Interim assessment of candidates for cochlear implants

Audiologic and radiographic response of NF2-related vestibular schwannoma to erlotinib therapy

BACKGROUND

A 48-year-old man presented to a neurologist with complaints of bilateral hearing loss and tinnitus. The patient was a member of a large family affected by neurofibromatosis type 2 and first noted hearing loss 10 years before presentation.

INVESTIGATIONS

Medical and neurological examination, MRI scan of the brain and spinal cord, pure-tone audiometry, NU-6 monosyllabic word test with phoneme scoring, City University of New York topic-related sentences test, noise/voice test of minimal auditory capability battery.

DIAGNOSIS

Progressive neurofibromatosis-type-2-related vestibular schwannomas.

MANAGEMENT

Annual cranial MRI and audiology, surgical resection of right vestibular schwannoma, high-power behind-the-ear hearing aid, erlotinib therapy for progressive left vestibular schwannoma.

Considerations of cochlear implant surgery

Although cochlear implants have been reported to be easy to perform, some difficulties have been experienced in 4 of 21 operations. In order to make this surgery easier, the following points should be considered. Pre-operative CT and MRI must be performed in order to determine the condition of the cochlea. To determine the condition of the round window, exploratory tympanotomy is recommended in some cases. After insertion of the electrode in the cochlea, a radiograph should be taken during the operation to confirm that the electrode is correctly positioned.

Audiological Management and Performance of Adult Cochlear-Implant Patients

We review the signal-processing strategies of three of the most common cochlear implants in use today, the single-channel House, the multichannel Nucleus, and the Ineraid devices. The results of 65 postlinguistically-deafened patients tested at The University of Iowa are reviewed. The tests include everyday sound, accent, word and sentence recognition, as well as noise/voice differentiation. For all tests, patients with the Nucleus and Ineraid cochlear implants outperformed those with the House implant. In general, selection criteria should focus on comparing the performance of Patients who have already received an implant. Prelinguistically-deafened adults are typically not good cochlear-impact candidates. Cochlear-implant teams should be aware of the enormous time commitment for testing and rehabilitation of these patients, and be prepared to handle frequent implant breakdowns. Nevertheless, cochlear-implant patients have been helped significantly be these devices.

Perception of connected speech without lipreading, using a multi-channel hearing prosthesis

Four of 13 totally deaf patients implanted with the Nucleus multi-channel hearing prosthesis at the University of Melbourne have demonstrated the ability to understand connected speech without lipreading or other visual cues. These patients were able to repeat verbatim unknown material read by a tester at rates of up to 35 words per minute. They were also able to understand an average of 78% of key words in everyday sentences in ideal acoustic conditions and 51% of equivalent material over the telephone. These results show that with a good proportion of postlingually deaf patients, the multi-channel hearing prosthesis can not only act as an aid to lipreading, but also restore effective speech understanding without lipreading.

The UCH/RNID cochlear implant programme: patient selection

After an initial postal questionnaire, patients undergo a series of tests and assessments designed to establish their suitability for implantation. The following criteria should be met: Total or profound post-lingual hearing loss. Sufficient age to give informed consent. General good health. Psychological stability. Unable to benefit from hearing aids. Free from middle ear or mastoid disease. Detailed medical, audiometric, vestibular and psychological investigations are performed, as well as acute electrical stimulation of the cochlea, and a hearing aid trial in those subjects with some measurable hearing. Fifty-two applicants have so far been assessed and of these 14 have been found to be suitable for implantation and seven have received implants.

Comparison of different speech processing strategies on patients receiving the same implant

Two subjects with transcutaneously connected 8-electrode scala tympani implants were given subsets of the Minimal Auditory Capabilities test during stimulation with five speech processing strategies--two single channel and three multichannel. While there were significant (p = 0.05%) scores on some items with all types of stimulation, one subject did as well with single channel analog as with multichannel stimulation. She is an enthusiastic full-time user of single channel stimulation. The other, a nonuser of the same device, preferred (and performed better with) one of multichannel stimulation. This is an interim report because neither subject has yet had the opportunity of nonlaboratory use of the multichannel schemes.

Results of a Preliminary Clinical Trial on a Multiple Channel Cochlear Prosthesis

Speech discrimination testing was carried out under clinical trial conditions for eight profoundly postlingually deaf adults to assess the efficacy of a newly developed 22-channel cochlear prosthesis and speech processor. Three months postoperatively, these patients showed significantly better results with the cochlear prosthesis than for preoperative testing with a conventional hearing aid or vibrotactile aid (following a 6-month trial with the aid) on each of a series of tests from the Minimal Auditory Capabilities battery. Assessment of lipreading enhancement using standard speech tests, consonant recognition studies, and speech tracking showed significant improvements for each patient when using the cochlear prosthesis. Six patients showed a significant amount of open set speech discrimination without lipreading at levels which have not been reported for single electrode cochlear prostheses. The two patients who performed poorly on these tests both had restricted multiple channel systems due to their disease, one patient being restricted to virtually a single channel system and the other to only ten of the 22 electrodes. These results indicate that this multiple channel cochlear prosthesis has potential as a treatment for profound postlingual deafness over a wide range of etiologies and ages.

Telephone use by a multi-channel cochlear implant patient. An evaluation using open-set CID sentences

A totally deaf person with a multiple-channel cochlear prosthesis obtained open-set speech discrimination using the telephone. CID Everyday Sentences were presented by telephone to the patient, who repeated an average of 21 per cent of key words correctly on the first presentation, and 47 per cent when a repeat of the sentences was permitted. This result is consistent with the patient's reports of telephone usage.

Audiological results with two single channel cochlear implants

We tested six patients with single channel cochlear implants on several tests from the Minimal Auditory Capabilities battery and the Iowa Cochlear Implant Tests. All patients were able to discriminate some everyday sounds and to identify the number of syllables in the words presented. Five patients were able to identify speaker sex reliably. Surprisingly, some patients had difficulty discriminating between a modulated noise and a voice or between a question and a statement or identifying the accented word in a sentence. On several audiovisual tests, an improvement was observed for the sound plus vision condition compared to the vision only condition. This was particularly true for sentence tests, but was not uniform across patients or across tests.