William H. Shapiro

Threshold, comfortable level and impedance changes as a function of electrode-modiolar distance.

Objective The study investigated the hypothesis that threshold and comfortable levels recorded from cochlear implant patients would reduce, and dynamic range increase, as distance of the electrode from the modiolar wall (radial distance) decreases. Two groups of cochlear implant patients participated; one group using the Nucleus® 24 Contour™ electrode array, and one group using the Nucleus standard straight (banded) array. The Nucleus 24 Contour array has been shown in temporal bone studies to lie closer to the modiolus than the banded array. The relationship of electrode impedance and radial distance is also investigated. Design The study, conducted at three centers, evaluated 21 patients using the Contour array, and 36 patients using the banded array. For each patient, threshold, comfortable levels and dynamic range were measured at four time points. Common ground electrode impedance was recorded clinically from each patient, at time intervals up to 12 wk. An estimate of the radial distance of the electrode from the modiolus was made by analysis of Cochlear view x-rays. Results Threshold and comfortable levels were significantly lower for the Nucleus 24 Contour array than for the banded array. However, dynamic range measurements did not show the predicted increase. In a majority of subjects, a significant correlation was found between the estimated radial distance of the electrode from the modiolus and the measured threshold and comfortable levels. This trend was not observed for dynamic range. The analysis indicates that other factors than radial distance are involved in the resultant psychophysical levels. Clinical impedance measures (common ground) were found to be significantly higher for the Contour array. However, the electrodes on the Contour array are half-rings, which are approximately only half the geometric size of the full rings as electrodes of the standard array. When the geometric electrode area in the two array designs are normalized, the trends in the electrode impedance behavior are similar. Conclusions The results support the hypothesis that the relationship between the radial distance of the electrode and the psychophysical measures are influenced by patterns of fibrous tissue growth and individual patient differences, such as etiology and neural survival. Impedance measures for the Nucleus 24 Contour electrode array were higher than the banded electrode array, but this is primarily due to the reduction in electrode surface area. The different outcomes in impedance over time suggest differences in the relative contributions of the components of impedance with the two arrays.

Cochlear Reimplantation: Surgical Techniques and Functional Results

Objectives/Hypothesis The most common indication for cochlear reimplantation is device failure. Other, less frequent indications consist of “upgrades” (e.g., single to multichannel), infection, and flap breakdown. Although the percentage of failures has decreased over time, an occasional patient requires reimplantation because of device malfunction. The varying designs of internal receiver/stimulators and electrode arrays mandate an examination of the nature and effects of reimplantation for the individual designs. The purpose of the current study was to investigate the reimplantation of several implant designs and to determine whether differences in surgical technique, anatomical findings, and postoperative performance exist.

Use of a multichannel cochlear implant in the congenitally and prelingually deaf population

Fourteen children and three adults, each congenitally and prelinguistically deaf, received the Nucleus® multichannel implant. All underwent extensive evaluations and rehabilitation. The surgery was uneventful, and no patients have been lost to follow‐up.

The benefits of cochlear implantation in the geriatric population.

The deterioration of speech-understanding abilities in the aged that results from factors such as reduced speed and accuracy in processing has been well documented. The purpose of this study was to evaluate whether the geriatric population could benefit from a cochlear implant, despite the possibility of reduced processing abilities. Twenty patients, ages 65 to 85 years, with bilateral profound sensorineural hearing loss received the Nucleus multichannel cochlear prosthesis at NYU Medical Center. All patients underwent extensive preoperative medical and audiologic assessments to determine candidacy. The surgical procedure was well-tolerated by all patients. Mean postoperative test results revealed significant improvements in both auditory performance and quality of life as a result of implant usage. These data support the concept that although a reduction in the processing of sensory stimulation might exist, the elderly can process a new auditory code delivered by means of a cochlear implant.

Neural response telemetry in 12- to 24-month-old children.

The minimum age for cochlear implantation has been reduced to 12 months in an effort to provide auditory stimulation to children with hearing loss during early development. Because behavioral measures in such young children are limited, objective measures such as the electrically evoked compound action potential (EAP) from the auditory nerve are needed to facilitate measurement of stimulation level requirements. We assessed EAPs recorded by the Nucleus 24 neural response telemetry (NRT) system in children who underwent implantation between 12 and 24 months of age. We recorded EAPs in 37 such children (mean age at implantation, 18.1 ± 3.6 months). The EAPs were of large amplitude, and thresholds fell between behavioral T and C levels. A correction factor applied to EAP thresholds provided useful predictions of T levels. The EAPs can be used to ensure that even very young children receive auditory stimulation with their cochlear implants upon device activation.

Auditory Brainstem Implantation in Patients with Neurofibromatosis Type 2

Objectives: Multichannel auditory brainstem implants (ABI) are currently indicated for patients with neurofibromatosis type II (NF2) and schwannomas involving the internal auditory canal (IAC) or cerebellopontine angle (CPA), regardless of hearing loss (HL). The implant is usually placed in the lateral recess of the fourth ventricle at the time of tumor resection to stimulate the cochlear nucleus. This study aims to review the surgical and audiologic outcomes in 18 patients implanted by our Skull Base Surgery Team from 1994 through 2003.

Remote intraoperative monitoring during cochlear implant surgery is feasible and efficient.

Objectives: Intraoperative testing of cochlear implant devices, establishment of electrical threshold for acoustic reflex, and recording neural responses to electrical stimulation have traditionally required the presence of a cochlear implant audiologist in the operating room. The goal of this study was to determine the feasibility of remote testing to improve time efficiency and reduce cost. Study Design: Prospective. Methods: A standard PC with Tridia VNC software and either Cochlear Corporation or Advanced Bionics Corporation mapping software was configured to perform remote testing. The time required to perform on-site or remote testing was measured. Results: With the availability of the laptop and internet access, there were no geographic restrictions regarding the site of remote testing. Remote testing was time efficient, requiring 9 minutes of audiologists time compared with 93 minutes when the audiologist had to travel to the operating room. Conclusion: Remote testing of the cochlear implant device and patients response to electrical stimulation is technically feasible. It is timesaving, practical, and cost efficient.

An evidence-based algorithm for intraoperative monitoring during cochlear implantation.

Objective To generate an evidence-based algorithm for the use of intraoperative testing during cochlear implantation (CI). Study Design Retrospective review. Setting Tertiary referral center. Patients A total of 277 children (aged 6 mo to 17 yr) and adults 18 years and older with normal cochlear anatomy who underwent primary and revision cochlear implantation at a single center between 2005 and 2010 were included. Intervention Intraoperative electrophysiologic monitoring and intraoperative Stenver’s view plain film radiography. Main Outcome Measure Intraoperative testing included the following: 1) individual electrode impedance measurements; 2) neural response telemetry (tNRT) levels for electrodes E20, E15, E10, and E5; and 3) plain film radiograph assessment of electrode position. Results No patient demonstrated abnormalities on all 3 modalities. Open or short electrodes on impedance testing were found in 6% of patients; half of these normalized when remeasured. Absent tNRT responses on 1 or more electrodes occurred in 14% of patients, although complete lack of response was rare (1.4%) and did not correlate with a dysfunctional device. Spread of excitation was performed in 1 patient and was consistent with a tip rollover. Intraoperative radiography identified tip-rollover and extracochlear electrode placement in all cases (n = 5, 1.8%) and prompted the use of the backup device. Conclusion Immediate intraoperative determination of device functionality and optimal electrode placement is advantageous. Of the modalities tested, including electrode impedance, tNRT, and plain radiograph, only the radiographic results impacted intraoperative surgical decision making and led to the use of the backup device.

The effects of residual hearing in traditional cochlear implant candidates after implantation with a conventional electrode.

Objective To analyze the effects of residual hearing on postoperative speech performance in traditional cochlear implant (CI) patients implanted with a conventional electrode. Study Design Retrospective review. Setting Academic tertiary referral center. Patients A total of 129 adults implanted by a single surgeon at a tertiary care facility between June 2005 and November 2010 with measurable preoperative pure tone thresholds at any frequency were included. Intervention Cochlear implantation with a conventional electrode via an anterior inferior cochleostomy. Main Outcome Measure Speech perception using monosyllabic word scores in quiet and sentences in quiet and noise in the electric (CI-only) condition of the implanted ear. Preservation of hearing was defined as complete for postoperative thresholds within 10 dB of preimplant values and partial if greater than 11 dB. Pure tone audiometry and speech perception testing were performed preoperatively and at regular intervals postoperatively, with the 1-year evaluation being the final outcome period. Results Preservation at any frequency or level was not a factor in speech perception outcome, although preservation was more common in low frequencies. Hearing preservation was correlated with younger age at implantation, but was not related to length of hearing loss, cause of deafness, device type, sex, preoperative speech performance, or low-frequency pure-tone average. Conclusion Hearing can be preserved in traditional CI patients implanted with a conventional electrode. Although preservation of hearing may have implications for future technology, it is not currently correlated with speech performance in the CI-only condition.

Intraoperative neural response telemetry as a predictor of performance.

Objective: To determine whether intraoperative neural response telemetry (tNRT) is predictive of postoperative speech perception. Study Design: Retrospective review. Setting: Tertiary referral center. Patients: Children (n = 24) aged between 5 and 17 years and adults 18 years and older (n = 73) with severe-to-profound hearing loss and implanted with the Nucleus Freedom device between 2005 and 2008 and observed at least 1 year were included. Intervention: Intraoperative neural response telemetry after insertion of the electrode array. Main Outcome Measure: Measures included 1) intraoperative tNRT measurements and 2) preoperative and 1-year postoperative open-set word recognition scores using age-appropriate open-set tests for children and adults. Intraoperative neural response telemetry levels for electrodes E20, E15, E10, and E5 in each patient were correlated to performance at the 1-year evaluation interval. Results: No correlation existed between tNRT responses and open-set speech performance at the 1-year evaluation. Several patients had absent tNRT in the OR but developed speech recognition abilities, whereas the remaining patients had intraoperative responses with levels of postoperative performance ranging from 0% to 100%. Conclusion: This study suggests that there is no significant correlation between intraoperative tNRT and speech perception performance at 1 year. At the time of surgery, tNRT provides valuable information regarding the electrical output of the implant and the response of the auditory system to electrical stimulation and preliminary device programming data; however, it is not a valuable predictor of postoperative performance. Furthermore, the absence of tNRT does not necessarily indicate a lack of stimulation.