Craig A. Buchman

Vestibular effects of cochlear implantation.

Objectives/Hypothesis: Cochlear implantation (CI) carries with it the potential risk for vestibular system insult or stimulation with resultant dysfunction. As candidate profiles continue to evolve and with the recent development of bilateral CI, understanding the significance of this risk takes on an increasing importance.

Cochlear implantation in children with auditory neuropathy spectrum disorder

Objective: To report the patients characteristics, preoperative audiological profiles, surgical outcomes, and postoperative performance for children with auditory neuropathy spectrum disorder (ANSD) who ultimately received cochlear implants (CIs). Design: Prospective, longitudinal study of children with ANSD who received CIs after a stepwise management protocol that included electrophysiologic and medical assessment, documentation of behavioral audiometric thresholds and subsequent fitting of amplification according to Desired Sensation Level targets, auditory-based intervention with careful monitoring of skills development and communication milestones, and finally implantation when progress with the use of acoustic amplification was insufficient. Results: Of 140 children with ANSD, 52 (37%) received CIs in their affected ears (mean duration of use of 41 mos). Many of these children were born prematurely (42%) and impacted by a variety of medical comorbidities. More than one third (38%) had abnormal findings on preoperative magnetic resonance imaging of the brain and inner ear, and 81% had a greater than severe (>70 dB HL) degree of hearing loss before implantation. Although 50% of the implanted children with ANSD demonstrated open-set speech perception abilities after implantation, nearly 30% of them with >6 months of implant experience were unable to participate in this type of testing because of their young age or developmental delays. No child with cochlear nerve deficiency (CND) in their implanted ear achieved open-set speech perception abilities. In a subgroup of children, good open-set speech perception skills were associated with robust responses elicited on electrical-evoked intracochlear compound action potential testing when this assessment was possible. Conclusions: This report shows that children with ANSD who receive CIs are a heterogeneous group with a wide variety of impairments. Although many of these children may ultimately benefit from implantation, some will not, presumably because of a lack of electrical-induced neural synchronization, the detrimental effects of their other associated conditions, or a combination of factors. When preoperative magnetic resonance imaging reveals central nervous system pathology, this portends a poor prognosis for the development of open-set speech perception, particularly when CND is evident. These results also show that electrical-evoked intracochlear compound action potential testing may help identify those children who will develop good open-set speech perception. Instead of recommending CI for all children with electrophysiologic evidence of ANSD, the stepwise management procedure described herein allows for the identification of children who may benefit from amplification, those who are appropriate candidates for cochlear implantation, and those who, because of bilateral CND, may not be appropriate candidates for either intervention.

Auditory neuropathy characteristics in children with cochlear nerve deficiency.

Objective: To describe a group of children exhibiting electrophysiologic responses characteristic of auditory neuropathy (AN) who were subsequently identified as having absent or small cochlear nerves (i.e., cochlear nerve deficiency). Design: A retrospective review of the clinical records, audiological testing results, and magnetic resonance imaging (MRI) studies. Fifty-one of 65 children with AN characteristics on auditory brain stem response (ABR) testing had MRI available for review. Nine (18%) of these 51 children with ABR characteristic of AN have been identified as having small (N = 2; 4%) or absent (N = 7; 14%) cochlear nerves on MRI. Results: Of the nine children with cochlear nerve deficiency, five (56%) were affected unilaterally and four (44%) bilaterally. Eight of nine presented after failing a newborn infant hearing screening, whereas one presented at 3 yr of age. On diagnostic ABR testing, all 9 children (9 of 13 affected ears; 69%) had evidence of a cochlear microphonic (CM) and absent neural responses in at least one ear. In the unilateral cases, AN characteristics were detected in all affected ears. In bilateral cases, at least one of the ears in each child demonstrated the AN phenotype, whereas the contralateral ear had no CM identified. Only one ear with cochlear nerve deficiency had present otoacoustic emissions as measured by distortion-product otoacoustic emissions. In children with appropriate available behavioral testing results, all ears without cochlear nerves were identified as having a profound hearing loss. Only 4 (31%) of the 13 ears with cochlear nerve deficiency had a small internal auditory canal on MRI. Conclusions: Children with cochlear nerve deficiency can present with electrophysiologic evidence of AN. These children frequently refer on newborn screening examinations that use ABR-based testing methods. Similar to other causes of AN, diagnostic ABR testing will show a CM with absent neural responses. Given that 9 (18%) of 51 children with available MRI and electrophysiologic characteristics of AN in our program have been identified as having cochlear nerve deficiency makes this a relatively common diagnosis. These findings suggest that MRI is indicated for all children diagnosed with AN. Moreover, electrophysiologic evidence of unilateral AN in association with a profound hearing loss should make the clinician highly suspicious for this problem. Although children with cochlear nerve deficiency who have a small nerve may benefit from cochlear implantation or amplification, these interventions are obviously contraindicated in children with completely absent cochlear nerves.

Cochlear Implantation in Children with Congenital Inner Ear Malformations

Objective/Hypothesis: To assess the audiologic and surgical outcomes for pediatric cochlear implant patients with inner ear malformations.

Multicenter U.S. bilateral MED-EL cochlear implantation study: Speech perception over the first year of use

Objective: Binaural hearing has been shown to support better speech perception in normal-hearing listeners than can be achieved with monaural stimulus presentation, particularly under noisy listening conditions. The purpose of this study was to evaluate whether bilateral electrical stimulation could confer similar benefits for cochlear implant listeners. Design: A total of 26 postlingually deafened adult patients with short duration of deafness were implanted at five centers and followed up for 1 yr. Subjects received MED-EL COMBI 40+ devices bilaterally; in all but one case, implantation was performed in a single-stage surgery. Speech perception testing included CNC words in quiet and CUNY sentences in noise. Target speech was presented at the midline (0 degrees), and masking noise, when present, was presented at one of three simulated source locations along the azimuth (−90, 0, and +90 degrees). Results: Benefits of bilateral electrical stimulation were observed under conditions in which the speech and masker were spatially coincident and conditions in which they were spatially separated. Both the “head shadow” and “summation” effects were evident from the outset. Benefits consistent with “binaural squelch” were not reliably observed until 1 yr after implantation. Conclusions: These results support a growing consensus that bilateral implantation provides functional benefits beyond those of unilateral implantation. Longitudinal data suggest that some aspects of binaural processing continue to develop up to 1 yr after implantation. The squelch effect, often reported as absent or rare in previous studies of bilateral cochlear implantation, was present for most subjects at the 1 yr measurement interval.

Nasal and otologic effects of experimental influenza A virus infection.

Past studies showed that experimental rhinovirus colds in adults resulted in eustachian tube dysfunction and abnormal middle ear pressures. In the present study, the symptoms and pathophysiologic findings accompanying experimental influenza viral infection were documented. A total of 33 healthy adult volunteers were intranasally challenged with an influenza A/Kawasaki/86 (H1N1) virus and cloistered over a 9-day postchallenge period to monitor for evidence of infection, signs and symptoms of illness, and the extent and frequency of pathophysiologic responses of the nose, eustachian tube, and middle ear. Results showed a protective effect of high (≥16) prechallenge specific hemagglutination-inhibition antibody titer on the rate of infection and the magnitude and extent of provoked symptoms and pathophysiologic findings. Infected subjects with low (<16) prechallenge serum antibody titers (n = 21) developed significant respiratory illness. These subjects also had objectively measurable increases in nasal secretion production, and decreased nasal patency and mucociliary clearance rates. More than 80% of the infected subjects developed eustachian tube dysfunction, and approximately 80% had middle ear underpressures of less than −100 mm H2O on study days 4 and 5. Five of 21 infected subjects with low prechallenge antibody titers had otoscopic evidence of otitis media with effusion. These results support a causal role for viral upper respiratory tract infection in the pathogenesis of otitis media, possibly mediated by the early development of eustachian tube dysfunction and abnormal middle ear pressure.

Internal auditory canal morphology in children with cochlear nerve deficiency

Objective: To describe the internal auditory canal (IAC) and inner ear morphologic characteristics of children with cochlear nerve (CN) deficiency. Study Design: Retrospective case series. Setting: Tertiary referral center. Patients: Fourteen children with small or absent (deficient) CNs have been identified by means of high-resolution magnetic resonance imaging (MRI). Interventions: MRI of the brain. Clinical evaluation. Main Outcome Measures: Review of medical records, audiological testing results, and imaging studies. Images were evaluated for the structure of the cochlear, vestibular and facial nerves, IACs and inner ears. Audiometric thresholds were evaluated in all subjects. Methods: Fourteen children with small or absent (deficient) CNs have been identified by means of high-resolution MRI. A review of the medical records, audiologic testing results, and imaging studies was undertaken. The images were evaluated for the structure of the cochlear, vestibular and facial nerves, IACs, and inner ears. The audiometric thresholds were evaluated in all subjects. Results: Among the 14 patients, 5 had known syndromes. MRI allowed an exact specification of the nervous structures within all ears with normal-size IACs. Precise characterization of the nerves in ears with small IACs was more difficult, requiring a consideration of both imaging findings and functional parameters. Five children had bilateral deficient CNs, whereas the remaining 9 subjects were affected unilaterally. Thus, 19 ears had CN deficiency (absent CN, 16; small CN, 3). Eleven ears had normal-size IACs and deficient CNs. Of the 9 ears with small IACs, 8 had deficient CNs (absent, 7; small, 1) on the basis of both MRI and functional assessments. Two ears with small IACs had clear morphologic and/or functional evidence for the presence of a CN: one had a small-size CN on MRI, whereas another had a single nerve in a small IAC with present facial and auditory functions. Conclusion: The findings of this study suggest that CN deficiency is not an uncommon cause of congenital hearing loss. The findings that most ears with CN deficiency had normal IAC morphology and that two ears with small IACs had CNs present indicate that IAC morphology is an unreliable surrogate marker of CN integrity. On the basis of these findings, we think that high-resolution MRI, rather than CT imaging, should be performed in all cases of pediatric hearing loss, especially in those cases where profound hearing loss has been documented. For ears with small IACs, the resolution of MRI currently remains limiting. In these cases, the determination of CN status frequently requires a variety of anatomic (CT and MRI) and functional tests (auditory brainstem response, otoacoustic emissions, behavioral audiometry, and physical examination).

Value of Computed Tomography in the Evaluation of Children With Cochlear Nerve Deficiency

Objective: To assess the predictive value of high-resolution computed tomography (HRCT) in the evaluation of children with cochlear nerve deficiency (CND). Study Design: Retrospective review of medical records. Setting: Tertiary referral center, hospital setting. Patients: Nineteen children (31 ears) with CND. Interventions: Magnetic resonance imaging (MRI), HRCT, and audiologic evaluation. Main Outcome Measures: Comparisons of the morphology of the internal auditory canal (IAC), the bony cochlear nerve canal (BCNC) as seen on HRCT, and audiologic data. Results: Of 12 ears with MRI evidence of an absent cochlear nerve (CN) and a normal-size IAC, all had a patent BCNC as revealed by HRCT. Four of these ears failed auditory stimulation after cochlear implantation, confirming clinically significant CND. Of 15 ears with a narrow IAC and a single nerve visible on MRI, 2 (13.3%) had a normal-size BCNC, 4 (26.7%) were narrow, and 9 (60.0%) were absent. One ear with a narrow IAC, normal BCNC, and a single nerve as revealed by MRI has benefited from cochlear implantation. Conclusion: Using BCNC patency, as revealed by HRCT, as a means of identifying CND would miss all cases of absent CNs in the setting of a normal-size IAC. Thus, MRI should be the primary modality for imaging children with severe to profound sensorineural hearing loss. When MRI demonstrates a single nerve within a narrow IAC, the addition of HRCT can further identify more than half of these cases as involving absent CNs because of an absent BCNC. In a subset of patients, CN status remains indeterminate.

Cochlear implantation with hearing preservation yields significant benefit for speech recognition in complex listening environments

Objective: The aim of this study was to assess the benefit of having preserved acoustic hearing in the implanted ear for speech recognition in complex listening environments. Design: The present study included a within-subjects, repeated-measures design including 21 English-speaking and 17 Polish-speaking cochlear implant (CI) recipients with preserved acoustic hearing in the implanted ear. The patients were implanted with electrodes that varied in insertion depth from 10 to 31 mm. Mean preoperative low-frequency thresholds (average of 125, 250, and 500 Hz) in the implanted ear were 39.3 and 23.4 dB HL for the English- and Polish-speaking participants, respectively. In one condition, speech perception was assessed in an eight-loudspeaker environment in which the speech signals were presented from one loudspeaker and restaurant noise was presented from all loudspeakers. In another condition, the signals were presented in a simulation of a reverberant environment with a reverberation time of 0.6 sec. The response measures included speech reception thresholds (SRTs) and percent correct sentence understanding for two test conditions: CI plus low-frequency hearing in the contralateral ear (bimodal condition) and CI plus low-frequency hearing in both ears (best-aided condition). A subset of six English-speaking listeners were also assessed on measures of interaural time difference thresholds for a 250-Hz signal. Results: Small, but significant, improvements in performance (1.7–2.1 dB and 6–10 percentage points) were found for the best-aided condition versus the bimodal condition. Postoperative thresholds in the implanted ear were correlated with the degree of electric and acoustic stimulation (EAS) benefit for speech recognition in diffuse noise. There was no reliable relationship among measures of audiometric threshold in the implanted ear nor elevation in threshold after surgery and improvement in speech understanding in reverberation. There was a significant correlation between interaural time difference threshold at 250 Hz and EAS-related benefit for the adaptive speech reception threshold. Conclusions: The findings of this study suggest that (1) preserved low-frequency hearing improves speech understanding for CI recipients, (2) testing in complex listening environments, in which binaural timing cues differ for signal and noise, may best demonstrate the value of having two ears with low-frequency acoustic hearing, and (3) preservation of binaural timing cues, although poorer than observed for individuals with normal hearing, is possible after unilateral cochlear implantation with hearing preservation and is associated with EAS benefit. The results of this study demonstrate significant communicative benefit for hearing preservation in the implanted ear and provide support for the expansion of CI criteria to include individuals with low-frequency thresholds in even the normal to near-normal range.

Scala tympani cochleostomy II: topography and histology.

Objective: To assess intracochlear trauma using two different round window‐related cochleostomy techniques in human temporal bones.