[Detection of inactivity of the auditory system in the beginning stage with the Freiburg masked speech test]

Late-onset auditory deprivation or "inactivity" phenomenon has been reported in single cases only because it has not been possible to assemble a larger number of calculable cohorts for which all necessary details concerning individual histories are available. Subjects should not be older than 60 years of age and should have had asymmetric hearing for at least about 10 years or should have been wearers of monaurally fitted hearing aids. The development of late-onset auditory deprivation is presented in 6 single cases. All were assessed by the Freiburg speech discrimination test and the distorted Freiburg speech test, with the latter showing greater sensitivity and variability. It is of special interest that the quotient of distorted speech is reduced in subjects who have normal hearing in one ear and considerable hearing loss in the other ear (for example, in the case of unilateral microtia). This effect may be evidence for significant activation of hearing selectivity developing in the brainstem versus inactivation.