Faculty Bibliography

OBJECTIVES: As a result of universal newborn hearing screening and improved evaluation tools, many children with severe to profound hearing loss are being diagnosed as infants. This affords the opportunity to provide these children access to cochlear implantation, although medical and audiologic challenges must be addressed. The purpose of this study was to investigate the safety and efficacy of cochlear implantation in children who are younger than 1 year. METHODS: A prospective study was conducted of 18 children who had confirmed severe to profound sensorineural hearing loss and received cochlear implants at our medical center before 12 months of age. The length of device usage ranged from 6 months to 4 years, 5 months. The main outcomes measured were perioperative and postoperative surgical/medical aspects, the Infant-Toddler Meaningful Auditory Integration Scale and age-appropriate phoneme, and word and sentence recognition tests, when appropriate. RESULTS: All children had full insertions of the electrode array without surgical complications and are developing age-appropriate auditory perception and oral language skills. CONCLUSIONS: Early implantation is feasible and beneficial in some children who are younger than 12 months and should be considered with attention to variables involved in the decision-making process, including possible increased surgical risk, skull size and scalp thickness, and mastoid development

OBJECTIVES AND HYPOTHESIS: This study has the specific aim of evaluating the insertion characteristics of a new cochlear implant electrode. Techniques for evaluation of fluoroscopic real time mechanical insertion dynamics, histologic electrode position and trauma results, hydraulic force, and mechanical insertion forces are presented. In addition, this study should serve to present a novel model for cochlear implant electrode insertion evaluations. STUDY DESIGN: Prospective analysis using a series of analytical techniques. METHODS: All studies are conducted in fixed cadaveric temporal bones. Real time fluoroscopic insertion evaluations, histologic evaluations for trauma and electrode position in embedded bones, hydraulic measures, and mechanical intracochlear force measurements are conducted with a current and new electrode. RESULTS: The Contour Advance electrode provides a more reliable and less traumatic insertion when deployed with the Advance Off Stylet technique. This is largely because of a reduction in intracochlear outer wall force generation. Fluoroscopic and histologic analysis reveal a smooth insertion without reliance on cochlear outer wall contact. No hydraulic forces were detected when measured from the superior semicircular canal ampulla. CONCLUSION: The model used for this study provides valuable information to cochlear implant surgeons and design engineers. The Contour Advance electrode, inserted with the Advance Off Stylet technique, represents an improvement over the Contour electrode inserted with the standard insertion technique

In recent years, new designs of cochlear implant electrodes have been introduced in an attempt to improve efficiency and performance by locating stimulation sites closer to spiral ganglion neurons and deeper into the scala tympani. The goal of this study was to document insertion depth, intracochlear position and insertion trauma with the Nucleus Contour electrode and to compare results to those observed with the earlier generation Nucleus banded electrode. For this comparison eight Nuclears banded electrodes and 18 Contour electrodes were implanted in cadaver temporal bones using a realistic surgical exposure. Two experienced cochlear implant surgeons and two otology fellows with specialized training in cochlear implant surgery were selected for the study to represent a range of surgical experience similar to that of surgeons currently performing the procedure throughout the world. Following insertion of the electrodes, specimens were imaged using plain film X-ray, embedded in acrylic resin, cut in radial sections with the electrodes in place, and each cut surface was polished. Insertion depth was measured in digitized X-ray images, and trauma was assessed in each cross-section. The Contour electrode inserted more deeply (mean depth=17.9 mm or 417 degrees ) than the banded electrode (mean depth=15.3 mm or 285 degrees ). The incidence and severity of trauma varied substantially among the temporal bones studied. However, the nature and frequency of injuries observed with the two devices were very similar. The Contour electrode was clearly positioned closer to the modiolus than the banded model, and also appeared easier to use. Based on this difference in position and data from previous studies we conclude that the Contour electrode may provide lower thresholds and improved channel selectivity, but the incidence of trauma remains a problem with the newer design. The relative influences of electrode positioning and neural degeneration that may result from trauma are as yet unclear

Cochlear implant electrode insertion is the most important step in cochlear implant surgery. Optimal placement facilitates optimal results. This article describes cochlear implant electrode insertion techniques in normal and abnormal cochleae and the currently available electrodes

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. STUDY DESIGN: A retrospective chart review of 18 patients with ABIs. METHODS: We evaluated demographic data including age at implantation, number of tumor resections before implantation, tumor size, surgical approach, and postoperative surgical complications. The ABI auditory results at 1 year were then evaluated for number of functioning electrodes and channels, hours per day of use, nonauditory side effect profile and hearing results. Audiologic data including Monosyllable, Spondee, Trochee test (MTS) Word and Stress scores, Northwestern University Children's Perception of Speech (NU-CHIPS), and auditory sensitivity are reported. RESULTS: No surgical complications caused by ABI implantation were revealed. A probe for lateral recess and cochlear nucleus localization was helpful in several patients. A range of auditory performance is reported, and two patients had no auditory perceptions. Electrode paddle migration occurred in two patients. Patient education and encouragement is very important to obtain maximum benefit. CONCLUSIONS: ABIs are safe, do not increase surgical morbidity, and allow most patients to experience improved communication as well as access to environmental sounds. Nonauditory side effects can be minimized by selecting proper stimulation patterns. The ABI continues to be an emerging field for hearing rehabilitation in patients who are deafened by NF2

OBJECTIVES: Cochlear implant device failures and reimplantation have mainly been reported on in adults. The purpose of this study was to isolate precursors of device failures and assess the effects of reimplantation in children. METHODS: From 1997 to 2003, 27 children underwent cochlear reimplantation at our institution. The pre-failure complaints were categorized and correlated with actual failure modes and postimplantation results. Speech-recognition tests were used to evaluate pre- and post-reimplantation performance. RESULTS: Pre-failure length of usage ranged from 0 to 12 years. Symptoms including pain, intermittence, reduced performance, noise and the need for frequent device adjustments were associated with device failures, although not with a particular mode of failure. Post reimplantation performance was equal to but not immediately better than pre-failure results in children who received upgraded devices. CONCLUSIONS: Specific complaints, frequent need for device adjustments and reduced speech recognition can be precursors to device failures, underscoring the need for routine follow-up evaluations. Reimplantation with newer technology does not guarantee improved speech understanding and often requires an adjustment period to reach pre-reimplantation levels.

The purpose of this study was to evaluate the performance of the new features of the Nucleus Research Platform 8 (RP8), a system developed specifically for research purposes The RP8 consists of a research implant, a speech processor and a new NRT software (NRT v4), and includes comparisons of the different artefact-cancellation methods, NRT threshold, and recovery function measurements. The system has new artefact-suppression techniques and new diagnostic capabilities; their performance has been verified in animal experiments. In this study, NRT data were collected from 15 postlingually deafened adult cochlear implant patients intraoperatively and up to 6 months postoperatively after switch-on. The initial investigation in two clinics in Europe focused primarily on the enhanced NRT capabilities Results from the trial in two European clinics indicate that NRT measurements can be obtained with lower noise levels. A comparison of the different artefact-cancellation techniques showed that the forward-masking paradigm implemented in the Nucleus 3 system is still the method of choice. The focus of this report is on recovery function characteristics, which may give insight into auditory nerve fiber properties with regard to higher stimulation rates

OBJECTIVE: Perimodiolar electrode arrays were developed to improve stimulation of specific neural populations and to decrease power consumption. Postoperative radiographs suggest that some arrays are more tightly coiled than others. The purpose of this study was to evaluate whether the degree of modiolar coil correlates with electrical threshold and/or performance measures postimplantation with the Nucleus CI24RCS (Contour) device. STUDY DESIGN: Retrospective review. SETTING: Cochlear implant center and a tertiary care hospital. PATIENTS: Twenty-eight adult cochlear implant recipients with normal cochlear anatomy who underwent implantation with the Nucleus C124RCS perimodiolar electrode and are at least 1 year postimplantation. INTERVENTIONS: Therapeutic. MAIN OUTCOME MEASURES: Radiologic degree of perimodiolar electrode placement (determined by a computer algorithmic analysis) compared with electrical thresholds and standard speech perception outcome measures at 1 year postcochlear implantation. RESULTS: No significant correlations were found between the degree of modiolar coiling of the electrode array and electrical thresholds and speech perception outcome measures at 1 year postcochlear implantation. CONCLUSIONS: The degree of coiling of a modiolar hugging electrode array was not directly correlated with the level of electrical thresholds or postoperative speech perception outcome measures. Appearance of coil tightness on postoperative radiographs could reflect either differences in array placement or intrinsic variations in cochlear anatomy, and variations in speech perception performance can be influenced by other factors, including length of deafness