SPECIFITY AND SENSITIVITY OF TRANSIENT CLICK-EVOKED OTOACOUSTIC EMISSIONS (TEOAE) IN CHILDREN

Transient click evoked otoacoustic emissions (TEOAE) have been shown to be a good test of hearing impairment especially when used for infant screening. However, occasional cases of false positive results - TEOAEs in spite of severe hearing loss - have been reported. This study encompasses 243 children whose hearing thresholds were known from subjective hearing tests and - in questionable cases - derived from additional auditory evoked potentials. The TEOAEs proved to have a high sensitivity (93%) and a reasonable specifity (67%), if the margin between good and bad hearing was set at 30 dB. However, four ears showed good TEOAEs in spite of poor hearing thresholds. In three cases, the children proved to have a central auditory hearing loss due to a cerebral disorder. One child with bilaterally superb TEOAEs had a unilateral deafness of unclear origin with no obvious retrocochlear or central disorder. Possible explanations under discussion included the presence of a retrocochlear lesion which was too small to show up in the tests used or that the defect was located just between the outer hair cells and the first neuron, for example in the inner hair cells. Additionally, efferent inhibition might cause a functional deafness as described by Rajan (1989) for the guinea pig. The results also show that TEOAEs should always be used in the differential diagnosis of hearing impairment in generally disabled children. The need for hearing aids and especially their adjustment has to be discussed in case of good TEOAEs, i.e., normal peripheral hearing. The use of a hearing aid without any peak clipping and gain control on the basis of subjective hearing tests and ABR only, as is sometimes suggested, may lead to severe hearing loss in these cases due to the loudness of the hearing aid.