Bone-anchored devices in single-sided deafness

Single sided deafness (SSD) implies sensorineural hearing loss in one ear with normal contralateral hearing function. Traditionally, SSD patients have been overlooked due to a belief that the preserved functioning of the contralateral ear compensates for the nonhearing side. SSD patients however experience multiple audiological difficulties, particularly when the sound source is situated on the non-hearing side or in the presence of competing sounds. Through reviewing current literature, we describe the role of bone-anchored devices (Baha) in the management of SSD patients. Recent publications for Baha in SSD have demonstrated consistent objective and subjective improvement in audiologic metrics when compared to unaided conditions. There is also evidence of benefit provided by Baha by the Abbreviated Profile of Hearing Aid Benefit, in global measures of ease of communication, reverberation, and background noise, but not typically in aversiveness to sounds. Interestingly, despite some patients gaining minimal objective or subjective benefits, the majority of these patients still report improved quality of life and would recommend the procedure. Despite increasing evidence for the role of Baha in the management of SSD in the literature, much of these data are based on older technology. Further reports should specify the processor type used and the etiology of the hearing loss to ensure accuracy of future data.

Restoration of Auditory Nerve Synapses in Cats by Cochlear Implants

Congenital deafness results in abnormal synaptic structure in endings of the auditory nerve. If these abnormalities persist after restoration of auditory nerve activity by a cochlear implant, the processing of time-varying signals such as speech would likely be impaired. We stimulated congenitally deaf cats for 3 months with a six-channel cochlear implant. The device used human speech-processing programs, and cats responded to environmental sounds. Auditory nerve fibers exhibited a recovery of normal synaptic structure in these cats. This rescue of synapses is attributed to a return of spike activity in the auditory nerve and may help explain cochlear implant benefits in childhood deafness.

Benign positional vertigo after cochlear implantation

OBJECTIVE

To identify patients who underwent cochlear implantation (CI) and who subsequently developed benign positional vertigo (BPV) after the procedure and to identify any contributing factors.

STUDY DESIGN AND SETTING

Academic tertiary referral center. Cochlear implant recipients' medical records were retrospectively reviewed to identify patients with both vertigo and, more specifically, BPV. Preoperative, intraoperative, and postoperative factors were studied vis-a-vis the development of BPV.

RESULTS

BPV was newly diagnosed in 12 patients after CI. The etiology of hearing loss included presbycusis (16.6%), autoimmune inner ear disease (16.6%), congenital hearing loss (41.6%), Meniere's disease (8.3%), prematurity (8.3%), and idiopathic factors (8.3%). The onset of BPV varied after the procedure (mean +/- SD, 292 +/- 309 days). BPV symptoms did not affect implant performance. All patients were treated for BPV by Epley's maneuver and vestibular exercises. Symptoms disappeared in 11 patients and persisted in 1.

CONCLUSIONS

BPV is an uncommon development after CI, although it occurs more frequently than in the general population. Two theories are proposed: the introduction of bone dust into the labyrinth and the dislodging of otoconia during surgery. The diagnosis, treatment, and prognosis of BPV after CI do not differ from those for non-CI-associated BPV.

SIGNIFICANCE

Dizziness after CI usually develops as a result of vestibular hypofunction. BPV, which is a hyperfunctioning form of vestibular dysfunction, should be recognized as a possible sequelae of CI.

Safety and patient experience with transtympanic electrocochleography

OBJECTIVES/HYPOTHESIS

Transtympanic electrocochleography (t-ECOG) is a sensitive diagnostic instrument used for Meniere's disease. It is sensitive by virtue of the recording electrode's position on the promontory of the cochlea where the signals are generated. There is concern about the invasive nature of t-ECOG in comparison to extratympanic recording techniques. The purpose of this study was to examine the safety issues, complications, and patient experience with t-ECOG.

STUDY DESIGN

Observational study utilizing retrospective chart review and patient survey.

METHODS

The medical records of 205 patients who underwent t-ECOG were reviewed for complications. Complications included persistent tympanic membrane perforation, hearing loss, otitis media, otitis externa, ear canal injury, hemotympanum, and pain. An additional 36 patients undergoing t-ECOG were surveyed on subjective measures such as pain during topical anesthesia of the tympanic membrane, during transtympanic placement of the needle electrode, and during the test procedure and overall experience with t-ECOG.

RESULTS

There was one case of a nonhealed, persistent perforation in the setting of acute otitis media directly as a result of t-ECOG. Two patients developed otitis media, and three patients had ear pain for up to 5 days. All 36 patients felt the procedure to be tolerable with minimal discomfort.

CONCLUSIONS

Transtympanic electrocochleography may be performed with good patient acceptance and infrequent complications.

Hearing Rehabilitation Using the BAHA Bone-Anchored Hearing Aid: Results in 40 Patients

OBJECTIVE

This study evaluates the U.S. experience with the first 40 patients who have undergone audiologic rehabilitation using the BAHA bone-anchored hearing aid.

STUDY DESIGN

This study is a multicenter, nonblinded, retrospective case series.

SETTING

Twelve tertiary referral medical centers in the United States.

PATIENTS

Eligibility for BAHA implantation included patients with a hearing loss and an inability to tolerate a conventional hearing aid, with bone-conduction pure tone average levels at 60 dB or less at 0.5, 1, 2, and 4 kHz.

INTERVENTION

Patients who met audiologic and clinical criteria were implanted with the Bone-Anchored Hearing Aid (BAHA, Entific Corp., Gothenburg, Sweden).

MAIN OUTCOME MEASURES

Preoperative air- and bone-conduction thresholds and air-bone gap; postoperative BAHA-aided thresholds; hearing improvement as a result of implantation; implantation complications; and patient satisfaction.

RESULTS

The most common indications for implantation included chronic otitis media or draining ears (18 patients) and external auditory canal stenosis or aural atresia (7 patients). Overall, each patient had an average improvement of 32+/-19 dB with the use of the BAHA. Closure of the air-bone gap to within 10 dB of the preoperative bone-conduction thresholds (postoperative BAHA-aided threshold vs. preoperative bone-conduction threshold) occurred in 32 patients (80%), whereas closure to within 5 dB occurred in 24 patients (60%). Twelve patients (30%) demonstrated 'overclosure' of the preoperative bone-conduction threshold of the better hearing ear. Complications were limited to local infection and inflammation at the implant site in three patients, and failure to osseointegrate in one patient. Patient response to the implant was uniformly satisfactory. Only one patient reported dissatisfaction with the device.

CONCLUSIONS

The BAHA bone-anchored hearing aid provides a reliable and predictable adjunct for auditory rehabilitation in appropriately selected patients, offering a means of dramatically improving hearing thresholds in patients with conductive or mixed hearing loss who are otherwise unable to benefit from traditional hearing aids.

The societal costs of severe to profound hearing loss in the United States

OBJECTIVE

Severe to profound hearing impairment affects one-half to three-quarters of a million Americans. To function in a hearing society, hearing-impaired persons require specialized educational, social services, and other resources. The primary purpose of this study is to provide a comprehensive, national, and recent estimate of the economic burden of hearing impairment.

METHODS

We constructed a cohort-survival model to estimate the lifetime costs of hearing impairment. Data for the model were derived principally from the analyses of secondary data sources, including the National Health Interview Survey Hearing Loss and Disability Supplements (1990-91 and 1994-95), the Department of Education's National Longitudinal Transition Study (1987), and Gallaudet University's Annual Survey of Deaf and Hard of Hearing Youth (1997-98). These analyses were supplemented by a review of the literature and consultation with a four-member expert panel. Monte Carlo analysis was used for sensitivity testing.

RESULTS

Severe to profound hearing loss is expected to cost society $297,000 over the lifetime of an individual. Most of these losses (67%) are due to reduced work productivity, although the use of special education resources among children contributes an additional 21%. Lifetime costs for those with prelingual onset exceed $1 million.

CONCLUSIONS

Results indicate that an additional $4.6 billion will be spent over the lifetime of persons who acquired their impairment in 1998. The particularly high costs associated with prelingual onset of severe to profound hearing impairment suggest interventions aimed at children, such as early identification and/or aggressive medical intervention, may have a substantial payback.

Cost-utility analysis of the cochlear implant in children

CONTEXT

Barriers to the use of cochlear implants in children with profound deafness include device costs, difficulty assessing benefit, and lack of data to compare the implant with other medical interventions.

OBJECTIVE

To determine the quality of life and cost consequences for deaf children who receive a cochlear implant.

DESIGN

Cost-utility analysis using preintervention, postintervention, and cross-sectional surveys conducted from July 1998 to May 2000.

SETTING

Hearing clinic at a US academic medical center.

PARTICIPANTS

Parents of 78 profoundly deaf children (average age, 7.5 years) who received cochlear implants.

MAIN OUTCOME MEASURES

Direct and total cost to society per quality-adjusted life-year (QALY) using the time-trade-off (TTO), visual analog scale (VAS), and Health Utilities Index-Mark III (HUI), discounting costs and benefits 3% annually. Parents rated their child's health state at the time of the survey and immediately before and 1 year before implantation.

RESULTS

Recipients had an average of 1.9 years of implant use. Mean VAS scores increased by 0. 27, from 0.59 before implantation to 0.86 at survey. In a subset of participants, TTO scores increased by 0.22, from 0.75 to 0.97 (n = 40) and HUI scores increased by 0.39, from 0.25 to 0.64 (n = 22). Quality-of-life scores were no different 1 year before and immediately before implantation. Discounted direct costs were $60,228, yielding $9,029 per QALY using the TTO, $7,500 per QALY using the VAS, and $5,197 per QALY using the HUI. Including indirect costs such as reduced educational expenses, the cochlear implant provided a savings of $53,198 per child.

CONCLUSIONS

Cochlear implants in profoundly deaf children have a positive effect on quality of life at reasonable direct costs and appear to result in a net savings to society. JAMA. 2000;284:850-856

Intracanalicular schwannoma of the facial nerve: a manifestation of neurofibromatosis type 2

Primary facial nerve tumors, which are relatively uncommon, can present a diagnostic dilemma based on their location and variable pattern of symptoms. Of primary cranial nerve tumors, schwannomas of the facial nerve rank third in frequency after those of the eighth and fifth cranial nerves. We report an illustrative case of an intracanalicular schwannoma associated with several central nervous system tumors, consistent with neurofibromatosis type 2. Initially assumed to be an eighth cranial nerve tumor, the schwannoma was found intraoperatively to arise from the facial nerve. Early diagnosis and treatment enabled excision of the tumor without sacrifice of the facial nerve. Facial nerve schwannomas can resemble acoustic schwannomas in their clinical presentation. Only a heightened level of clinical vigilance will point to the correct diagnosis and result in an optimal therapeutic outcome for patients with these rare tumors.

Activity influences on neuronal connectivity within the auditory pathway

HYPOTHESIS

Sensorineural hearing loss may be associated with altered patterns of neuronal connections within the central auditory pathway.

STUDY DESIGN

The cat auditory system was used to address the relative importance of impulse traffic within the auditory nerve in maintaining central nervous system connections.

METHODS

Acute, unilateral deafness was induced by tetrodotoxin intoxication of cochlear hair cells. Analysis focused on the structural patterns of contact between auditory nerve endings called end bulbs of Held and their target neurons. Specifically, end bulb morphology and target cell size within the cochlear nucleus were examined. Highly specialized synaptic contacts at this junction provide a powerful site for study.

RESULTS

The principal finding was that abolished activity in the auditory nerve caused nerve endings to assume a different shape, typified by more branching and smaller terminal swellings. The new shape is one typically associated with only a subpopulation of fibers in normal-hearing cats--those exhibiting a high-threshold, low-spontaneous activity profile. This result implies that abolished activity alters patterns of nerve fiber contact with second-order neurons. Tetrodotoxin produced differential effects on subpopulations of target neurons within the brainstem and is interpretable on the basis of "weighing" synaptic inputs. Second-order neurons that receive large axosomatic inputs from their parent fiber were significantly smaller than neurons that receive small, axodendritic terminals. Thus, attenuated auditory activity may produce differential effects across the auditory pathway, thereby disrupting the normal balance of inputs into synaptic stations.

CONCLUSIONS

Impulse traffic is a critical factor in the interaction between the ear and central auditory stations and appears necessary for the maintenance of key synapses. As hearing disorders with impaired comprehension may be modeled by studies of auditory deafferentation, these observations extend the possibility that changes in central neuronal connections underlie reduced capabilities for processing restored auditory input.

Cost-utility of the cochlear implant in adults: a meta-analysis

OBJECTIVE

To conduct a meta-analysis of the cost-utility of the cochlear implant in adults.

DATA SOURCES

MEDLINE literature search, review of article bibliographies, and consultation with experts.

STUDY SELECTION

Studies that reported (1) data on adults (age > or = 18 years) with bilateral, postlingual, profound deafness; (2) a health-utility gain from cochlear implantation on a scale from 0.00 (death) to 1.00 (perfect health); (3) a cost-utility ratio in terms of dollars per quality-adjusted life-year (QALY); and (4) at least 1 conventional statistical parameter (ie, SD, 95% confidence interval [CI], or P value).

DATA EXTRACTION

From each study, we extracted the number of subjects, study design, health-utility instrument used, health-utility associated with profound deafness, health-utility gain from cochlear implantation, cost-utility of cochlear implantation, and reported statistical parameters.

DATA SYNTHESIS

Weighted averages were calculated using a statistical weight of 1 per variance. Pooling 9 reports (n = 619), the health-utility of profoundly deaf adults without cochlear implants was 0.54 (95% CI, 0.52-0.56). Pooling 7 studies (n = 511), the health-utility of profoundly deaf adults after cochlear implantation was 0.80 (95% CI, 0.78-0.82). This improvement of 0.26 in health-utility resulted in a cost-utility ratio of $12,787 per QALY.

CONCLUSIONS

Profound deafness in adults results in a substantial health-utility loss. Over half of that loss is restored after cochlear implantation, yielding a cost-utility ratio of $12,787 per QALY. This figure compares favorably with medical and surgical interventions that are commonly covered by third-party payers in the United States today.

A prospective study of the cost-utility of the multichannel cochlear implant

CONTEXT

Prior clinical studies have indicated that cochlear implantation provides benefits to individuals with advanced sensorineural hearing loss who are unable to gain effective speech recognition with hearing aids.

OBJECTIVE

To determine the cost per quality-adjusted life-year (QALY) for adults receiving multichannel cochlear implants.

DESIGN

Prospective 12-month multicenter study using preference-based quality-of-life measures and total cost determinations, comparing profoundly hearing-impaired adult subjects with and without cochlear implants.

SETTING

Hospital-based and patient-resource clinics.

PATIENTS

Severely to profoundly hearing-impaired adult recipients of a cochlear implant and adults eligible for the device who had not yet received it.

MAIN OUTCOME MEASURE

Clinical assessment of implant participants included medical and audiologic (speech understanding) data at the time of enrollment, 6 months, and 12 months. All participants' health-utility was assessed at the time of enrollment, 6 months, and 12 months using the Health Utility Index. One-year medical resource utilization and cost data included bills related to implants, patient diaries, charge estimates from clinical sites, and published literature. A decision model was developed to determine cost per QALY.

RESULTS

Of the 84 enrolled adults, 62 (75%) completed the study. Mean health-utility scores at the time of enrollment were identical between groups. The marginal 12-month health-utility gain for implant recipients was 0.20; 90% of this improvement was achieved within 6 months. For patients with a mean 22-year life expectancy, the marginal cost per QALY was $14,670.

CONCLUSIONS

Overall, multichannel cochlear implants significantly improved recipients' performance on measures of speech understanding and ratings of health-utility within 6 months of implantation. The multichannel cochlear implant yielded a very favorable cost per QALY.

Trends in educational placement and cost-benefit considerations in children with cochlear implants

OBJECTIVES

To study the effect of cochlear implantation on the use of educational resources by profoundly hearing-impaired children and to determine trends in educational cost vs benefit.

DESIGN

Retrospective study and cost-benefit analysis.

SETTING

Outpatient pediatric cochlear implant program in an academic institution (The Listening Center at Johns Hopkins University School of Medicine, Baltimore, Md), in collaboration with public schools in Maryland and surrounding states.

PATIENTS OR OTHER PARTICIPANTS

School-aged children with profound prelingual hearing impairment without other clearly defined disabilities. Thirty-five children with multiple-channel cochlear prostheses and a comparison group of 10 children without implants from 'total communication' programs in the Maryland public school system.

INTERVENTIONS

Multiple-channel cochlear implantation and at least 1 year of a systematic auditory skill development program at the Listening Center, compared with standard educational management of children with conventional amplification.

MAIN OUTCOME MEASURES

Classroom placement and number of hours of special educational support used.

RESULTS

A correlation was observed between the length of cochlear implant experience and the rate of full-time placement in mainstream classrooms (r = 0.10; P= .04). There was also a negative correlation between the length of implant experience and the number of hours of special educational support used by fully mainstreamed children (Pearson product moment correlation = -0.10; P = .03). Children with greater than 2 years of implant experience were mainstreamed at twice the rate or more of age-matched children with profound hearing loss who did not have implants. They were also placed less frequently in self-contained classrooms and used fewer hours of special education support. A cost-benefit analysis based on conservative estimates of educational expenses from kindergarten to 12th grade shows a cost savings of cochlear implantation and appropriate auditory (re)habilitation that ranges from $30000 to $200000.

CONCLUSIONS

Cochlear implantation accompanied by aural (re)habilitation increases access to acoustic information of spoken language, leading to higher rates of mainstream placement in schools and lower dependence on special education support services. The cost savings that results from a decrease in the use of support services indicates an educational cost benefit of cochlear implant (re)habilitation for many children.

Meta-analysis of pediatric cochlear implant literature

We analyzed published reports of the effect of age at implantation and the cause of and age at onset of deafness on speech perception benefit in children with cochlear implants, and compared these results with those of unreported trials of multichannel cochlear implants. Combining data from published and unpublished patient series was constrained by differences in test protocols between studies, but was made feasible by employing a meta-analysis in which data were converted into an ordinal classification scale that represented levels of communicative benefit. Results showed that more rapid gains in speech perception are associated with earlier age at implantation, and that speech perception results are independent of cause of or age at onset of deafness after 1 year of implant use. Moreover, with minor exceptions, there was no statistical difference between published and unpublished data, thereby indicating no publication bias in the literature. A meta-analytic approach is useful because it can clarify the quality of reported data and the direction of future research and, hopefully, foster collaboration in conducting and reporting future research. A standardized approach to reporting results in children is advised in order to produce a balanced interpretation of implant benefit and to facilitate wider understanding and dissemination of study conclusions.

Single unit recordings in the auditory nerve of congenitally deaf white cats: morphological correlates in the cochlea and cochlear nucleus

It is well known that experimentally induced cochlear damage produces structural, physiological, and biochemical alterations in neurons of the cochlear nucleus. In contrast, much less is known with respect to the naturally occurring cochlear pathology presented by congenital deafness. The present study attempts to relate organ of Corti structure and auditory nerve activity to the morphology of primary synaptic endings in the cochlear nucleus of congenitally deaf white cats. Our observations reveal that the amount of sound-evoked spike activity in auditory nerve fibers influences terminal morphology and synaptic structure in the anteroventral cochlear nucleus. Some white cats had no hearing. They exhibited severely reduced spontaneous activity and no sound-evoked activity in auditory nerve fibers. They had no recognizable organ of Corti, presented >90% loss of spiral ganglion cells, and displayed marked structural abnormalities of endbulbs of Held and their synapses. Other white cats had partial hearing and possessed auditory nerve fibers with a wide range of spontaneous activity but elevated sound-evoked thresholds (60-70 dB SPL). They also exhibited obvious abnormalities in the tectorial membrane, supporting cells, and Reissner's membrane throughout the cochlear duct and had complete inner and outer hair cell loss in the base. The spatial distribution of spiral ganglion cell loss correlated with the pattern of hair cell loss. Primary neurons of hearing-impaired cats displayed structural abnormalities of their endbulbs and synapses in the cochlear nucleus which were intermediate in form compared to normal and totally deaf cats. Changes in endbulb structure appear to correspond to relative levels of deafness. These data suggest that endbulb structure is significantly influenced by sound-evoked auditory nerve activity.

A model of educational resource use by children with cochlear implants

We have tracked patterns of use of educational and rehabilitative resources as part of an initial assessment of cost-benefit ratios of cochlear implants in children. Forty-two children with cochlear implants in the Listening Center at Johns Hopkins program of aural rehabilitation have served as our study cohort to develop the measures to be assessed. An educational resource matrix stratifies school setting (residential vs special education vs non-specialized "mainstream" setting) and levels of rehabilitative support (speech and language therapy and interpreter use) to map past and current use of these services. Initial cost-benefit projections based on observed advancement toward educational independence in the educational resource matrix indicate an extremely favorable net present value of the implant (cost savings minus cost). These cost-benefit projections will need to be supplemented with measures of the impact on quality of life and future educational and vocational options to determine the overall cost-effectiveness of cochlear implants in children.

Cochlear nucleus cell size changes in the dalmatian: model of congenital deafness

We assessed cellular changes in one population of neurons of the cochlear nucleus associated with a form of genetic deafness in deaf dalmatians. Spheric cells from deaf dalmatians and age-matched control (hearing) dogs were analyzed morphometrically. The somatic silhouette of these cells was reduced by 22.1% to 38.1%. The effect on cell size was greater with increased duration of deafness. Because the deaf dalmatian exhibits progressive degeneration of the auditory periphery, shrinkage of spheric cells may reflect the initial influence of attenuated activity of auditory nerve fibers, and sensorineural degeneration with longer periods of deafness.

Ultrastructural analysis of primary endings in deaf white cats: morphologic alterations in endbulbs of Held

Changes in structure and function of the auditory system can be produced by experimentally manipulating the sensory environment, and especially dramatic effects result from deprivation procedures. An alternative deprivation strategy utilizes naturally occurring lesions. The congenitally deaf white cat represents an animal model of sensory deprivation because it mimics a form of human deafness called the Scheibe deformity and permits studies of how central neurons react to early-onset cochlear degeneration. We studied the synaptic characteristics of the endbulb of Held, a prominent auditory nerve terminal in the cochlear nucleus. Endbulbs arise from the ascending branch of the auditory nerve fiber and contact the cell body of spherical bushy cells. After 6 months, endbulbs of deaf white cats exhibit alterations in structure that are clearly distinguishable from those of normal hearing cats, including a diminution in terminal branching, a reduction in synaptic vesicle density, structural abnormalities in mitochondria, thickening of the pre- and postsynaptic densities, and enlargement of synapse size. The hypertrophied membrane densities are suggestive of a compensatory response to diminished transmitter release. These data reveal that early-onset, long-term deafness produces unambiguous alterations in synaptic structure and may be relevant to rehabilitation strategies that promote aural/oral communication.

Implantation of the lateral cochlear wall for auditory nerve stimulation

Although cochlear implants now regularly achieve gratifying results, traditional intrascalar implants have certain limitations. Extraluminal implants may offset some of these problems by accessing neurons subserving a wider tonotopic range, avoiding intracochlear insertion trauma, and offering alternatives when cochlear obliteration is present. We have investigated the utility of a lateral cochlear wall implant in a normal-hearing cat model with implants at the middle and basal turns, and found successful activation of the auditory nerve at thresholds of 28.1 and 40.6 microA, respectively. No adventitial stimulation of the facial nerve was noted within the dynamic range. Maximum responsiveness was observed with implants of the middle turn of the cochlea, an area that is not reliably approached with current intrascalar implants. These observations support and extend prior observations of the feasibility of extraluminal stimulation of the auditory nerve.

Facial nerve injury in acoustic neuroma (vestibular schwannoma) surgery: etiology and prevention

Facial nerve injury associated with acoustic neuroma surgery has declined in incidence but remains a clinical concern. A retrospective analysis of 611 patients surgically treated for acoustic neuroma between 1973 and 1994 was undertaken to understand patterns of facial nerve injury more clearly and to identify factors that influence facial nerve outcome. Anatomical preservation of the facial nerve was achieved in 596 patients (97.5%). In the immediate postoperative period, 62.1% of patients displayed normal or near-normal facial nerve function (House-Brackmann Grade 1 or 2). This number rose to 85.3% of patients at 6 months after surgery and by 1 year, 89.7% of patients who had undergone acoustic neuroma surgery demonstrated normal or near-normal facial nerve function. The surgical approach appeared to have no effect on the incidence of facial nerve injury. Poor facial nerve outcome (House-Brackmann Grade 5 or 6) was seen in 1.58% of patients treated via the suboccipital approach and in 2.6% of patients treated via the translabyrinthine approach. When facial nerve outcome was examined with respect to tumor size, there clearly was an increased incidence of facial nerve palsy seen in the immediate postoperative period in cases of larger tumors: 60.8% of patients with tumors smaller than 2.5 cm had normal facial nerve function, whereas only 37.5% of patients with tumors larger than 4 cm had normal function. This difference was less pronounced, however, 6 months after surgery, when 92.1% of patients with tumors smaller than 2.5 cm had normal or near normal facial function, versus 75% of patients with tumors larger than 4 cm. The etiology of facial nerve injury is discussed with emphasis on the pathophysiology of facial nerve palsy. In addition, on the basis of the authors' experience with these complex tumors, techniques of preventing facial nerve injury are discussed.

Effect of adult-onset deafness on the human central auditory system

Degenerative change in the central auditory system was assessed in seven subjects with profound bilateral adult-onset deafness. The degree of transneuronal atrophy was determined by measuring cell size at three levels of the brain stem auditory pathway (anteroventral cochlear nucleus, medial superior olivary nucleus, and inferior colliculus). Within subjects, the relative degree of cell shrinkage was similar across all levels of the central pathway. Across subjects, the best neuronal preservation was seen in a case of viral labyrinthitis with 1 year of bilateral dearness and a near-normal population of cochlear ganglion cells. Reduction in cell size was greatest in cases of bacterial labyrinthitis or Scheibe degeneration with reduced populations of ganglion cells and longer periods of deafness. At the level of the cochlear nucleus, there was no consistent difference in cell size between the side stimulated by a functioning prosthetic device and the nonstimulated side.

Ultrastructural changes in primary endings of deaf white cats

Changes in brain structure occur as a consequence of altered experience. During maturation of the auditory nervous system, sensory deprivation is known to cause cell loss, abnormal axonal projections, and synaptic alterations. These animal data may be relevant to clinical observations that cochlear implants provide superior benefit for individuals who become deaf postlingually compared with those who become deaf prelingually. That is, implantation appears most efficacious if it occurs after functional connections are established but before deprivation-induced changes in the central auditory system. After this period, synaptic reorganization may underlie the diminished effectiveness of cochlear implants.

Morphological changes in the cochlear nucleus of congenitally deaf white cats

Investigations in animal models and humans have indicated that congenital deafness produces degenerative changes in the central auditory pathway. The cochlear nucleus is the first central structure that receives cochlear input, and may be considered the origin of ascending auditory pathways. In this context, we studied congenitally deaf white cats, who express early onset cochlear receptor loss, in order to assess the nature of structural changes in cells of the cochlear nucleus. It is conceivable that pathologic alterations in higher auditory structures are transneuronally distributed through this nucleus. The cochlear nuclei of nonwhite cats with normal hearing were compared to those of deaf white cats exhibiting hearing loss in excess of 70 dB SPL. The cochlear nuclei of the deaf white cats were smaller in volume by roughly 50%, with the ventral and dorsal divisions being equally affected. Cell body silhouette area was determined for spherical bushy cells of the anteroventral cochlear nucleus (AVCN), pyramidal cells of the dorsal cochlear nucleus (DCN), sensory neurons from the principal trigeminal nucleus, and motoneurons of the facial nucleus. We found no statistical difference in neuronal cell body size between nonauditory neurons of these two groups of cats, whereas auditory neurons of deaf white cats were 30.8-39.4% smaller than those of normal cats. These data imply that neuronal changes in congenitally deaf cats are specific to the auditory pathway. Although cochlear nucleus volume loss was uniform for both divisions, there was a differential effect on cell density: AVCN cell density increased by 40%, whereas DCN cell density was relatively unaffected (10% increase). Astrocyte density was also greater in the AVCN (52%) compared to that in the DCN (5%). These observations reveal a differential impact on cells in the cochlear nucleus to congenital deafness, suggesting selective processing impairment at this level. If similar patterns of degeneration occur in humans, such pathologies may underlie reduced processing of input from cochlear implants in congenitally deaf adults.

Trauma to the external auditory canal and temporal bone

Sources of trauma to the external auditory canal range from impaction of small foreign bodies to severely comminuted temporal bone fractures sustained after blunt or penetrating forces. This article provides an overview of commonly encountered injuries. The proposed systematic approach to evaluation and management is meant to serve as a guide to individualizing patient care.

Cost utility of the multichannel cochlear implants in 258 profoundly deaf individuals

Cost utility analysis is a method of cost-effectiveness analysis which provides results in terms of cost per quality-adjusted life-year (QALY). Cost utility for the multichannel cochlear implant was calculated using Ontario Health Utilities Index data from 229 Nucleus 22-channel implant users and 32 cochlear implant candidates awaiting surgery. The health utility of the implanted group was greater than that of the candidate group by 0.204 (P<.0001). Use of this figure in a cost utility calculation indicates that cochlear implantation costs approximately $15,928 per QALY provided. Sensitivity analysis, a technique which systematically varies the assumptions underlying the calculations, suggests a range for the true value of between $12,000 and $30,000. This compares very favorably with other medical interventions. It is concluded that profound hearing loss has a significant effect on quality of life, and measurement of the changes that result from cochlear implant use indicates that this technology provides significant improvements and is quite cost-effective.

Titanium-anchored prostheses in otology

In the late 1970s, Per-Ingvar Branemark and coworkers in Goteberg, Sweden, successfully introduced osseointegrated titanium implants into clinical practice. They had achieved the previously elusive goal of producing stable, secure percutaneous implants anchored in underlying cortical bone. Two applications of these implants to otology were obvious: (1) to provide a coupling for bone-conduction hearing aids and (2) to provide fixation points for anchoring of auricular prostheses. Before describing the current state of these clinical applications and considering future potential uses, the authors review the basis for titanium osseointegration.