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.

Pre-lingually deaf children can perform as well as post-lingually deaf adults using cochlear implants.

Both pre-lingually deaf children and post-lingually deaf adults benefit from cochlear implants. These adults have a memory for speech sounds, but the children do not. In this preliminary investigation, we asked whether it was possible for these children to obtain high scores similar to the adults. We compared 21 prelingually deaf children to 81 post-lingually deaf adults using multichannel cochlear implants on the same test of sentence recognition. The children were selected to have the vocabulary and language sufficient to complete the test. Scores from the children, ranged from 0 to 97% correct. About one half of the children scored above 70% correct. Scores from the adults ranged from 0 to 100% correct with about one half of the adults scoring over 60%. Many of the children are scoring as well or better than adults are scoring. We conclude that the auditory system of pre-lingually deaf children is sufficient to obtain levels of speech recognition similar to post-lingually deaf adults.

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.