Faculty Bibliography

OBJECTIVE: To evaluate and compare image quality between flat-panel volumetric computed tomography (fpVCT) and multislice CT (msCT) in temporal bones with cochlear implants (CIs), and to evaluate fpVCT imaging for accuracy in determining CI electrode positioning. METHODS: Six cadaveric temporal bones were imaged prior to CI using fpVCT. Each bone was implanted with an electrode array and rescanned in order to create radial reformatted images through each electrode contact. Electrode-modiolar interval (EMI) distances were measured. The bones were fixed and cut in order to grossly evaluate for CI intrascalar positioning and insertional trauma. MAIN OUTCOME MEASURE: To compare image quality between fpVCT and msCT in temporal bones with CI, and to evaluate the utility of fpVCT in post-implantation temporal bone analysis. RESULTS: The mean EMI distances did not differ significantly between fpVCT and msCT images, while the image quality was significantly better for fpVCT. Furthermore, information about intracochlear trauma and intrascalar electrode array positioning can be ascertained using this radiographic technique. CONCLUSION: fpVCT and msCT do not differ significantly in the evaluation of EMI distances in implanted temporal bones, but the image quality is significantly better using fpVCT. Additionally, useful information regarding intracochlear trauma, electrode depth of insertion, and intrascalar positioning can be gained from fpVCT imaging. Given the ease of use, superior image quality, improved convenience, reduced levels of radiation, and agreement with histology, fpVCT is a valuable option for post-implantation temporal bone imaging

OBJECT: The aim of this study was to determine whether patients with neurofibromatosis Type 2 (NF2) who have intact ipsilateral cochlear nerves can have open-set speech discrimination following cochlear implantation. METHODS: Records of 7 patients with documented NF2 were reviewed to determine speech discrimination outcomes following cochlear implantation. Outcomes were measured using consonant-nucleus-consonant words and phonemes; Hearing in Noise Test sentences in quiet; and City University of New York sentences in quiet and in noise. RESULTS: Preoperatively, none of the patients had open-set speech discrimination. Five of the 7 patients had previously undergone excision of ipsilateral vestibular schwannoma (VS). One of the patients who received a cochlear implant had received radiation therapy for ipsilateral VS, and another was undergoing observation for a small ipsilateral VS. Following cochlear implantation, 4 of 7 patients with NF2 had open-set speech discrimination following cochlear implantation during extended follow-up (15-120 months). Two of the 3 patients without open-set speech understanding had a prolonged period between ipsilateral VS resection and cochlear implantation (120 and 132 months), and had cochlear ossification at the time of implantation. The other patient without open-set speech understanding had good contralateral hearing at the time of cochlear implantation. Despite these findings, 6 of the 7 patients were daily users of their cochlear implants, and the seventh is an occasional user, indicating that all of the patients subjectively gained some benefit from their implants. CONCLUSIONS: Cochlear implantation can provide long-term auditory rehabilitation, with open-set speech discrimination for patients with NF2 who have intact ipsilateral cochlear nerves. Factors that can affect implant performance include the following: 1) a prolonged time between VS resection and implantation; and 2) cochlear ossification

Extracochlear electrode extrusion is a potentially under-recognized complication of cochlear implantation. As the age of implantation becomes younger, electrode extrusion is of concern due to future skull growth. Extrusion of several electrodes may compromise performance and thus require surgical reinsertion of the electrodes. Almost 60% of patients with electrode extrusion have required revision surgery. This paper presents a case report and literature review which discusses factors which contribute to electrode extrusion and emphasizes the need for a high degree of suspicion in certain situations. Surgical steps such as electrode fixation techniques are highlighted in order to attempt to reduce the occurrence of this complication

OBJECTIVE: Multi-centre collaborative study to develop and refine the design of a prototype thin perimodiolar cochlear implant electrode array and to assess feasibility for use in human subjects. STUDY DESIGN: Multi-centre temporal bone insertion studies. MATERIALS AND METHODS: The modiolar research array (MRA) is a thin pre-curved electrode that is held straight for initial insertion with an external sheath rather than an internal stylet. Between November 2006 and February 2009, six iterations of electrode design were studied in 21 separate insertion studies in which 140 electrode insertions were performed in 85 human temporal bones by 12 surgeons. These studies aimed at addressing four fundamental questions related to the electrode concept, being: (1) Could a sheath result in additional intra-cochlear trauma? (2) Could a sheath accommodate variations in cochlea size and anatomies? (3) Could a sheath be inserted via the round window? and (4) Could a sheath be safely removed once the electrode had been inserted? These questions were investigated within these studies using a number of evaluation techniques, including X-ray and microfluoroscopy, acrylic fixation and temporal bone histologic sectioning, temporal bone microdissection of cochlear structures with electrode visualization, rotational tomography, and insertion force analysis. RESULTS: Frequent examples of electrode rotation and tip fold-over were demonstrated with the initial designs. This was typically caused by excessive curvature of the electrode tip, and also difficulty in handling of the electrode and sheath. The degree of tip curvature was progressively relaxed in subsequent versions with a corresponding reduction in the frequency of tip fold-over. Modifications to the sheath facilitated electrode insertion and sheath removal. Insertion studies with the final MRA design demonstrated minimal trauma, excellent perimodiolar placement, and very small electrode dimensions within scala tympani. Force measurements in temporal bones demonstrated negligible force on cochlear structures with angular insertion depths of between 390 and 450 degrees . CONCLUSION: The MRA is a novel, very thin perimodiolar prototype electrode array that has been developed using a systematic collaborative approach. The different evaluation techniques employed by the investigators contributed to the early identification of issues and generation of solutions. Regarding the four fundamental questions related to the electrode concept, the studies demonstrated that (1) the sheath did not result in additional intra-cochlear trauma; (2) the sheath could accommodate variations in cochlea size and anatomies; (3) the sheath was more successfully inserted via a cochleostomy than via the round window; and (4) the sheath could be safely removed once the electrode had been inserted

OBJECTIVES/HYPOTHESIS:: Medulloblastoma is the most common pediatric malignant tumor of the central nervous system in children. Treatment includes surgical excision, external beam radiation, and multiagent chemotherapy. Otologic sequelae are common and may result from radiation and/or chemotherapy. Profound sensorineural hearing loss (SNHL) is a known complication of neuro-oncologic treatment and may render these patients eligible for cochlear implantation (CI). Issues of CI in this population, including diagnosis, treatment of preoperative middle ear disease, operative and postoperative course, performance data, and long-term tumor surveillance are highlighted and reviewed. STUDY DESIGN:: Retrospective chart review. METHODS:: Three patients treated for pediatric medulloblastoma with surgical resection, postoperative hyperfractioned craniospinal radiotherapy, and multiagent adjuvant chemotherapy who underwent cochlear implantation were identified. Details of neuro-oncologic treatment and associated otologic complications are presented and analyzed. Primary outcome assessment includes treatment of middle ear pathology, perioperative cochlear implant course, and postimplantation performance data. RESULTS:: Each patient required surgical treatment of chronic ear disease 4 to 16 years after chemoradiation. All progressed to profound SNHL and were implanted 8 to 17 years post-neuro-oncologic treatment. There were no intraoperative complications, and full insertion of the cochlear implant electrode array was achieved in each patient. One patient developed postoperative wound dehiscence requiring operative closure. Postimplantation performance data support significant benefit in all patients. CONCLUSIONS:: Patients treated for pediatric medulloblastoma develop otologic sequelae, including profound SNHL, and may require cochlear implantation. Successful management of middle ear and mastoid pathology involves consideration of potential future cochlear implantation. Postoperative performance data supports cochlear implantation in this population. Laryngoscope, 2009

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

Since the advent of cochlear implantation, candidacy criteria have slowly broadened to include increasingly younger patients. Spurred by evidence demonstrating both perioperative safety and significantly increased speech and language benefit with early auditory intervention, children younger than 12 months of age are now being successfully implanted at many centers. This review highlights the unique challenges involved in cochlear implantation in the very young child, specifically diagnosis and certainty of testing, anesthetic risk, surgical technique, intraoperative testing and postoperative programming, long-term safety, development of receptive and expressive language, and outcomes of speech perception. Overall, the current body of literature indicates that cochlear implantation prior to 1 year of age is both safe and efficacious

HYPOTHESIS: Robotic insertions of actively steerable perimodiolar electrode arrays can substantially reduce insertion forces and prevent electrode buckling. BACKGROUND: Perimodiolar electrodes have been proven to be effective in reducing insertion forces. However, the dedicated techniques of atraumatic electrode insertion require intensive surgeon training. Although some specialized medical robots have been developed to help surgeons in certain minimally invasive surgeries, none are applicable to electrode insertions. METHODS: A robot prototype capable of automatically inserting novel steerable electrode array and adjusting its approach angle toward the scala tympani has been constructed and tested. Comparisons of insertion forces using robotically assisted steerable and straight electrodes on scala tympani models are presented. Simulations and experiments are conducted to compare the robotic insertion outcomes and insertion forces. RESULTS: The use of robotically assisted steerable electrodes for insertions significantly reduces the insertion forces compared with straight electrodes. Based on the results from the experiments, a second-generation robot with insertion force-sensing capability and haptic control to be used in the operating room has been designed for cochlear implant surgery. CONCLUSION: Preliminary experimental results using robot-assisted steerable electrode prototype show that it is effective in reducing insertion forces and preventing electrode buckling. A second-generation robot has been designed and constructed for cochlear implant surgery under operating room conditions

Electrode insertion is the most important step in cochlear implant (CI) surgery. Optimal electrode placement is a prerequisite for maximizing CI success. This article describes CI electrode insertion in the normal and abnormal cochlea, including technical considerations unique to cochlear malformations, dysplasia, ossification, and revision implantation. Currently available electrodes and device specific operative techniques are reviewed. 2010 Elsevier Inc