PubMed · 5522702
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H Güttich. 1970-06-10. [Ear diseases].. https://pubmed.ncbi.nlm.nih.gov/5522702/
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The finding of an abnormally narrow internal auditory meatus during the assessment of a child for cochlear implantation raises the possibility that the meatus may not contain the normal number of nerves. Even with currently available MRI techniques it may be extremely difficult to decide whether or not to offer cochlear implant in such cases. We present a child of 4 1/2 years, assessed for cochlear implantation. MRI and CT imaging suggested aplasia of one vestibulocochlear nerve and hypoplasia of the other. However, audiological tests showed clear responses to sound in both ears and functional use of sound in her daily life. This child was eventually implanted with encouraging postoperative results.
OBJECTIVES: To investigate the relation between different types of exposure to noise and a classic sign of noise induced hearing loss (NIHL), the audiometric notch. METHODS: The study sample had exposure to both continuous and impulse noise and was drawn from a population of electrical transmission workers. Audiograms, taken as part of a hearing conservation programme, were read by three clinicians experienced in the assessment of NIHL. Working independently and using their clinical judgment, they were asked to identify localised increases in the threshold of hearing (audiometric notches) which they would attribute to noise, had a suitable history of exposure been elicited. Prevalent cases of NIHL were identified by the presence of a notch in either ear. Risk factors for NIHL were assessed by a questionnaire which sought information about exposure to air blast circuit breaker noise; firearms; explosions, and continuous noise. The odds of exposure to these factors in those with and without hearing loss were calculated, and odds ratios (ORs) and 95% confidence intervals (95% CIs) were estimated by logistic regression. RESULTS: Of the 648 questionnaires sent out 357 were returned, a response rate of 55%. Of these, at least two out of the three assessors identified 175 (49%) people with a notch at any audiometric frequency. There was no association between these cases and the NIHL risk factors identified by the questionnaire, but a further frequency specific analysis showed a small proportion of people (15 (4%)) with notches at 4 kHz who had the expected associations with exposure to noise and a significant OR for firearms of 4.25 (95% CI 1.28 to 14.1). The much larger proportion of people with 6 kHz notches (110 (31%)) did not show these associations. CONCLUSIONS: To diagnose NIHL it is important to elicit a detailed and accurate history of exposure to noise: although the notch at 4 kHz is a well established clinical sign and may be valuable in confirming the diagnosis, the 6 kHz notch is variable and of limited importance.