Intraoperative electrocochleographic characteristics of auditory neuropathy spectrum disorder in cochlear implant subjects

Auditory neuropathy spectrum disorder (ANSD) is characterized by an apparent discrepancy between measures of cochlear and neural function based on auditory brainstem response (ABR) testing. Clinical indicators of ANSD are a present cochlear microphonic (CM) with small or absent wave V. Many identified ANSD patients have speech impairment severe enough that cochlear implantation (CI) is indicated. To better understand the cochleae identified with ANSD that lead to a CI, we performed intraoperative round window electrocochleography (ECochG) to tone bursts in children (n = 167) and adults (n = 163). Magnitudes of the responses to tones of different frequencies were summed to measure the “total response” (ECochG-TR), a metric often dominated by hair cell activity, and auditory nerve activity was estimated visually from the compound action potential (CAP) and auditory nerve neurophonic (ANN) as a ranked “Nerve Score”. Subjects identified as ANSD (45 ears in children, 3 in adults) had higher values of ECochG-TR than adult and pediatric subjects also receiving CIs not identified as ANSD. However, nerve scores of the ANSD group were similar to the other cohorts, although dominated by the ANN to low frequencies more than in the non-ANSD groups. To high frequencies, the common morphology of ANSD cases was a large CM and summating potential, and small or absent CAP. Common morphologies in other groups were either only a CM, or a combination of CM and CAP. These results indicate that responses to high frequencies, derived primarily from hair cells, are the main source of the CM used to evaluate ANSD in the clinical setting. However, the clinical tests do not capture the wide range of neural activity seen to low frequency sounds

Influence of Age at Revision Cochlear Implantation on Speech Perception Outcomes

IMPORTANCE: This study reviewed whether advanced age should be a consideration when revision cochlear implantation is warranted. OBJECTIVE: To examine whether age at revision cochlear implantation is related to postrevision speech perception performance. DESIGN, SETTING, AND PARTICIPANTS: A retrospective analysis was performed in an academic tertiary care center. Participants included 14 younger adults (<65 years) and 15 older adults (≥65 years) who underwent revision cochlear implantation. INTERVENTION: Revision cochlear implantation. MAIN OUTCOMES AND MEASURES: Speech perception performance, as measured with consonant-nucleus-consonant [CNC] words in quiet, at the best prerevision interval as well as the 3- and 6-month postrevision intervals were compared between the 2 cohorts. The CNC word test consists of 10 lists of 50 phonemically balanced monosyllabic words, scored with a range of 0% to 100% correct. RESULTS: Both cohorts experienced a restoration in speech perception scores after revision cochlear implantation compared with their best performance before the revision (mean [SD] CNC word test scores for the younger cohort: 43.9% [25.6%] before revision and 47.7% [21.3%] at 3 months and 47.6% [19.8%] at 6 months after revision; for the older cohort: 36.3% [19.1%] before revision and 35.3% [17.2%] at 3 months and 39.9% [16.3%] at 6 months after revision; F₂,₅₄= 0.93; P = .40). There was no interaction between age at revision surgery and speech perception performance at each assessment interval (F₂,₅₄= 0.51; P = .60). CONCLUSIONS AND RELEVANCE: In this study, age at revision cochlear implantation was not related to postrevision speech perception performance. Advanced age should not be considered a contraindication to revision cochlear implantation

Long-term Speech Perception in Elderly Cochlear Implant Users

IMPORTANCE: A review of a test battery presented in both quiet and noise may clarify what the progression of speech perception abilities is in older adult cochlear implant users and whether the performance declines with advancing age. OBJECTIVE: To examine whether older adults (≥65 years) with cochlear implants maintain stable speech perception performance after at least 10 years of listening experience with an external speech processor. DESIGN AND SETTING: Retrospective analysis performed in an academic tertiary care center. PARTICIPANTS: Fourteen older adult cochlear implant recipients with at least 10 years of listening experience. MAIN OUTCOME MEASURES: Speech perception outcomes as measured with Consonant-Nucleus-Consonant words in quiet and Hearing in Noise Test sentences in quiet and steady-state noise were analyzed retrospectively at the 6-month and 1-, 5-, and 10-year postoperative follow-up intervals. RESULTS: Consonant-Nucleus-Consonant word scores remained stable between 6 months and 1 year of listening experience, improved significantly (P < .001) between 1 year and 5 years, and remained stable between 5 years and 10 years. Hearing in Noise Test sentence scores in quiet and noise showed a similar pattern, with stability in performance between the 6-month to 1-year and 5-year to 10-year follow-up intervals, and significantly improved performance (P = .04) between the 1-year and 5-year follow-up intervals. CONCLUSIONS AND RELEVANCE: On average, patients who undergo cochlear implantation at age 65 years or older do not experience a decline in speech perception performance with extended listening experience and may potentially continue to see improvements beyond the 1-year follow-up interval

Correlation of Early Auditory Potentials and Intracochlear Electrode Insertion Properties: An Animal Model Featuring Near Real-Time Monitoring

The goal of this work was to assess electrophysiologic response changes to acoustic stimuli as an intracochlear electrode impacted cochlear structures in an animal model of hearing preservation cochlear implantation. The ultimate goal is to develop efficient procedures for assessing the status of cochlear physiology for intraoperative use

Assessment of cochlear synaptopathy by electrocochleography to low frequencies in a preclinical model and human subjects

Cochlear synaptopathy is the loss of synapses between the inner hair cells and the auditory nerve despite survival of sensory hair cells. The findings of extensive cochlear synaptopathy in animals after moderate noise exposures challenged the long-held view that hair cells are the cochlear elements most sensitive to insults that lead to hearing loss. However, cochlear synaptopathy has been difficult to identify in humans. We applied novel algorithms to determine hair cell and neural contributions to electrocochleographic (ECochG) recordings from the round window of animal and human subjects. Gerbils with normal hearing provided training and test sets for a deep learning algorithm to detect the presence of neural responses to low frequency sounds, and an analytic model was used to quantify the proportion of neural and hair cell contributions to the ECochG response. The capacity to detect cochlear synaptopathy was validated in normal hearing and noise-exposed animals by using neurotoxins to reduce or eliminate the neural contributions. When the analytical methods were applied to human surgical subjects with access to the round window, the neural contribution resembled the partial cochlear synaptopathy present after neurotoxin application in animals. This result demonstrates the presence of viable hair cells not connected to auditory nerve fibers in human subjects with substantial hearing loss and indicates that efforts to regenerate nerve fibers may find a ready cochlear substrate for innervation and resumption of function

Flexible cochlear microendoscopy in the gerbil

To validate the scientific utility of flexible cochlear microendoscopy in the gerbil. This model is currently being developed to study the effects of intracochlear electrode positioning on functional parameters

Imaging Characteristics of Children With Auditory Neuropathy Spectrum Disorder

To identify and define the imaging characteristics of children with auditory neuropathy spectrum disorder (ANSD)

Electrophysiological Properties of Cochlear Implantation in the Gerbil Using a Flexible Array

Cochlear implants (CI) perform especially well if residual acoustic hearing is retained and combined with the CI in the same ear (also termed hybrid or electric-acoustic stimulation). However, in most CI patients, residual hearing is at least partially compromised during surgery, and in some it is lost completely. At present, clinicians have no feedback on the functional status of the cochlea during electrode insertion. Development of an intraoperative physiological recording algorithm during electrode insertion could serve to detect reversible cochlear trauma and optimal placement relative to surviving hair cells. In this report, an animal model was used to assist in determining physiological markers for these conditions using a flexible electrode similar to human surgery

Detection of intracochlear damage during cochlear implant electrode insertion using extracochlear measurements in the gerbil

An intraoperative monitoring algorithm during cochlear implant electrode insertion could be used to detect trauma and guide electrode placement relative to surviving hair cells. The aim of this report was to assess the feasibility of using extracochlear recording sites to monitor acoustically evoked responses from surviving hair cells and neural elements during implantation in an animal model

Intracochlear Recordings of Electrophysiologic Parameters Indicating Cochlear Damage

The pathophysiologic mechanisms resulting in hearing loss during electrode implantation are largely unknown. To better understand the functional implications of electrode implantation, we recorded the effects of cochlear damage on acoustically evoked intracochlear measurements using normal-hearing gerbils