratentorial supracerebellar median surgical approach. Electrophysiological responses, psychophysical responses, and speech recognition were measured. RESULTS: Electrical stimulation produced auditory sensations on all 12 electrodes with no nonauditory sensations. Auditory threshold levels indicated the stability of the electrode array over time. Electrophysiological measures showed activation in the contralateral auditory cortex but none in ipsilateral cortex. All electrodes demonstrated a full range of loudness sensation and electrode-specific pitch sensations. Speech recognition was significant, but limited in the first month after surgery. CONCLUSION: This approach may provide advantages for patients with brainstem damage.

Resorbable Mesh Cranioplasty Repair of Bilateral Cerebrospinal Fluid Leaks Following Pediatric Simultaneous Bilateral Auditory Brainstem Implant Surgery.

OBJECTIVE: To present a child with cochlear nerve deficiency (CND) who received simultaneous bilateral simultaneous auditory brainstem implants (BS-ABI) and subsequently presented with bilateral cerebrospinal fluid (CSF) leaks unresponsive to standard treatments. To propose a novel rigid retrosigmoid cranioplasty for treating and preventing CSF leaks in children at high risk for this complication. PATIENT: A 3.5-year-old child with CND, vertebral defects, anal atresia, cardiac defects, tracheo-esophageal fistula, renal anomalies, and limb abnormalities, coloboma, heart defect, atresia choanae, retarded growth and development, genital abnormality, and ear abnormality, Arnold Chiari malformation, previous treated tracheo-esophageal fistula underwent BS-ABI. Postoperatively, the child had recurrent bilateral retroauricular fluid collections. A standard revision procedure revealed breaches in the dural closure, migration of the auditory brainstem implantation (ABI) receiver stimulator on both sides and was unsuccessful in stopping the leak. INTERVENTIONS: Bilateral repair with free fat grafting filling the craniectomy space and two absorbable meshes of poly-L-D-lactic (PLDL) acid stabilized with PLDL pins on the surrounding cranium, one to stabilize the fat graft and one to fix the ABI receiver stimulators inside the subperiosteal pockets. MAIN OUTCOME MEASURE: CSF leak recurrence, postoperative computed tomographic (CT) scans, intra- and postoperative simultaneous electrically evoked auditory brainstem responses (EABRs). Subjective and objective assessment of ABI function. RESULTS: No postoperative CSF leaks at 60 days follow-up. EABRs and consistent behavioral responses obtained at initial mapping on both sides. CONCLUSIONS: The use of BS-ABI likely contributed to bilateral CSF leaks requiring revision surgeries in this child. Simultaneous bilateral craniotomies can put patients at risk for CSF leak. A novel cranioplasty technique employed finally proved successful in stopping the CSF leak in this case.

Nervus Intermedius Guides Auditory Brainstem Implant Surgery in Children with Cochlear Nerve Deficiency.

OBJECTIVE: To investigate the anatomic features of the nervus intermedius and cranial nerve VII in children with cochlear nerve deficiency and to verify whether the nervus intermedius can provide an additional landmark to help guide placement of the auditory brainstem implant electrode. STUDY DESIGN: Case series with chart review. SETTING: Tertiary referral center. SUBJECTS AND METHODS: High-definition video was captured during retrosigmoid surgery in 64 children (mean age, 3.91 ± 2.83 years) undergoing auditory brainstem implant placement. These videos were examined with particular reference to the number and variety of nervus intermedius bundles and any associated facial nerve anomalies. RESULTS: Absence of cranial nerves VI, VII, and VIII was observed in 3, 6, and all 64 children, respectively. Fifteen children had several abnormalities of the facial nerve in the cerebellopontine angle. Anatomic identification of the facial nerve and the bundles composing the nervus intermedius was possible in 46 children. In 12 children, identification was possible with the assistance of intraoperative monitoring. The number of bundles composing the nervus intermedius varied from 1 to 6. The nervus intermedius and cranial nerve IX were useful landmarks for identifying the foramen of Luschka of the lateral recess. CONCLUSION: The nervus intermedius provides an additional landmark during auditory brainstem microsurgery since it was identified in all subjects. The nervus intermedius anatomy and its topographic relationship with the neurovascular structures around the foramen of Luschka have been described for the first time in children with cochlear nerve deficiency.

Open set speech perception with auditory brainstem implant?

OBJECTIVE: Only a small percentage of auditory brainstem implant (ABI) recipients treated for neurofibromatosis type 2 (NF2) have proved capable of identifying words using only the sound from the ABI. Recently, the ABI was applied to a series of patients with no cochlear nerve or with cochlear disorders that could not benefit from a cochlear implant (i.e., cochlear nerve aplasia or posttraumatic avulsion) or whose benefit was or would be severely compromised. A significant number of these patients have proven capable of understanding speech, including effortless telephone use. In the present study, a series of psychophysical tests were administered to determine the cause of the difference in performance between tumor (T) and nontumor (NT) ABI patients. STUDY DESIGN: Retrospective case review. SETTING: Tertiary referral center. PATIENTS: Twenty patients with ABIs participated in the investigation. Ten were NF2 patients and 10 NT subjects. Patient ages ranged from 24 to 61 years. Eleven were males and nine females. INTERVENTION: Auditory rehabilitation in auditory disconnection caused by cochlea or cochlear nerve disorders. RESULTS: There was a significant correlation between modulation detection thresholds and speech understanding and a significant difference in modulation detection between T and NT patients. CONCLUSIONS: The difference in modulation detection between the two groups suggests a difference in the survival of specific cells in the cochlear nucleus that support modulation. The pattern of results indicates a separate pathway of auditory processing that is specialized for modulated sounds, and that pathway is critical for speech understanding. In NF2 patients, the tumor and surgery may selectively damage this pathway, resulting in poor speech recognition with prosthetic stimulation.

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.

Is the middle fossa approach the treatment of choice for intracanalicular vestibular schwannoma?

OBJECTIVES: To compare the 2 surgical techniques most commonly used during vestibular schwannoma (VS) surgery, i.e., the middle fossa (MF) and the retrosigmoid-transmeatal (RS-TM) routes, when hearing preservation is attempted. STUDY DESIGN: A longitudinal study of a series of consecutive patients operated on with the 2 techniques by the same surgeon was conducted. Selection criteria included tumor confined to the internal auditory canal (IAC) with a length ranging from 4 to 12 mm and hearing class A or B. Patients were alternately assigned to 1 of the 2 groups regardless of auditory class and distance of the tumor from the IAC fundus. Thirty-five subjects were operated on with the RS-TM technique and 35 via the MF route. RESULTS: No significant differences in auditory and facial nerve function results between the 2 techniques were observed. The RS-TM approach, however, showed better facial nerve results at discharge. VS size, IAC enlargement, and, particularly, the distance from the IAC fundus were found to influence the postoperative results more than the type of approach itself. CONCLUSIONS: The MF approach has been described as being the better technique for VS surgery in terms of auditory results. However, this claim lacks statistical substantiation because no prospective studies are to be found in the literature. The present longitudinal investigation shows that the MF approach does not afford any particular advantages over the RS-TM route in terms of auditory results in intracanalicular VS, with the exception of tumors reaching the IAC fundus.

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.

Middle fossa versus retrosigmoid-transmeatal approach in vestibular schwannoma surgery: a prospective study.

OBJECTIVE: To compare the advantages, disadvantages, and results obtained with the middle fossa and retrosigmoid-transmeatal approaches during pure intracanalar vestibular schwannoma surgery in an attempt to preserve hearing. STUDY DESIGN: Prospective study of patients treated from 1998 to 2001. SETTING: Tertiary care referral center. PATIENTS: Patients with intracanalar vestibular schwannoma (size ranging from 4 to 12 mm), 25 operated on with the retrosigmoid-transmeatal technique and 25 via the middle fossa route. MAIN OUTCOME MEASURES: Facial nerve and auditory function were examined at 1 year with both techniques. Auditory results were also evaluated as a function of tumor size, distance from the internal auditory canal fundus, and internal auditory canal enlargement. RESULTS: The results indicated no significant difference in facial nerve and auditory function results between the two techniques. The retrosigmoid-transmeatal approach, however, yielded better facial nerve function results at discharge. Postoperative hearing was better when the distance from the fundus was greater than 3 mm, when the size of the vestibular schwannoma was equal to or less than 7 mm, and when the internal auditory canal enlargement was less than 3 mm. CONCLUSIONS: The middle fossa approach does not afford any particular advantages over the retrosigmoid-transmeatal approach in terms of auditory results. Facial nerve function is less satisfactory in the short term, when the middle fossa route is used, but can be improved by decompression and gentle displacement of the facial nerve in its labyrinthine portion.

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.

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.

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.

Improved outcomes in auditory brainstem implantation with the use of near-field electrical compound action potentials.

OBJECTIVE: To compare the outcomes (auditory threshold and open-set speech perception at 48-month follow-up) of a new near-field monitoring procedure, electrical compound action potential, on positioning the auditory brainstem implant electrode array on the surface of the cochlear nuclei versus the traditional far-field electrical auditory brainstem response. STUDY DESIGN: Retrospective study. SETTING: Tertiary referral center. SUBJECTS AND METHODS: Among the 202 patients with auditory brainstem implants fitted and monitored with electrical auditory brainstem response during implant fitting, 9 also underwent electrical compound action potential recording. These subjects were matched retrospectively with a control group of 9 patients in whom only the electrical auditory brainstem response was recorded. Electrical compound action potentials were obtained using a cotton-wick recording electrode located near the surface of the cochlear nuclei and on several cranial nerves. RESULTS: Significantly lower potential thresholds were observed with the recording electrode located on the cochlear nuclei surface compared with the electrical auditory brainstem response (104.4 ± 32.5 vs 158.9 ± 24.2, P = .0030). Electrical brainstem response and compound action potentials identified effects on the neighboring cranial nerves on 3.2 ± 2.4 and 7.8 ± 3.2 electrodes, respectively (P = .0034). Open-set speech perception outcomes at 48-month follow-up had improved significantly in the near- versus far-field recording groups (78.9% versus 56.7%; P = .0051). CONCLUSIONS: Electrical compound action potentials during auditory brainstem implantation significantly improved the definition of the potential threshold and the number of auditory and extra-auditory waves generated. It led to the best coupling between the electrode array and cochlear nuclei, significantly improving the overall open-set speech perception.

The Therapeutic Dilemma of Cochlear Nerve Deficiency: Cochlear or Brainstem Implantation?

OBJECTIVE: To compare the outcomes between 2 age-matched cohorts of children with cochlear nerve deficiency: those receiving auditory brainstem implants (group A) or cochlear implants (group B). STUDY DESIGN: Retrospective cohort study. SETTING: Tertiary referral center. SUBJECTS AND METHODS: Subjects were selected from a pool of 537 children fitted with cochlear implants (n = 443) or auditory brainstem implants (n = 94) over the past 14 years. Performance, examined with the Category of Auditory Performance scale, and complications were compared with a mean follow-up of 5 years. RESULTS: All children had bilateral profound sensorineural hearing loss and cochlear nerve deficiency. Magnetic resonance imaging documented an absent cochlear nerve (n = 12) and a small cochlear nerve (n = 8) in group A and an absent cochlear nerve (n = 11) and a small cochlear nerve (n = 9) in group B (P = 1.000). Children with cochlear implants had Category of Auditory Performance scores spanning from 0 to 3 levels of performance, and all required manual communication mode and visual supplementation. Children with auditory brainstem implants had Category of Auditory Performance scores spanning from 2 to 7, and most patients demonstrated behavioral responses irrespective of inner ear malformations and an absent cochlear nerve or small cochlear nerve (P < .001). CONCLUSIONS: In children with cochlear nerve deficiency, patients fitted with cochlear implants did not develop speech understanding and production. Those fitted with auditory brainstem implants had the opportunity to develop open-set speech perception, acquiring verbal language competence using oral communication exclusively and participating in mainstream education. The overall complication rate of auditory brainstem implants was not greater than that of cochlear implants.