Evaluation of four Cochlear Implant Designs

Multichannel cochlear implant systems that provide spectral information in addition to temporal and intensity cues are consistently allowing profoundly deafened postlingual adults to recognize some words without visual cues. All four of the devices enhance speech-reading ability and provide useful information about nonspeech sounds. The multichannel implant patients are generally functioning at a higher level in this limited random series.

Vowel and Consonant Confusions among Cochlear Implant Patients: Do Different Implants Make a Difference?

Vowel and consonant confusions were obtained from two patients, one using the Melbourne implant (M3) and one the Utah device (U1). The confusion matrices were analyzed using information transfer analysis and multidimensional scaling. The results from the two patients were generally consistent with the different processing strategies of their implants. For the vowels, M3 appeared to be processing second formant (F2) and duration, whereas U1 appeared to be attending primarily to first formant (F1) and duration. For the consonants, the responses of M3 reflected sensitivity to frication, voicing, and envelope, whereas the results from U1 suggested sensitivity to voicing, nasal, frication, and possibly “place” information.

Plasticity in human pitch perception induced by tonotopically mismatched electro-acoustic stimulation

Under normal conditions, the acoustic pitch percept of a pure tone is determined mainly by the tonotopic place of the stimulation along the cochlea. Unlike acoustic stimulation, electric stimulation of a cochlear implant (CI) allows for the direct manipulation of the place of stimulation in human subjects. CI sound processors analyze the range of frequencies needed for speech perception and allocate portions of this range to the small number of electrodes distributed in the cochlea. Because the allocation is assigned independently of the original resonant frequency of the basilar membrane associated with the location of each electrode, CI users who have access to residual hearing in either or both ears often have tonotopic mismatches between the acoustic and electric stimulation. Here we demonstrate plasticity of place pitch representations of up to three octaves in Hybrid CI users after experience with combined electro-acoustic stimulation. The pitch percept evoked by single CI electrodes, measured relative to acoustic tones presented to the non-implanted ear, changed over time in directions that reduced the electro-acoustic pitch mismatch introduced by the CI programming. This trend was particularly apparent when the allocations of stimulus frequencies to electrodes were changed over time, with pitch changes even reversing direction in some subjects. These findings show that pitch plasticity can occur more rapidly and on a greater scale in the mature auditory system than previously thought possible. Overall, the results suggest that the adult auditory system can impose perceptual order on disordered arrays of inputs.

Histopathology of the Clarion cochlear implant electrode positioner in a human subject

A Silastic electrode positioner was introduced by the Advanced Bionics Corporation in 1999 and it was designed to achieve a perimodiolar position of the stimulating electrode. The positioner was voluntarily recalled in the United States in July 2002 due to an apparent higher risk of bacterial meningitis in patients in whom the electrode positioner had been placed. A detailed histopathologic study of the positioner in the human has not previously been published. The histopathologic findings in a 74-year-old woman who underwent bilateral cochlear implantation using the positioner are presented. Findings include a large track caused by the combined electrode and its positioner with considerable disruption of the basilar membrane and osseous spiral lamina. Although there was a fibrous sheath around the electrode and positioner at the cochleostomy in both ears, this fibrous sheath did not extend deeply into the cochlea except at the apical end of the electrode beyond the positioner. This resulted in a large fluid space around and between the positioner and electrode within the cochlea and presumably in fluid continuity with the cerebrospinal fluid space. Possible clinical implications are discussed.

Cerebellopontine angle tumor composed of Schwann and meningeal proliferations

Tumors found in the cerebellopontine angle are predominantly vestibular schwannomas. Mixed tumors found within the cerebellopontine angle are thought to be exceedingly rare and exclusively associated with neurofibromatosis 2. We report a case of a mixed tumor composed of Schwann and meningeal cell proliferations in a patient who was not diagnosed as having neurofibromatosis 2. Mixed tumors composed of neoplastic Schwann and meningeal cells have rarely been reported. However, new evidence indicates that these mixed tumors may be more common than was previously thought and may have an interrelated mechanism of pathogenesis. Although the case we describe does not fulfill the current diagnostic criteria for neurofibromatosis 2, a presumptive diagnosis was given, suggesting that the current diagnostic criteria for neurofibromatosis 2 may be too narrow.

Histopathology of cochlear implants in humans

The insertion of an intrascalar electrode array during cochlear implantation causes immediate damage to the inner ear and may result in delayed onset of additional damage that may interfere with neuronal stimulation. To date, there have been reports on fewer than 50 temporal bone specimens from patients who had undergone implantation during life. The majority of these were single-channel implants, whereas the majority of implants inserted today are multichannel systems. This report presents the histopathologic findings in temporal bones from 8 individuals who in life had undergone multichannel cochlear implantation, with particular attention to the type and location of trauma and to long-term changes within the cochlea. The effect of these changes on spiral ganglion cell counts and the correlation between speech comprehension and spiral ganglion cell counts were calculated. In 4 of the 8 cases, the opposite, unimplanted ear was available for comparison. In 3 of the 4 cases, there was no significant difference between the spiral ganglion cell counts on the implanted and unimplanted sides. In addition, in this series of 8 cases, there was an apparent negative correlation between residual spiral ganglion cell count and hearing performance during life as measured by single-syllable word recognition. This finding suggests that abnormalities in the central auditory pathways are at least as important as spiral ganglion cell loss in limiting the performance of implant users.

Conservative management of infections in cochlear implant recipients

OBJECTIVE

The goal of this study was to evaluate a conservative management strategy of postoperative infection after cochlear implantation.

METHODS

A retrospective review of the medical records of 108 cochlear implant patients operated on at the University of California, San Francisco between 1991 and 2000 and 133 cochlear implant patients from the University of Iowa between 1997 and 2000 showed 4 patients with evidence of postoperative infections. The clinical presentation, intervention, laboratory results, and outcome are analyzed in each case.

RESULTS

Minimal surgical intervention with limited incision and drainage with prolonged postoperative antibiotics was effective in treating postoperative cochlear implant infections without the need for device removal. Implant function remained unaffected after surgery.

CONCLUSION

Postoperative cochlear implant infections can be effectively controlled with limited surgical and prolonged medical management. Chronic implant infections may be explained by a primary immunodeficiency. With appropriate treatment leading to infection control, a conservative management strategy is advocated before consideration of device explantation.

Acoustic Neuromas in the Elderly

OBJECTIVE

To determine if an "observation" protocol with serial scanning is a safe and effective management paradigm for acoustic neuromas in the elderly.

STUDY DESIGN

A retrospective case review was performed.

SETTING

This study was performed in an academic, tertiary care center.

PATIENTS

Forty-one patients over the age of 65 years were identified with the primary diagnosis of unilateral acoustic neuroma, without prior treatment or observation.

INTERVENTION

The patients were followed with serial, gadolinium-enhanced magnetic resonance imaging (MRI) scans performed at 6 months and then yearly, if no significant growth occurred.

MAIN OUTCOME MEASURES

The patients were monitored for tumor growth, cranial nerve deficits, and hydrocephalus.

RESULTS

The patients were followed for an average of 3.5 years (range, 6 months to 9 years). The average tumor size at presentation was 1.14 cm, with a range of growth rates from 0 to 1.2 cm per year. Twenty-one patients demonstrated tumor growth at an average rate of 0.322 cm per year. Only five patients (12%) required further intervention. Three patients underwent translabyrinthine excision, and two patients were treated with radiation. No patients developed significant complications during the observation period.

CONCLUSIONS

Acoustic neuromas in the older population can be managed safely using serial MRI scanning. No correlation could be made between initial tumor size and subsequent growth rate.

Electrically evoked compound action potentials recorded from subjects who use the nucleus CI24M device

The ability to directly measure the response to a pulse with the NRT opens the possibility of using this system to characterize the responses to more complex stimuli. An example is the responses to constant-amplitude pulse trains. With further changes in the software that controls the implant, it may be possible to characterize the responses to modulated pulse trains or other stimuli that better approximate the type of stimuli that are normally used with a cochlear implant speech processor.

Language and reading acquisition in children with and without cochlear implants

These data provide a coherent view of the spoken language and reading skills of children receiving cochlear implants. The data reveal both spoken language gains and clear benefit to these children with regard to reading. Improvement in reading is consistent with predictions based on prior research demonstrating a strong association between spoken language and reading. An intervention such as a cochlear implant has a direct effect on spoken language, and this can subsequently affect reading performance. This provides some of the first experimental evidence supporting the causal relationship between spoken language and reading.

Facial nerve grafts: from cerebellopontine angle and beyond

OBJECTIVES

To review the outcomes from facial nerve cable grafting in a variety of pathologic conditions and to determine the possible causes of poor facial function after facial nerve grafting.

STUDY DESIGN

A retrospective review of patients undergoing facial nerve grafts through a neurotologic procedure.

SETTING

This study was performed at a university-based tertiary referral center.

PATIENTS

All 27 patients undergoing a neurotologic procedure that required a facial nerve graft from 1982 to 1997 were reviewed. Fourteen patients had grafts from the facial nerve stump at the brainstem.

INTERVENTIONS

All patients had facial nerve function determined by the senior neurotologist and through use of historical data and photographs.

MAIN OUTCOME MEASURE

A facial nerve repair recovery score was developed for facial nerve transection and repair. The House-Brackmann scale was found to be inappropriate for transected and repaired nerves.

RESULTS

Facial function was found in 23/25 (92%) patients with at least 8 months follow-up. Statistical analysis revealed no significant correlation between graft length and recovery score. Patients who had the nerve grafted to a site distal to the meatal foramen had a mean outcome that was nearly one grade level better than those with an anastomosis proximal to the meatal foramen (i.e., at the brainstem), but this did not reach statistical significance.

CONCLUSIONS

Facial nerve grafting is an effective way of restoring facial motor function. A new facial recovery grading scale is proposed for repaired or grafted facial nerves.

Surgical management of Bell's palsy

OBJECTIVES

Incomplete return of facial motor function and synkinesis continue to be long-term sequelae in some patients with Bell's palsy. The aim of this report is to describe a prospective study in which a well-defined surgical decompression of the facial nerve was performed in a population of patients with Bell's palsy who exhibit the electrophysiologic features associated with poor outcomes. In addition, management issues related to Bell's palsy including herpes simplex virus typel etiology, the natural history, electrodiagnostic testing, and efficacy of surgical strategies are reviewed.

STUDY DESIGN AND METHODS

A multicenter prospective clinical trial was designed utilizing electroneurography (ENOG) and voluntary electromyography (EMG) to identify patients with Bell's palsy who would most likely develop poor return of facial function, as suggested by Fisch and Esslen. Patients who displayed electrodiagnostic features of poor outcome, >90% degeneration on ENOG testing and no voluntary motor unit EMG potentials within 14 days of onset of total paralysis, were offered a surgical decompression of the facial nerve through a middle cranial fossa surgical exposure, including the tympanic segment, geniculate ganglion, labyrinthine segment, and meatal foramen. Control subjects were those who displayed similar electrodiagnostic features and time course.

RESULTS

Subjects who did not reach 90% degeneration on ENOG within 14 days of paralysis all returned to House-Brackmann grade I (n = 48) or II (n = 6) at 7 months after onset of the paralysis. Control subjects self-selecting not to undergo surgical decompression when >90% degeneration on ENOG and no motor unit potentials on EMG were identified had a 58% chance of developing a poor outcome at 7 months after onset of paralysis (House-Brackmann grade III or IV [n = 19]). A group with similar ENOG and EMG findings undergoing middle fossa facial nerve decompression exhibited House-Brackmann grade I (n = 14) or II (n = 17) in 91% of the cases. An exact permutation test confirmed that the surgical group had a significantly higher proportion of patients with a good outcome (House-Brackmann grade I or II) (P = .0002).

CONCLUSION

Electroneurography in combination with voluntary EMG successfully identified patients who will most likely return to normal from those who had a greater chance of long-term sequelae from Bell's palsy. Surgical decompression medial to the geniculate ganglion significantly improves the chances of normal or near-normal return of facial function in the group that has a high probability of a poor result. Surgical decompression must be performed within 2 weeks of onset of total paralysis for it to be effective.

Residual speech recognition and cochlear implant performance: effects of implantation criteria

OBJECTIVE

This study aimed to determine the effects of preoperative speech reception on postoperative speech recognition with a cochlear implant and to develop a statistical index allowing prediction of postoperative speech recognition before implantation.

STUDY DESIGN

The study design was a retrospective case review with statistical modeling.

SETTING

The study was conducted at a tertiary referral center with an associated Veteran's Administration hospital.

PATIENTS

Postlingually deafened adults with and without residual speech reception participated.

INTERVENTION

Cochlear implantation with Cochlear Corporation CI-22 and CI-24 devices was performed.

MAIN OUTCOME MEASURES

Monosyllabic word recognition was measured.

RESULTS

Duration of deafness and preoperative sentence recognition are both significant predictors of word recognition with a cochlear implant and can account for 80% of the variance in word recognition.

CONCLUSIONS

Cochlear implant outcomes are variable but predictable within specific ranges.

Sensorineural hearing loss after occlusion of the enlarged vestibular aqueduct

OBJECTIVE

This study aimed to report the hearing results of endolymphatic sac occlusion in patients with enlarged vestibular aqueduct syndrome.

STUDY DESIGN

The study design was a multiinstitutional retrospective case series.

SETTING

The study was conducted at tertiary otologic referral centers.

PATIENTS

The study included 10 previously unreported patients with progressive sensorineural hearing loss and vestibular aqueducts greater than 1.5 mm in diameter on computerized tomography.

INTERVENTION

Occlusion of the enlarged vestibular aqueduct was performed by means of a transmastoid surgical approach. Either intraluminal endolymphatic sac obliteration (five patients) or extraluminal extradural endolymphatic sac obliteration (five patients) was accomplished with temporalis fascia.

MAIN OUTCOME MEASURES

The postoperative pure tone average (PTA) and speech discrimination scores were compared with the preoperative levels using conventional audiometry.

RESULTS

Nine of 10 patients experienced some degree of sensorineural hearing loss. The median change in PTA was a loss of 21 decibels (dB), and 50% of the patients experienced a sensorineural hearing loss greater than 25 dB. Postoperative change in PTA ranged from +10 dB to -59 dB. The median change in speech discrimination score was a loss of 27.5%. Only one patient had an improvement in both speech discrimination score and pure tone averages after surgery. Patients who underwent extraluminal occlusion had a median PTA loss of 12 dB, and patients who underwent open sac occlusion had a median PTA loss of 34 dB. These were not statistically different.

CONCLUSION

In this series of 10 patients, 5 had a greater than 25 dB decrease in hearing after occlusion of the enlarged vestibular aqueduct. Surgical occlusion of the enlarged vestibular aqueduct showed no significant benefit in hearing preservation. The otologic surgeon is alerted to the potential for severe sensiorineural hearing loss after occlusion of the enlarged vestibular aqueduct.

Surgical technique for the CLARION cochlear implant

This paper describes a technique for implantation of the CLARION Multi-Strategy Cochlear Implant based upon the authors' surgical experience with the device. Although much of the procedure is similar to many commonly performed otologic operations, including implantation of other cochlear prostheses, several device-specific modifications are highlighted. Those modifications include a substantial bony seat, facial recess, and cochleostomy, and the use of an electrode insertion tool.

Management of cochlear implant infections

OBJECTIVE

The aim of this study was to illustrate and discuss management of cochlear implant infections.

STUDY DESIGN

The study design was a retrospective case review.

SETTING

This study was performed at a tertiary referral center with an associated Veterans Administration Hospital.

PATIENTS

Postlingually deafened adults who had revision surgery for delayed cochlear implant infections were included in this study.

INTERVENTION

Medical and surgical management of device infection without explantation.

MAIN OUTCOME MEASURES

Eradication of infection without loss of speech reception.

RESULTS

All four patients were successfully managed without explantation.

CONCLUSIONS

Explantation of an infected but functioning multichannel implant is not mandatory in the absence of systemic sepsis.

Speech perception performance in experienced cochlear-implant patients receiving the SPEAK processing strategy in the Nucleus Spectra-22 cochlear implant

Sixteen experienced cochlear implant patients with a wide range of speech-perception abilities received the SPEAK processing strategy in the Nucleus Spectra-22 cochlear implant. Speech perception was assessed in quiet and in noise with SPEAK and with the patients' previous strategies (for most, Multipeak) at the study onset, as well as after using SPEAK for 6 months. Comparisons were made within and across the two test sessions to elucidate possible learning effects. Patients were also asked to rate the strategies on seven speech recognition and sound quality scales. After 6 months' experience with SPEAK, patients showed significantly improved mean performance on a range of speech recognition measures in quiet and noise. When mean subjective ratings were compared over time there were no significant differences noted between strategies. However, many individuals rated the SPEAK strategy better for two or more of the seven subjective measures. Ratings for "appreciation of music" and "quality of my own voice" in particular were generally higher for SPEAK. Improvements were realized by patients with a wide range of speech perception abilities, including those with little or no open-set speech recognition.

Single-channel to multichannel conversions in adult cochlear implant subjects

OBJECTIVE

This study aimed to compare open-set speech perception of single-channel with multichannel cochlear implants in the same ear of postlingually deafened adults.

STUDY DESIGN

The study design was a retrospective case and literature review.

SETTING

The study was conducted at a tertiary referral center with an associated veterans administration hospital.

PATIENTS

Postlingually deafened adults with at least 6 months of experience with a single-channel cochlear implant were studied.

INTERVENTION

Replacement of a single-channel with a multichannel cochlear implant in the same ear was performed.

MAIN OUTCOME MEASURES

Open-set word and sentence perception scores at least 6 months after single-channel implantation and multichannel reimplantation were measured.

RESULTS

Six of six patients had substantial improvement in open-set speech recognition after reimplantation of the same ear.

CONCLUSIONS

Removal of a functioning single-channel implant and replacement with a multichannel device are appropriate in postlingually deafened adults who desire better speech recognition.

Psychological change over 54 months of cochlear implant use

OBJECTIVE

To determine the long-term psychological outcome of postlingually deafened adults who received multichannel cochlear implants and to relate the psychological outcome to audiological outcome.

DESIGN

Thirty-seven recipients of multichannel cochlear implants who participated in a prospective clinical trial completed psychological assessments before implantation and at regularly scheduled follow-ups through 54 mo of implant use. Standardized measures of affect, social function, and personality were used, and scores on these measures were correlated with asymptotic scores on several audiological measures.

RESULTS

Evidence of significant improvement on measures of loneliness, social anxiety, and distress were obtained within a year after implantation and throughout the duration of the follow-up period. For measures of assertiveness and marital satisfaction, improvement was apparent only after long-term implant use. Although favorable changes on the Minnesota Multiphasic Personality Inventory (MMPI) Depression Scale were evidenced only in the initial follow-up period, improvements on the MMPI Paranoia and Social Introversion Scales persisted throughout the 54 mo follow-up.

CONCLUSION

Multichannel cochlear implant use is associated with long-term psychological benefit. Correlations between audiological outcome and psychological outcome, however, suggested that the relation between audiological benefit and psychological benefit is not simple.

Preliminary experience with neural response telemetry in the nucleus CI24M cochlear implant

OBJECTIVE

This study aimed to compare recordings of the electrically evoked whole nerve action potential (EAP) made using the reverse telemetry system of the Nucleus CI24M device with those recorded from individuals who use the Ineraid cochlear implant system.

STUDY DESIGN

Data were collected in a prospective fashion from Nucleus CI24M cochlear implant users and compared with retrospective data collected from patients who use the Ineraid device.

SETTING

All data were collected at the Department of Otolaryngology-Head and Neck Surgery, University of Iowa Hospitals and Clinics.

PATIENTS

Data are reported from 8 patients who use the Nucleus CI24M cochlear implant and 20 patients who use the Ineraid cochlear implant system.

INTERVENTIONS

The interventions described in this study were diagnostic in nature.

MAIN OUTCOME MEASURES

EAP growth and refractory recovery data are reported. EAP thresholds recorded from patients who use the Nucleus CI24M device also are compared with behavioral thresholds for the stimulus used to evoke the EAP as well as the stimulation levels needed to program the speech processor.

RESULTS

EAP morphology, growth, and refractory recovery functions recorded using the Nucleus CI24M reverse telemetry system compared favorably with similar measures recorded from Ineraid cochlear implant users.

CONCLUSIONS

Reasonable EAP responses can be recorded using the Nucleus CI24M device. More data are needed to determine whether the information about neural responsiveness available with this device will be clinically useful.

Cartilage reconstruction of the scutum defects in canal wall up mastoidectomies

PURPOSE

This study was performed to evaluate whether cartilage reconstruction of scutal wall defects diminishes retraction pocket and recurrent cholesteatoma, as compared with no cartilage reconstruction of the scutal defect.

MATERIALS AND METHODS

A retrospective chart review from 1980 to 1993 was performed on all patients undergoing a canal wall up mastoidectomy. These procedures were done in a large teaching hospital where some surgeons reconstructed with cartilage and others did not. The recurrence rate of cholesteatoma and retraction pockets, as well as the need for further surgery, was assessed.

RESULTS

There were 103 canal wall up mastoidectomies performed, and 84 patients were available for long term follow-up. Of these, 52 were not reconstructed with cartilage, whereas 32 were reconstructed with cartilage. Of the 52 patients not reconstructed, 47% did not develop retraction pockets. Of the 53% who did develop a retraction pocket, only one third required further surgery, and the others were managed in the office. Of the 32 patients that were reconstructed with cartilage, 66% did not develop further retractions. Of the 34% who did develop a retraction pocket, one third required further surgery. In both groups, those who did require further surgery did have recurrent cholesteatoma as well.

CONCLUSION

It would appear that reconstruction of scutal wall defects after canal wall up mastoidectomies with cartilage may be of some benefit in preventing further retraction pockets and thus the recurrence of cholesteatoma.

Performance of 2- and 3-year-old children and prediction of 4-year from 1-year performance

OBJECTIVE

To examine whether children perform better when they receive cochlear implants when they are 2 to 4 years of age than when they are older, and to determine whether 4-year performance can be predicted from 1-year results.

METHOD

Children in two age groups (2 to 4, 4 to 9 years) were tested for performance, and the age groups were compared. Children were also tested 1 and 4 years after implantation.

RESULTS

The results suggest that the "implanted young" group scored higher than the "implanted old" group after 36 months, and that 1-year performance is helpful in predicting 4-year performance.

CONCLUSION

It may be desirable for children to undergo implantation when they are under 2 years of age, provided that appropriate selection criteria can be determined.

Speech perception by prelingually deaf children and postlingually deaf adults with cochlear implant

We review recent data from the University of Iowa obtained from prelingually deaf children over 3 years using feature-extraction versions of the Nucleus cochlear implant, and from postlingually deaf adults using the compressed-analog Ineraid, a feature-extraction version of Nucleus, and a continuous interleaved sampling version of the Clarion cochlear implant. Both adults and children were followed over a 3-year period. Average results are shown where each patient is represented at each point in time. Results for the children show continued improvement over the 3-year period, with some children obtaining maximum scores possible on the easier closed-set tests. Substantial improvements in audiovisual enhancement were provided by the cochlear implant. Results from the adults show maximum gains within the first year of implant use, although some patients show continued improvements after 2 years of implant use. Adults who have been deaf for several years and who receive their implant when they are older tend not to perform as well as adults who have been deaf for only a few years or receive their implant when they are younger.

Speech perception by prelingually deaf children using cochlear implants

In this investigation we measured the performance of 50 prelingually deaf children on several speech perception tests. Children were from 2 to 15 years of age, and some children were tested with as much as 5 years of cochlear implant use. Speech perception tests included the recognition of stress pattern, consonants, vowels, words, and sentences. The audiovisual perception of consonants was also measured. Average results indicated that gains were being made in the perception of stress and words in a closed-set context within 1 year from implantation. The perception of words in an open-set context demonstrated much slower increases over time. Large individual differences were observed. Some preliminary data suggest that children who receive implants before the age of 4 years obtain higher scores, on average, than children who receive implants after the age of 5 years. Some children become part-time users or nonusers of their cochlear implants. The average results from 18 congenitally deaf children were significantly higher than the average results from 12 children with prelingually acquired deafness after 3 years of implant use. Information on vowel and consonant features shows increases in performance after 2 years of cochlear implant use, with the exception of the place feature. For this feature, no changes were observed. Vision-alone testing indicated that lipreading performance increased over time. An audiovisual enhancement provided by the cochlear implant was observed for all features.

Performance over time of adult patients using the Ineraid or nucleus cochlear implant

This study examined the average and individual performance over time of 49 adult cochlear implant subjects. Subjects were randomly assigned to receive either the Ineraid cochlear implant, with analog processing, or the Nucleus cochlear implant, with feature-extraction processing. All subjects had postlingual profound bilateral sensorineural hearing loss and received no significant benefit from hearing aids before implantation. Group data were examined in two ways. First, only subjects who had complete data over the test period were examined. Second, an analysis of all available data was carried out by mixed linear-model analysis. In this analysis, to account for missed follow-ups at the planned intervals, data consisting of the observations closest in time to the planned test times were modeled by natural splines with knots at the planned follow-up times. Contrasts between all pairs of planned follow-up times for each device were tested, as were contrasts between devices at each planned follow-up time. Results indicated little difference between the performance of the Ineraid and Nucleus subjects in their level of performance or their rate of learning. Postimplantation performance was typically superior to preimplantation performance within 9 months, and continued to improve up to 18-30 months depending on the speech perception measure. In some subjects, improvements in speech perception measures were observed up to four or five years postimplantation. There was also evidence that three subjects had a decrement in overall speech perception performance, although their postimplantation scores were always higher than their preimplantation scores. In at least one subjects this was likely a result of age-related cognition decrements.

Cochlear implant use by prelingually deafened children: the influences of age at implant and length of device use

This study focused on long-term speech perception performances of 34 prelingually deafened children who received multichannel cochlear implants manufactured by Cochlear Corporation. The children were grouped by the age at which they received cochlear implants and were characterized by the amount of time they used their device per day. A variety of speech perception tests were administered to the children at annual intervals following the connection of the external implant hardware. No significant differences in performance are evident for children implanted before age 5 compared to children implanted after age 5 on closed-set tests of speech perception ability. All children demonstrated an improvement in performance compared to the pre-operative condition. Open-set word recognition performance is significantly better for children implanted before age 5 compared to children implanted after age 5 at the 36-month test interval and the 48-month test interval. User status, defined by the amount of daily use of the implant, significantly affects all measures of speech perception performance except pattern perception.

Appropriateness of magnetic resonance imaging in sudden sensorineural hearing loss

Idiopathic sudden sensorineural hearing loss is an enigmatic condition of unknown cause. Although the treatment for sudden sensorineural hearing loss is controversial, the evaluation for a cause should not be. All patients are evaluated with a complete history, physical examination, audiologic examination, and blood draw to evaluate complete blood count, general chemistry screen, thyroid function test results, erythrocyte sedimentation rate, and fluorescent treponemal antibody absorbance. Magnetic resonance imaging with gadolinium contrast is essential in the evaluation of idiopathic sudden sensorineural hearing loss, even if there is a complete response to either treatment or no treatment. During the last year we treated 16 patients for idiopathic sudden sensorineural hearing loss with our protocol of intravenous dextran/Hypaque or oral high-dose steroids. Fifteen patients were evaluated immediately before treatment with a magnetic resonance imaging scan. An additional patient had been treated successfully with high-dose steroids at an outside institution and came in for an evaluation. Of these 16 patients, 3 (18.75%) were found to have significant pathologic conditions on magnetic resonance imaging scan. The patient who had been treated successfully on the outside was noted to have a 5-mm intracanalicular acoustic neuroma, the second patient was found to have a multiple sclerosis lesion at the level of the superior olive, and the third patient, who had had a normal magnetic resonance imaging scan 18 months previously, was now found to have a large 4- to 5-cm meningioma in the cerebellopontine angle. We believe it is essential that all patients with idiopathic sudden sensorineural hearing loss be evaluated at some point during their treatment with a magnetic resonance imaging scan with gadolinium contrast.

Appropriateness of Magnetic Resonance Imaging in Sudden Sensorineural Hearing Loss

Idiopathic sudden sensorineural hearing loss is an enigmatic condition of unknown cause. Although the treatment for sudden sensorineural hearing loss is controversial, the evaluation for a cause should not be. All patients are evaluated with a complete history, physical examination, audiologic examination, and blood draw to evaluate complete blood count, general chemistry screen, thyroid function test results, erythrocyte sedimentation rate, and fluorescent treponemal antibody absorbance. Magnetic resonance imaging with gadolinium contrast is essential in the evaluation of idiopathic sudden sensorineural hearing loss, even if there is a complete response to either treatment or no treatment. During the last year we treated 16 patients for idiopathic sudden sensorineural hearing loss with our protocol of intravenous dextran/Hypaque or oral high-dose steroids. Fifteen patients were evaluated immediately before treatment with a magnetic resonance imaging scan. An additional patient had been treated successfully with high-dose steroids at an outside institution and came in for an evaluation. Of these 16 patients, 3 (18.75%) were found to have significant pathologic conditions on magnetic resonance imaging scan. The patient who had been treated successfully on the outside was noted to have a 5-mm intracanalicular acoustic neuroma, the second patient was found to have a multiple sclerosis lesion at the level of the superior olive, and the third patient, who had had a normal magnetic resonance imaging scan 18 months previously, was now found to have a large 4- to 5-cm meningioma in the cerebellopontine angle. We believe it is essential that all patients with idiopathic sudden sensorineural hearing loss be evaluated at some point during their treatment with a magnetic resonance imaging scan with gadolinium contrast.

Initial independent results with the Clarion cochlear implant

OBJECTIVE

This paper reports some preliminary findings from patients, implanted at the University of Iowa, using the Advanced Bionics Clarion cochlear implant (version 1.0). We compared the performance of patients using both simultaneous analog and nonsimultaneous pulsatile processing strategies. The performance of Clarion patients was also compared with a group of patients who were using either the feature-extraction Nucleus cochlear implant or the compressed-analog Ineraid cochlear implant.

DESIGN

One aim was to compare the analog and pulsatile stimulation in 19 patients using the Clarion implant. This aim could be accomplished only partially because of difficulties encountered in adequately fitting patients with the analog strategy. A second aim was to compare the Clarion users' performance with feature-extraction Nucleus and compressed-analog Ineraid patients. Comparisons were made with all patients having 9 mo experience postimplantation.

RESULTS

Subjects performed better using the pulsatile mode compared with the analog mode. All subjects chose to use the pulsatile strategy after the first 3 mo of the study. Results comparing performance at 9 mo with our compressed-analog Ineraid and feature-extraction Nucleus patients indicated, in general, better average performance for the Clarion users.

CONCLUSIONS

We conclude that the pulsatile version of the Clarion cochlear implant typically produces superior performance to the analog version of that device at this stage in its development. After 9 mo of experience, users of the Clarion implant are performing better than are users of the feature-extraction Nucleus and compressed-analog Ineraid cochlear implants with comparable amounts of experience.

Results and complications from acoustic neuroma excision via middle cranial fossa approach

The middle cranial fossa (MCF) approach for acoustic neuromas has been criticized for limited exposure, anatomic surgical difficulty, and increased risk to facial nerve and temporal lobe. From 1986 to the present, 49 patients' acoustic neuromas were removed via the MCF approach. Hearing was preserved or improved in 69% of patients regardless of preoperative hearing levels, and facial nerve function was Grade II or better in 94%. Both results demonstrate improvement from our report 8 years ago. In addition, all patients are without recurrence. Our results continue to demonstrate the surgical advantages of the MCF approach and that, in experienced hands, it is as efficacious as other hearing preservation approaches.

A within-subject comparison of adult patients using the Nucleus F0F1F2 and F0F1F2B3B4B5 speech processing strategies

This study compares the Nucleus F0F1F2 and F0F1F2B3B4B5 (also known as "Multipeak") of "Mpeak") processing schemes in 17 patients wearing the Mini Speech Processor. All patients had at least 18 months implant experience using the F0F1F2 processing strategy. For this study, they were switched to the F0F1F2B3B4B5 processing strategy for 3 months. They then returned to using the F0F1F2 strategy for 3 months, then used the F0F1F2B3B4B5 strategy again for 3 months, and lastly used the F0F1F2 strategy for 3 months. Performance' was evaluated with both schemes after each interval, using speech recognition tests and subjective ratings. Overall, differences between the results for the two processing schemes were not large. Average performance was somewhat better for the F0F1F2B3B4B5 strategy for word and sentence identification, but not for any of the other speech measures. Superior performance was observed in 8 patients with the F0F1F2B3B4B5 strategy. However, 6 of the 8 individuals were significantly better on only one of the six speech measures in the test battery. The other 2 patients performed better on two of the speech measures. Superior performance was also observed in 3 patients with F0F1F2 strategy for consonant recognition. For the remaining patients, there was little difference in their performance with the two strategies. Information transmission analyses indicated that the F0F1F2B3B4B5 strategy transmitted consonant duration and frication cues more efficiently than F0F1F2. Experience with one strategy appeared to benefit performance with the other strategy.

Systematic Approach to Electrode Insertion in the Ossified Cochlea

Ossification of the fluid spaces of the cochlea occurs often in candidates for cochlear implantation, especially children. When noted before surgery on computerized tomography, ossification previously was thought to contraindicate cochlear implantation because of possible mechanical obstruction and uncertainty about the level of function that could be achieved by stimulating an ossified cochlea. However, during the preceding 6 years, techniques have been developed that permit implantation in ossified cochleas. We present a systematic approach that has been developed to treat the three clinically important categories of cochlear ossification: round window niche obliteration, inferior segment obstruction, and upper segment obstruction. Case reports are presented for each of these three drill-out procedures, demonstrating results often similar to those expected for implantation of the nonossified cochlea.

Medullary carcinoma of the thyroid metastatic to the temporal bone

We report a case of proven thyroid medullary carcinoma, metastatic to the temporal bone. Review of the otolaryngology literature demonstrates that this is the first such report. The patient presented with symptoms, physical examination, and imaging studies suggestive of a glomus jugulare tumour. The pre-operative diagnosis of metastatic thyroid medullary carcinoma, however, was made, based on a history of medullary carcinoma of the thyroid with previous metastases as well as an elevation in calcitonin levels. Histological examination of the surgical specimen confirmed the diagnosis.

Longitudinal assessment of physiological and psychophysical measures in cochlear implant users

OBJECTIVE

The purpose of this study was to evaluate the effects of long-term electrical stimulation on human cochlear implant users.

DESIGN

Repeated measures of electrically evoked auditory brain steam response (EABR) threshold, slope of the EABR growth function, and behavioral measures of threshold and dynamic range were made for a group of 22 Ineraid cochlear implant users and 19 Nucleus cochlear implant users over a 3- to 5-yr period.

RESULTS

Data from both Ineraid and Nucleus cochlear implant users suggest that EABR threshold, slope of the EABR growth function, and behavioral measures of threshold and dynamic range remain reasonably stable for periods up to 5 yr postimplant.

CONCLUSIONS

The results of this study show little evidence that prolonged electrical stimulation through daily use of a cochlear implant has deleterious effects on the auditory system.

Preliminary results with the Clarion cochlear implant in postlingually deaf adults

A clinical trial of three different multichannel cochlear implants is in progress at The University of Iowa. Fifty postlingually deaf adults participated in a prospective randomized study of the Nucleus implant and the Ineraid device. Subsequently, 23 consecutive postlingually deaf adults have been implanted with the Clarion system. The speech perception performance obtained after 9 months of implant use with all devices was compared. In addition, Clarion patient results at 9 months were compared with long-term (36 months) results from subjects using the other two multichannel implants. Preliminary speech perception scores on the Iowa sentence test (sound-only) and NU-6 words (sound-only) demonstrate that the Clarion subjects, as a group, perform at higher levels than subjects using the other two systems. A wide range of performance is observed with all devices. The continuous interleaved pulsatile strategy of the Clarion device appears to be advantageous for this group of subjects.

Anatomical and physiological measures of auditory system in mice with peripheral myelin deficiency

Animal models with genetic abnormalities have been increasingly used in auditory research. Both TrJ mice and Po-DT-A mice are animals with peripheral myelin deficiency. In TrJ mice, the defect is due to a mutated PMP-22 gene. In Po-DT-A mice, the defect is produced by a transgene using the rat Po promotor to direct the expression of gene encoding for the bacterial diphtherial toxin A chain (DT-A). This study evaluates the auditory system both physiologically and histologically in these two strains of mice. Histological examination revealed that there was myelin deficiency of the auditory nerve fibers, accompanied by a loss of dendrites and a loss of spiral ganglion cell bodies in both strains of mice. In general, histological deficits in TrJ mice were greater than those in Po-DT-A mice. There was a strong correlation between the degree of myelin deficiency and the survival of spiral ganglion neurons. ABR measurements exhibited differences in threshold, latency and slope of the ABR growth function between myelin-deficient mice and their respective controls. These results suggest that the integrity of the myelin in the auditory nerve is important both for neural survival and for normal electrophysiological function of spiral ganglion neurons.

Tinnitus and acoustic neuromas: analysis of the effect of surgical excision on postoperative tinnitus

In this retrospective review of the 160 acoustic neuroma cases treated at The University of Iowa between 1980 and 1991, follow-up information was obtained for 82% by telephone interview. Postoperative tinnitus was a symptom reported by 75% of the acoustic neuroma patients. Overall, among patients with tinnitus preoperatively, the condition postoperatively was absent in 45%, lessened in 17%, unchanged in 30%, and greater in 8%. Detailed results are compared to other series and significant differences in the depth of comparison described.

Performance of adult Ineraid and Nucleus cochlear implant patients after 3.5 years of use

Forty-two postlingually deafened adult patients, 21 with a formant extraction version of the Nucleus cochlear implant and 21 with the Ineraid cochlear implant (analog processing), were evaluated on a series of speech perception tests after using their implants for about 3.5 years. A wide range of performance was observed across patients for both devices. All but 4 patients showed an enhancement in their lipreading ability with the implant. Word recognition averaged about 14-19% correct, and word recognition in sentences averaged about 43-49% correct for the two implant groups. Average performance was superior with the Ineraid implant on consonant recognition in noise. An information transmission analysis suggested that vowel perception was influenced by first- and third-formant frequency for the Nucleus, and first-formant and fundamental frequency for the Ineraid patients. It appeared that the Ineraid device was more effective, on average, at conveying information about consonant nasality and frication. For consonant perception, nasality and frication contributed most to the total information transmitted for both implant types. Both devices had difficulty conveying information about vowel second-formant frequency and consonant place information. These scores at 3.5 years are substantially elevated from preoperative performance and, overall, the patients clearly benefit from their implant.

Diatrizoate and dextran treatment of sudden sensorineural hearing loss

Many treatments have been proposed to manage sudden sensorineural hearing loss. The University of Iowa has used a protocol of intravenous radiopaque contrast and volume expander for the last 10 years in the treatment of sudden sensorineural hearing loss. A retrospective analysis of these cases was performed to review the efficacy of this treatment with respect to the natural history of the disease, as reported in previous studies. Sixty-four percent of 39 cases showed audiometric improvement in their pure-tone averages, speech reception thresholds, and speech discriminations while receiving treatment. Forty-eight percent of these showed improvement after their first treatment doses. Eighty percent of patients who presented more than 7 days after the onset of their hearing loss showed audiometric improvement with treatment, whereas 71 percent of patients presenting before 7 days showed audiometric improvement. However, the patients who presented earlier showed more marked improvement. Speech discrimination with the W-22 word list was a predictor of early recovery. Patients with measurable speech discrimination scores on presentation uniformly improved with treatment, even if their pure-tone average was profound. Our findings were suggestive of a pathophysiologic mechanism for some cases of sensorineural hearing loss for which intravenous contrast is efficacious. Although our findings were far from conclusive in this uncontrolled study, these initial results support the use of these agents in a rigorous clinical trial.