Successful revision of failed cochlear implants in severe labyrinthitis ossificans

Labyrinthitis ossificans may complicate the insertion of a multichannel cochlear implant in patients deafened after meningitis. Two children who initially underwent partial insertion of a 22-channel cochlear implant because of severe cochlear ossification required revision surgery after several months of unsuccessful device use. At the time of revision, resection of the car canal, tympanic membrane, malleus, and incus provided access to the lateral wall of the cochlea, permitting extensive drilling of the basal turn and a circumodiolar placement of the electrode. Functional integrity of the electronic components of the original device was documented intraoperatively, avoiding the expense of a new receiver-stimulator. Complete insertion of the active electrodes was accomplished in both cases, and electrophysiologic responsiveness to the implant was documented using intraoperative electrically evoked auditory brainstem response recordings. Postoperative performance has been similar to that of cochlear implant patients with nonossified ears. Experience with these two cases suggests that efforts to optimize electrode insertion at the original surgical procedure are appropriate and may help to avoid the disappointment of an unsuccessful cochlear implant.

Neonatal choristoma of the tongue containing glial tissue: diagnosis and surgical considerations

There are only six case reports documenting the presence of glial tissue in the tongue. Because of the small number of cases, the presentation and biologic behavior of these lesions is poorly characterized. We present the case of a 10-day-old male infant who arrived at the University of Michigan Medical Center with a history of positional dyspnea, with resultant cyanosis and bradycardia, dysphagia, and a mass at the base of the tongue. Histopathologically, this lesion was initially labeled as a hamartoma, but was ultimately defined as a choristoma based on the exclusive presentation of glial tissue in the specimen. This paper will discuss the presentation, diagnostic evaluation, and therapeutic management of this case. In addition, the role of intraoperative electrodiagnostic monitoring to preserve neuromuscular function will be addressed.

Clinical manifestations of CHARGE Association

The clinical literature regarding CHARGE Association is mostly retrospective in nature and deals largely with non-auditory issues related to the care and management of these patients with multisystem involvements. In this paper, we describe the clinical findings in 24 patients evaluated in the Division of Audiology and Electrophysiology at the University of Michigan Medical Center from 1983 to 1993. We report on the clinical manifestations of CHARGE Association in these patients with particular attention paid to their audiologic status. We discuss the relationships between auditory, ear, and craniofacial anomalies. Our review of these previously unreported cases suggests the following: (1) a variety of audiologic outcomes is possible, however, if a sensorineural or mixed hearing loss exists, it tends to be severe in degree; (2) progressive hearing loss does not appear to occur, but recurring otitis media is a probable confounding factor in the early identification of hearing loss; (3) congenital unresolved facial weakness may serve as a reliable predictor of sensorineural hearing loss; and (4) amplification use may be poor due to a number of factors. We hope to offer guidance to the professionals from assorted disciplines who participate in the care of these children.

Cochlear implantation in patients with cochlear malformations

OBJECTIVE

To report operative findings, postoperative course, and postimplantation performance in patients with cochlear malformations who underwent cochlear implantation.

DESIGN

Case study and intervention study (before-after trial). Minimum follow-up of 12 months; average follow-up of 24 months.

SETTING

Academic tertiary referral center.

PATIENTS

Six patients, including five children who underwent implantation at ages 3.5 to 13 years and one adult who underwent implantation at age 27 years. malformations included common cavity deformity (n = 1), cochlear hypoplasia (n = 2), and incomplete partition (n = 3). All patients with cochlear malformations who underwent implantation at the University of Michigan, Ann Arbor, are included, selected from a group of 196 patients so treated since 1986.

INTERVENTION

Implantation with a standard multichannel cochlear implant.

MAIN OUTCOME MEASURES

Operative findings described include round window and facial nerve anatomy and cerebrospinal fluid leak. Postoperative roentgenographic findings, electrode activation, and reason for non-use of electrodes were investigated. Standard tests of speech perception were used to compare preoperative and postoperative performance for each subject.

RESULTS

Operative findings included round window abnormalities (three patients), anomalous facial nerve (one patient), and cerebrospinal fluid leak (three patients). No surgical complications occurred. A minimum of 10 electrodes were activated for all patients. Electrode thresholds and discomfort levels were variable for several months after implantation. All patients demonstrated improved performance after implantation. Four subjects demonstrated open-set speech perception. Two other subjects, whose poor language skills precluded administration of standard tests, showed increased awareness of environmental sounds and increased vocalization after implantation.

CONCLUSIONS

Cochlear implantation can be a successful method of rehabilitation in patients with congenital deafness who have cochlear malformations.

Cochlear implant device failure: diagnosis and management

Complete, irreversible failure of the implanted receiver-stimulator of the Cochlear Corporation multichannel implant are relatively rare. However, as the implanted patient population grows, malfunctions may be expected. From the over 200 patients implanted at the University of Michigan Medical Center, 6 patients with a complete and irreversible cochlear implant receiver-stimulator failure have been identified and treated. This represents a 3% failure rate. The amount of time between initial implantation and device failure ranged from 6 months to 3.5 years. Determination of device failure was made using psychophysical, electrophysiologic, and averaged electrode voltage measurements. The measurement of the average electrode voltages proved to be useful in determining the condition of the implant. Physiologic changes causing reduced electrical excitability were ruled out using psychophysical or electrophysiologic promontory testing. All patients were successfully explanted and reimplanted.

Electrically evoked auditory brain-stem response in pediatric patients with cochlear implants

OBJECTIVE

To study the feasibility and clinical applicability of preoperative, transtympanic electrically evoked auditory brain-stem response (EABR) in a pediatric patient population with cochlear implants.

DESIGN

A descriptive study using repeated measures analyses of variance to determine if EABR measures were affected by response configuration or cochlear status.

SETTING

The operating room before cochlear implant surgery.

PATIENTS

A population-based sample of 43 patients aged 2.5 to 14.5 years who were candidates for cochlear implantation.

INTERVENTION

Stimuli consisting of brief balanced biphasic current pulses were provided by a transtympanically placed promontory needle electrode; EABR was recorded with subdermal needle electrodes on the forehead and contralateral mastoid.

MAIN OUTCOME MEASURE

Presence or absence of postoperative electrical excitability with a cochlear implant.

RESULTS

Electrically evoked auditory brain-stem responses were available from 41 of the 43 patients tested. Mean EABR threshold was 406.5 microA (SD = 118.1) for 31 patients with patent cochleas and 472 microA (SD = 91) for 10 patients with cochlear ossification. Mean wave V latency at threshold was 4.69 milliseconds (SD = 0.57).

CONCLUSION

Preoperative EABR is an integral component of the preoperative selection process for pediatric patients with cochlear implants.

Stability of hearing preservation following acoustic neuroma surgery

Identification of small acoustic neuromas has become commonplace. Frequently, affected individuals are identified prior to the development of significant hearing loss. Whereas many studies have focused on hearing preservation surgery, few have reported on stability of hearing results after resection of acoustic neuroma. Between 1985 and 1991, 36 patients underwent resection of an acoustic neuroma via a retrosigmoid, internal auditory canal approach with attempted hearing preservation. Hearing was preserved in 24 patients; 17 were available for testing for the present study. Follow-up ranged from 1.5 to 8 years. All patients underwent complete audiologic assessment; most patients also underwent auditory brainstem response testing. There was an average 6 dB increase in pure-tone average between early (1 month) postoperative and long-term postoperative test results. A binomial single subject statistic was used to assess for significant changes in speech recognition scores over time. In two subjects there was a significant decrease; however, speech recognition also improved significantly in two subjects. Five of the 17 subjects demonstrated either a significant (at least 15 dB) increase in pure-tone average or a significant decrease in speech recognition over the time-course of the study. All patients maintained usable hearing. We conclude that long-term hearing preservation is a realistic goal in selected acoustic neuroma operations.

Hearing loss from a bicycle horn

A 39-month-old child with previously documented normal hearing suffered acoustic trauma from a bicycle horn activated at his ear. Six days after the insult, a 4000-Hz 50-dB sensorineural hearing loss was found. This threshold improved to 30 dB HL over 6 months. The horn produces 143 dB peak SPL, a level clearly associated with a high risk for hair cell damage. This case shows the need for regulations limiting sound levels or requiring warning labels on potentially damaging toys and other recreational devices. Had a warning been provided, the parents of this child would not have bought the horn as a toy.

Cochlear wall titanium implants for auditory nerve stimulation

Genetically deaf dalmatian dogs and ototoxically deafened macaque monkeys were implanted with electrodes housed in cochlear wall titanium implants to assess long-term stability, tolerance, and performance. Short-term human implantation, followed by trials of stimulation, was performed in 4 unilaterally deaf patients. In the dog experiments, cochlear wall electrode stimulation produced consistent electrophysiologic thresholds that were higher, by approximately 6 dB, than those obtained with bipolar scala tympani stimulation. Clinical testing revealed electrically evoked middle latency response, auditory brain stem response, and/or behavioral detection responses in 3 of 4 patients, at levels below those for facial nerve activation and pain sensation. Electrode place discrimination studies, with controls for loudness cues, revealed near-perfect discrimination in a monkey subject. Eleven of the 12 animal implants were found to be rigidly fixed in the cochlear bone, with direct contract between bone and implant over 8% to 23% of the implant surface for the 6 implants examined in detail. These results suggest that long-term fixation of titanium cochlear wall implants occurs by virtue of intimate implant-bone contact in restricted areas. This approach to prosthetic stimulation demonstrates encouraging performance characteristics in achieving auditory activation.

The clinical differentiation between vocal cord paralysis and vocal cord fixation using electromyography

With newer techniques for laryngeal intervention, it becomes a practical necessity to understand whether an immobile cord is due to neurogenic dysfunction or cricoarytenoid fixation. An objective test for this differentiation is laryngeal electromyography, which can be done as an office procedure with a minimum of discomfort. Our experience in a clinical setting has shown laryngeal electromyography to be efficient in accurately assessing the neuromuscular status of the intrinsic laryngeal musculature.

Tinnitus suppression following cochlear implantation. A multifactorial investigation

The effects of cochlear implant on loudness, annoyance, daily duration, location, and residual inhibition of tinnitus were evaluated by a closed-ended, quantifiable questionnaire in 33 postlingually deafened patients who had received implants at the University of Michigan, Ann Arbor, between 1986 and 1990. Preoperative tinnitus was present in 85% of patients. A statistical comparison of preoperative vs postoperative loudness and annoyance indicated a significant reduction in both of these complaints postoperatively. Loudness and annoyance were significantly correlated, both preoperatively and postoperatively. Fifteen patients (54%) with preoperative tinnitus demonstrated a loudness decrease of 30% or more; 43% demonstrated an annoyance decrease of 30% or more; and 48% demonstrated a decrease of 30% or more in daily tinnitus duration. Patients who experienced a loudness or annoyance decrease of 30% or more after implantation demonstrated significantly higher preoperative levels of these complaints, suggesting that degree of tinnitus reduction after implantation may be related to preoperative loudness and annoyance levels. Contralateral tinnitus suppression was reported by 42% of patients. Residual inhibition ranging from 60 seconds to several hours was reported by 50% of patients, predominantly in the ear with the implant. Age, gender, cause of hearing loss, duration of tinnitus, cochlear implant usage, and time after implantation were not predictive of tinnitus suppression. Overall, the majority of the patients (74%) thought that their cochlear implant was helpful in tinnitus suppression, especially in the ear with the implant. Contralateral residual inhibition and tinnitus suppression suggest a central mechanism contributing to these phenomena.

A comparison of round-window and transtympanic promontory electric stimulation in cochlear implant candidates

We compared within-subjects electrical thresholds and dynamic ranges obtained with direct round-window and transtympanic promontory stimulation carried out preoperatively in 12 patients who were candidates for a cochlear implant. Square waves with frequencies of 50, 100, 200, and 400 Hz were delivered in a 50% duty cycle to both sites in each patient. With the exception of threshold at 50 Hz (promontory thresholds were lower than round-window thresholds), there were no statistically significant differences for either thresholds or dynamic ranges between the two sites of stimulation. There was a general trend for round-window thresholds to be lower and dynamic ranges larger, especially for the higher frequencies of stimulation. Mean threshold slopes for the two sites of stimulation were nearly identical.

Devices for the hearing impaired

Hearing loss can result in significant communicative and social dysfunction. Various methods of sound amplification are available for the hearing impaired. Hearing aids are becoming more technologically sophisticated, more cosmetically appealing and more commonly used. The choice of hearing aid must be individualized and depends on several factors, including the type of hearing loss, the cost of the device, the patient's work environment, motivation and vanity, and the degree of difficulty in using the hearing aid. Devices are also available to help hearing-impaired persons in specific situations where hearing aids may not be necessary. The cochlear implant is a relatively new device for use in the profoundly hearing impaired.

Auditory performance of children with cochlear ossification and partial implant insertion

The management of the profoundly deaf child with a cochlear implant poses a special challenge, particularly when total ossification of the cochlea is present. In this setting, insertion of an electrode array into a child's cochlea is often difficult. Our experience supports the feasibility of partial insertion of a multichannel implant into the basal turn of an ossified cochlea. Five children with ossified cochleae who had undergone partial implantation of a multichannel electrode were compared with the performance of matched controls who had full insertion of multichannel implants. No dramatic differences were detected during a 6- to 18-month follow-up period on selected test measures. These preliminary results suggest that active electrode number may exert a limited effect on performance with a cochlear implant. Drilling out the basal turn of an ossified cochlea in conjunction with partial insertion of a multichannel implant appears to be an acceptable surgical and rehabilitational alternative for placement of a cochlear implant prosthesis in children with complete cochlear ossification.

Prognostic value of evoked and standard electromyography in acute facial paralysis

Ninety-one patients with idiopathic (n = 62) and traumatic (n = 29) facial paralyses were available for evaluation at least 1 year after the onset of paralysis. In nine cases of idiopathic paralysis and in 12 cases of traumatic paralysis, total intratemporal nerve decompression was performed. The remaining patients were treated with steroids alone. All patients underwent evoked electromyography (EEMG) testing within 2 weeks of the onset of paralysis. Facial nerve recovery was graded using the House-Brackmann facial nerve recovery scale. Subjects were grouped according to maximal decline of compound muscle action potential (CAP), as determined by EEMG, and by level of recovery 1 year after onset of paralysis. Among patients who did not undergo surgical decompression of the facial nerve, incomplete clinical recovery (grade III or higher) was significantly associated with CAP decline of greater than 90% (p less than 0.05) for idiopathic paralysis. In contrast, there was no significant association between CAP decline of greater than 90% and clinical outcome in traumatic paralysis. These findings support previous reports of the prognostic value of EEMG in idiopathic facial paralysis, but suggest that this test may have less predictive value in the evaluation of facial paralysis as a result of trauma.

Effects of channel number and place of stimulation on performance with the Cochlear Corporation multichannel implant

The effects of active channel number and place of stimulation on auditory-only performance with the Cochlear Corporation multichannel cochlear implant were investigated in seven subjects. A balanced crossover design was employed; subjects were initially programmed with either 10 basal or the full complement of 20 to 21 active electrodes. Following a 6-month period with the initial coding strategy, subjects were programmed with the alternate configuration, which they used for an additional 6 months. Auditory-only performance on suprasegmental, phoneme (vowel and consonant) open- and closed-set speech recognition was compared between the two electrode configurations. Additionally, performance with the first configuration and performance with the second configuration 3 days following programming were also compared. While a trend for increased scores was noted with 20 electrodes, especially with open-set speech recognition tasks, none of the differences between the two configurations reached statistical significance, as indicated by a Wilcoxon test. A comparison of performance at the end of the first 6-month period and 3 days following programming with the second configuration revealed a trend for reduced scores, especially on vowel tests. Overall, our results indicate that the feature extraction coding strategy associated with the Cochlear Corporation device allows patients to function well with only 10 basal electrodes and that speech recognition is only mildly affected initially when patients are programmed with a different encoding strategy.

Effects of preoperative electrical stimulability and historical factors on performance with multichannel cochlear implant

We investigated the relationship between results of preoperative transtympanic electrical promontory stimulation, duration of deafness, postoperative implanted psychophysical results, and postoperative speech and speech sound recognition as indicated by a battery of five tests. Our subjects were 10 patients implanted with the Cochlear Corporation multielectrode implant, 1 year postimplantation, with a minimum of 17 active electrodes programmed in the bipolar + 1 mode. The results indicated that preoperative promontory thresholds, the slope of the threshold function, and the duration of auditory deprivation are excellent predictors of postoperative speech and speech sound recognition in the auditory (processor alone) mode. These results have significant implications for patient selection and counseling.

Tinnitus as a function of duration and etiology: counselling implications

Based on the data of 528 tinnitus patients, information is presented concerning: (a) conditions and/or activities that affect tinnitus severity, (b) tinnitus symptoms as a function of etiology, and (c) changes in tinnitus symptoms as a function of time since onset. The four most common conditions and/or activities that reduce tinnitus severity were sleep, listening to TV/radio, being in noise, or being in quiet. Many conditions and/or activities increased tinnitus severity. The most common detrimental activities and/or conditions were noise exposure, being in a quiet place, emotional stress, loss of sleep, and physical exhaustion. Results also revealed that tinnitus loudness and severity increased as a function of years since onset. However, tinnitus pitch tended to remain stable. Meniere's patients experienced more annoyance, depression, and interference with sleep and also reported louder tinnitus than other etiologies. Tinnitus counselling should include: (a) informing patients that it is unlikely tinnitus annoyance will change dramatically, (b) alerting patients to the usefulness of tinnitus self-help groups, (c) helping patients to minimize time spent in activities and/or conditions where tinnitus severity is increased and to maximize time in activities and/or conditions where tinnitus severity is decreased, and (d) stressing the avoidance of noise exposure because of the relationship between noise-induced hearing loss and tinnitus.

Cochlear implants in children

The resources and areas of expertise necessary to establish and maintain a successful children's cochlear implant program is discussed. Insights based on experience with a pediatric patient population are presented.

Electrical stimulation of the auditory system after labyrinthectomy

For many years labyrinthectomy has been used as a reliable surgical treatment for patients with unilateral nonserviceable hearing associated with episodic vertigo. In view of the rehabilitative potential of the cochlear implant, the role of labyrinthectomy has been questioned because of a concern to preserve structures of the auditory periphery. However, recent reports demonstrate substantial survival of spiral ganglion cells after labyrinthectomy, suggesting that such patients might be candidates for rehabilitation with cochlear implants if necessary. To address this question from a physiologic approach, we investigated the electrical stimulability of the operated ear in patients who underwent transmastoid labyrinthectomy for the management of vertigo. Ten patients were studied intraoperatively with electrically evoked middle latency response (MLR) potentials. Six of these patients were studied between 3 and 15 months postoperatively via transtympanic stimulation. Postoperatively all patients demonstrated an excitable auditory periphery and behavioral thresholds were similar to intraoperative electrophysiologic thresholds for the same stimuli. These results suggest the persistence of excitable auditory neural elements following labyrinthectomy.

Arytenoid subluxation: diagnosis and treatment

Both arytenoid subluxation and recurrent laryngeal nerve paralysis (RLNP) may result from injury to the larynx, and they may be difficult to distinguish clinically. A patient with arytenoid subluxation who was initially believed to have RLNP was treated with medialization laryngoplasty 1 year after the injury. Preoperative magnetic resonance imaging and computed tomography effectively demonstrated the cricoarytenoid subluxation, which was confirmed by intraoperative electromyography (EMG) showing normal electrical activity in the thyroarytenoid muscle. Photographs from preoperative fiberoptic laryngoscopy are presented to identify the appearance of arytenoid subluxation. Computed tomographic findings and photographs from laryngoscopy of two patients with RLNP documented by intraoperative EMG evaluation are presented to help distinguish the clinical appearance of this disorder from arytenoid subluxation. An integrated approach to the diagnosis and treatment of arytenoid subluxation is presented.

Asymmetric brain stem auditory evoked responses in infants treated with extracorporeal membrane oxygenation

Brain stem auditory evoked responses (BAERs) were obtained in 25 infants who received extracorporeal membrane oxygenation (ECMO) for severe respiratory failure. Tracings were obtained by means of a Nicolet CA-2000 averager, using a conventional paradigm. The presence or absence of replicated responses at 35 and 75 dB nHL were recorded for each ear. Interpeak latencies I-III, III-V, and I-V were measured and differences between right and left ears were compared, using a matched pair t-test. Wave III-V latencies were longer on the left than right (p less than 0.05), but no significant right-left differences for latencies I-III were noted. Sixteen percent of the infants failed hearing sensitivity criteria, 45% (10/23) had prolonged I-V latencies. At follow-up (age 4 to 12 months) 6/10 infants with prolonged I-V latencies had additional neurologic abnormalities. In this population left ear III-V latencies are prolonged versus right, and the incidence of abnormal BAERs is high. Relative prolongation of left ear III-V latencies (generated from the right brain stem) may be result of right carotid artery and/or jugular vein ligation for ECMO, and abnormal I-V latencies prognosticate future neurologic abnormalities in this population.