Electrical auditory brain stem responses (EABR) and electrical middle latency responses (EMLR) were recorded from patients who had received the Nucleus multichannel cochlear implant system. Twenty-five sequential patients had either intraoperative or outpatient EABR testing. We also recorded EMLRs from several outpatients. EABR results were consistent among all patients tested. Wave V mean latencies were the shortest (3.82 msec) for the most apical electrode (E20) and increased slightly for the medial (E12) and basal (E5) electrodes (3.94 and 4.20 msec, respectively). Absolute latencies for all EABR component waves were observed to be 1 to 1.5 msec shorter than typical acoustic auditory brain stem response (ABR) mean latencies.
Down's syndrome has been associated with hearing loss and otitis media. Because of difficulty in examination, however, there have been few detailed otologic studies on this population. An understanding of the nature and frequency of ear disease in Down's syndrome is important, since it is common and occurs in more than one in every 600 live births. To define the aural manifestations of Down's syndrome, complete otologic and audiometric examination was performed on 107 consecutive patients. This included micropneumatic otoscopy, pure-tone and speech audiometry, impedance tympanometry, and, in some cases, electronystagmography. Deficient hearing was found in 64% of these patients, and of these hearing losses, 83% were conductive. Surprisingly, middle ear effusion or tympanic membrane perforation accounted for only 60% of the conductive hearing losses. This finding prompted us to examine five temporal bones of children with Down's syndrome. These histologic sections revealed middle ear abnormalities including fixation and superstructure deformity of the stapes and dehiscence of the fallopian canal. Operative findings in 16 procedures on patients with Down's syndrome and conductive hearing loss support those findings.
We have studied the prediction of behavioral threshold and comfort values for 11 patients who use the Nucleus 22-channel cochlear implant by means of the results of electrical auditory brain stem response (EABR) procedures. For prediction purposes, EABR and behavioral testing were done in the same electrode mode configuration for three specific electrodes. The results of this investigation suggest that EABR threshold current level is consistently near the behavioral comfort current level, rather than the patient's behavioral threshold level.
This study assesses several electrocochleographic (ECoG) duration and amplitude measures in a clinically defined Meniere's group and compares the results with those from a normal hearing control group and a hearing loss group (cochlear). The summating potential (SP)/action potential (AP) amplitude ratio was the most efficient diagnostic measure, with 62% of the Meniere's group demonstrating abnormal ratios compared to 4% of the normal control group and 17% of the cochlear group. The SP changes were then studied from three angles: 1. Comparison of SP changes with glycerol test results; 2. Comparison of ECoG results before and after shunt surgery; and 3. Recording of SP's in guinea pig ears in which hydrops had been created by obliterating the endolymphatic duct.
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