老人性難聴

Abstract

Presbyacusis is senescence in the auditory system. Currently, the etiology of presbyacusis is thought to be mainly due to environmental noise and arterial sclerosis. Cumulative effects of social noise influence the auditory function gradually. Sclerotic change of arteries in the brain occurs along the total auditory pathway. Histopathological findings reveal characteristic changes in all parts of the auditory pathway in elderly persons. Alterations include thickening of the ear drum, sclerotic change of the ossicles joint, decreasing number of hair cells, degeneration of the eighth nerve and of the neurons in the auditory center. Pure tone audiograms show gradually progressive sensorineural hearing loss at high frequencies due to lesions characteristic of senescence. During the 30's the threshold at 8 KHz increases a little, but in the 60's the pure tone threshold increases over all frequencies. The maximum speech discrimination parallels the drop in the pure tone threshold level. In contrast to the normal speech discrimination score, the speech discrimination score using frequency distorted words is very low in senile persons. There is no known therapy for presbyacusis. Hearing aids compensate hearing impairment to some extent, but patient's adaptation to hearing aids is undetermined.