Cochlear implant indications

Many centers are investigating the safety and efficacy of cochlear implants in adults and children. In the United States, the Food and Drug Administration (FDA) has monitored these investigations, recently approving two devices for general use in adults. In general, appropriate implant candidates have a bilateral, profound to total sensorineural hearing loss, are unable to benefit from conventional hearing aids, are in good physical and mental health, and have the motivation and patience to complete a rehabilitation program. The patient likely to receive most benefit from a cochlear implant is one who acquires profound deafness after developing verbal language skills and is implanted within a few years of the onset of deafness.     

Cochlear implant histopathology

Twenty-two temporal bones and one brain stem from 13 cochlear implant patients were examined histologically. Sixteen temporal bones had undergone one or more implant procedure. Results of analysis suggested that the ganglion cells were the responding elements to the implant and that useful auditory sensation could result from as few as 10 percent of the normal number of ganglion cells. All implanted bones exhibited varying amounts of fibrosis (some ossified) in the basal turn of the cochlea and beyond in some cases. Usually there was damage to the surviving elements of the organ of Corti and the dendrites throughout the extent of the electrode insertion. However, the ganglion cell population was not affected. Prolonged electrical stimulation (up to 14 years) did not affect ganglion cell survival in three cases, and had no effect on the cochlear nerves in two cases or on cochlear nuclei in one case.     

Cochlear implant programming

Cochlear implants have become a viable treatment option for individuals who present with severe to profound hearing loss. While there are several parameters that affect the successful use of this technology, quality programming of the cochlear implant system is crucial. This review chapter focuses on general device programming techniques, programming techniques specific to children, objective programming techniques, a brief overview of programming parameters of the currently commercially available multichannel systems, and managing patient complaints and device failures. The chapter also provides what the authors believe the future may hold for new programming techniques.     

Cochlear implant histopathology

The microscopic examination of fifty-five serially sectioned implanted temporal bones has provided insight into what is being stimulated; and the changes that are the result of the insertion and presence of the implant. The ganglion cell bodies (neurons) are structures being stimulated (two laboratories have reported an inverse relationship of the number of neurons and performance). Insertion through the round window, verses a cochleostomy, produces the least fibrosis and new bone. Fibrosis and new bone do not affect the implant function unless they form in the scala vestibuli in the region of the ductus reuniens, and, block it; and produce cochlear hydrops resulting in a delayed low tone loss of hearing in hybrid implants. Animal models cannot be applied to humans because of the difference in size and myelination of the neurons.     

Cochlear implant management today

W?hrend Ende der 1970er Jahre Cochlear-Implante in erster Linie das Erkennen und Differenzieren von Umweltger?uschen erm?glichten, ist heute für viele Patienten ein früher kaum für m?glich gehaltenes, offenes Sprachverst?ndnis Realit?t geworden. Eine binaurale Cochlear-Implant-Versorgung mit modernen Implantaten erlaubt eine weitere Verbesserung des Sprachverst?ndnisses und die Wiederherstellung des r?umlichen H?rens. Entsprechend hat sich das Indikationsspektrum mehr und mehr in Richtung Resth?rigkeit verschoben. Technische Weiterentwicklungen betrafen die implantierbare Elektronik, die Elektroden selbst oder die verwendeten Sprachkodierungsstrategien. Aus der Vielzahl der modifizierbaren Parameter ergibt sich oft eine komplexe Wechselwirkung. Weiterentwicklungen vom erreichten, hohen Standard aus unterliegen grunds?tzlich natürlich auch dem Risiko, die gewünschten Ziele nicht im erhofften Umfang zu erreichen. Anl?sslich der Sitzungen “Cochlear Implants” im Rahmen des Deutsch-?sterreichischen HNO-Kongresses 2002 in Baden-Baden soll ein kurzer überblick zum Stand der Thematik gegeben und gegenw?rtige Entwicklungen bzw. Entwicklungsm?glichkeiten kritisch beleuchtet werden.     

Cochlear implant candidate selection

In recent years there has been an increased acceptance of the cochlear implant as an appropriate sensory aid for selected hearing-impaired individuals with profound losses. With the Food and Drug Administration's release of the 3M/House single channel cochlear implant on November 29, 1984 and the Nucleus 22-channel cochlear implant on October 31, 1985 it is anticipated that many new groups of otologists and audiologists will have direct involvement in this exciting new approach to the management of patients with profound hearing impairments. This report reviews our cochlear implant selection protocol for the severe to profound adult hearing-impaired population.     

Case report: Cochlear implant magnet migration

A 13-month-old cochlear implant recipient underwent routine device activation. Three months postoperatively, the patient sustained a fall with contact to the area of the implant without immediate complication. Ten months postoperatively, the position of the external coil appeared to have moved and the patient did not seem to be responding as well to sound. Audiological testing could not elicit normal device impedances. AP and lateral plain radiographs of the skull revealed migration of the internal magnet from its position within the internal coil to a position over the receiver/stimulator. This is the first known published case of cochlear implant magnet migration.     

Cochlear implant electronics made simple

Electronics used in cochlear implants are relatively straightforward. While all cochlear implants process signals by amplifying, compressing, filtering, and encoding them for transmission to and use by the receiver, there are significant electronic variations amongst cochlear implant systems. The evolving nature of cochlear implant research and development makes it difficult, at the least, to predict the optimum electronic configuration. Since the biologic system which this prosthesis replaces is subject to so many forms and degrees of pathology, there is likely no one best answer. Since their first use in 1957, cochlear implants have steadily evolved to their current state. Much is still unknown about the biologic system on which they operate. It is exciting to contemplate that this biologic system, even though damaged, may be made more understandable by the same device which restores some hearing function.     

Pediatric Cochlear implant soft failure

Purpose

Hard cochlear implant failures are diagnosed by objective tests whereas soft failures are suspected on the basis of clinical signs and symptoms. This study reviews our experience with children in tertiary pediatric medical center who underwent revision cochlear implantation, with emphasis on soft failures.

The development of the Nucleus Freedom Cochlear implant system

Cochlear Limited (Cochlear) released the fourth-generation cochlear implant system, Nucleus Freedom, in 2005. Freedom is based on 25 years of experience in cochlear implant research and development and incorporates advances in medicine, implantable materials, electronic technology, and sound coding. This article presents the development of Cochlear's implant systems, with an overview of the first 3 generations, and details of the Freedom system: the CI24RE receiver-stimulator, the Contour Advance electrode, the modular Freedom processor, the available speech coding strategies, the input processing options of Smart Sound to improve the signal before coding as electrical signals, and the programming software. Preliminary results from multicenter studies with the Freedom system are reported, demonstrating better levels of performance compared with the previous systems. The final section presents the most recent implant reliability data, with the early findings at 18 months showing improved reliability of the Freedom implant compared with the earlier Nucleus 3 System. Also reported are some of the findings of Cochlear's collaborative research programs to improve recipient outcomes. Included are studies showing the benefits from bilateral implants, electroacoustic stimulation using an ipsilateral and/or contralateral hearing aid, advanced speech coding, and streamlined speech processor programming.     

Cochlear implant infection due to cholesteatoma

Abstract

There are an increasing number of young children undergoing cochlear implantation. Cholesteatoma is a serious, although rare, long-term complication. We present the only documented case in which cholesteatoma has presented with late abscess formation in the bed of a cochlear implant package of a child. Cholesteatoma may be an iatrogenic complication of implantation surgery. Damage to the bony part of the external auditory canal should be avoided. The successful two-staged surgical treatment using explantation, debridement, gentamycin bead insertion, cholesteatoma excision and modified radical mastoidectomy is described. The intra-cochlear electrode was removed precluding cochlear implant reimplantation. This late presentation supports regular longterm otoscopic review of cochlear implant patients by experienced otologists. Suspicion should be raised in patients with persistent otorrhoea. Copyright © 2005 John Wiley & Sons, Ltd.     

Cochlear implant failures and revision.

OBJECTIVE: To review cases involving implant failure and revision surgery in a large cochlear implant program. STUDY DESIGN: Retrospective case series. SETTING: Cochlear implant program in an academic medical center. PATIENTS: Adults and children who underwent revision cochlear implantation (n = 58). INTERVENTION: Diagnosis and explantation of failed cochlear implants, with subsequent reimplantation. Assessment of implant function and speech perception. MAIN OUTCOME MEASURES: Device type, time from implantation to revision, cause of failure, performance with original implant versus revision, number of electrodes placed, and surgical challenges related to reimplantation. RESULTS: Forty-five patients initially implanted at this program and 13 patients implanted elsewhere underwent revision surgery. The institutional device failure rate was 3.7% and the overall revision rate was 5.1%. Reasons for implant revision included documented internal device failure (46%), scalp flap complications (17%), optimization of electrode placement (13%), unexplained deterioration of performance (12%), technology upgrade (10%), and intratemporal pathology (3%). Revision surgery typically involved only minor anatomic challenges, but five patients required circumodiolar drillout procedures to improve electrode position. Electrode insertion was equal or deeper in 53 of 58 cases. Speech perception ability decreased in only three patients. CONCLUSIONS: Management of implant failures and performance of revision surgery are becoming increasingly important in cochlear implant programs. Outcomes are generally excellent. Revision implantation is a safe and appropriate procedure that should be pursued in a timely fashion when patients experience cochlear implant failure.