Effects on the Hearing of Patients Treated by Irradiation in the Head and Neck Area

Abstract

Ix the treatment by irradiation of malignant tumours in certain areas of the head and neck, the whole auditory apparatus lies within the radiation fields (Figs, i and 2) and may therefore be subject to its full effects. Probably because these effects are not very noticeable, and because no significant damage was observed in the past despite widespread use of irradiation for several other disorders of the ear, little attention has been paid to this subject both by radiologists and otolaryngologists. The literature, in consequence, is very scanty considering the huge amount that has been written about ionization effects in other areas of the body.Desjardins (1931) reviewing thoroughly the earlier animal experiments (Ewald, 1905;Marx, 1909; Chilow, 1927; Thielemann, 1928) which are chiefly related to the ionization effects in the labyrinth, considered the work of those authors inconclusive. He attributed the changes observed in the inner ear to surgical trauma during implantation of capsules containing the radioactive substances and to other mechanical effects of such intervention. Cullen and Girder (1933) were the first to investigate the effects of irradiation on hearing. The dogs they submitted to small doses of X-rays showed an increase in hearing of about 5-5 decibels. This increase would appear after a latent period of about 11 days and last between 2 to 5 weeks after which time hearing would return to initial levels. One animal exposed to a cumulative dose up to IT,100 r. showed no impaired hearing during or after the experiment.Novotny (1951) studying the ionization effects in guinea-pigs found a decrease in the hearing of about 8-4 db. at a frequency of 4,000 c.p.s. There were no changes in the histology of the inner ear and no alteration in the intralabyrinthine pressure.Kozlov (1958) also found a decrease in the hearing of guinea-pigs exposed to irradiation. This impairment was in the range of 3 • 9 to 9 • 1 db., and involved all frequencies between 500 and 8,000 c.p.s.

Ototoxic Effects of Irradiation

“…In Novotny's [7] research hearing impairment of 8.4 dB was noted after 12-72 Gys radiation dose which was more than our study. In Kozlov's [8] study on 10 guinea pigs, 8.9-9.1 dB hearing loss was demonstrated while Dias [9] noted average 9.9 dB deterioration of hearing threshold after 10-180 Gys radiation dosage which was also much more than our study.…”

Radiation-Induced Ototoxicity

“…Edema and fibrosis resulting from RT can interfere with muscle function and lead to eustachian tube dysfunction (Dias 1966). Abnormalities of the mucosa of middle ear affect the production of mucous and its transportation down the eustachian tube (Fischer et al 1978).…”

“…The incidence of post-RT SNHL has been reported to vary from 0 to 54 % in various studies (Dias 1966;Moretti 1976;Anteunis et al 1994;Raaijmakers and Engelen 2002;Kwong et al 1996;Grau et al 1991) Most studies (Kwong et al 1996;Honore et al 2002) that have reported significant hearing loss at high frequencies (4 kHz and above), which may be outside the primary range of human speech (1-3 kHz), are still relevant since normal hearing in young people extends to 20 K; above the age of 50, it is typically limited to 10 kHz. In a review of nine studies, when averaged over all frequencies (0.5, 1, 2, and 4 kHz), the incidence of SNHL was 18 ± 2 %.…”

“…Leach (1965) in a survey of 56 head-and-neck cancer patients subjected to RT, reported that 20 (36 %) of the patients developed a hearing deficit. Dias (1966) reported a series of 29 patients treated with radiation of 1,000-18,000 Roentgen for a variety of head-and-neck tumors, with some patients showing various hearing disturbances and some showing serviceable hearing at a significant time interval after radiation. Moretti (1976) reported audiological data showing SNHL in 13 patients who received radical or postsurgery radiation and suggested that older subjects may be more susceptible to the effects of radiation.…”

Post irradiation hearing loss in head/neck patients in Lagos, Nigeria

“…The documented effects of therapeutic ionizing radiation on the ear varies from relative resistance, to temporary conductive hearing loss(CHL) and permanent sensorineural (SNHL) and [5][6][7] mixed hearing loss(MHL) . The temporary hearing impairment can result from eustachain tubes dysfunction, radiation induced otitis media and transient vasculitis of inner 6 ear vessels .…”