Prebycusis: physiological or pathological.

A study was made on human temporal bones to elucidate the effects of aging on the auditory system. Ninety-six ears from 68 individuals, varying in age from infancy to 84 years, served as 'normal ears'. None of these cases had clinical or pathological evidence of specific ear diseases. 'Pathological ears' consisted of 89 ears from 58 individuals which exhibited slowly progressive hearing loss, and which had no specific known cause for the loss. Two aging phenomena were found to affect the human ear. The first is physiological, and has been called 'auditory senility'. It involves all the different parts of the auditory mechanism equally, and is responsible for the rise in auditory thresholds for the high frequencies, commonly seen in elderly people. The second phenomenon is pathological, and was termed 'auditory decay'. It involves only the perceptive system of the ear, and results in different types of clinical presentations, according to the morphological layer involved. Therefore, the recognition of two aging phenomena which affect the human ear may explain the reason for the wide variations in auditory acuity associated with old age.