Late effects of radiotherapy on hearing

Summary The effect of radiotherapy on hearing was studied in 30 patients who were treated by surgery and radiotherapy for a parotid neoplasm. Functions of the irradiated ear were compared with those of the non-irradiated ear in the same patient. Tympanometry showed a small but significant reduction of static compliance on the irradiated side when compared with the non-irradiated side. Audiometry showed a significant increase in hearing loss in the 1–2, 4–8 and 10–20 kHz ranges that increased with frequency. This hearing loss was mainly sensorineural in contrast to hearing loss at 250–500 Hz, where it was more of a conductive type. There appeared to be a significant dose-effect relation in sound perception at 4–8 kHz. Doses to the cochlea of less than 55 Gy seldom caused a hearing loss, in contrast to doses exceeding 65 Gy. Overall, radiotherapy was found to cause significant, mainly sensorineural hearing losses, which were partly dose-dependent.