The Effect of Fractionated Radiotherapy in Sensorineural Hearing Loss: An Animal Model

Objectives/HypothesisThe purpose of this study is to assess the effect of fractionated radiotherapy on sensorineural hearing loss using an animal model. Study DesignIn vivo animal study. MethodsEars of 25 guinea pigs were divided into three groups: control, irradiated with a total of 48 gray (Gy), and 71 Gy. Unilateral exposure of 48 Gy and 71 Gy fractionated irradiation was given for a 4-week period. Auditory brainstem response and distortion products otoacoustic emissions (DPOAE) were tested prior to irradiation and 1, 6, 10, and 16 weeks after completion of radiotherapy to assess the hearing threshold shift postradiotherapy over time. ResultsNo significant differences in hearing thresholds between the low dose radiation (48 Gy) and the control group (no radiation) underlined that 48 Gy caused no hearing deficits (P=0.37). The higher dose (71 Gy) showed progressive deterioration of the hearing function over time. Three-way ANOVA interactions revealed significant group-time effects (F= 9.261; P<0.0001). DPOAE analysis demonstrated hearing loss at 71 Gy without progression or recovery at all time points, predominantly in the higher frequencies tested. ConclusionThe present study suggests that in the presence of sensorineural hearing loss due to high- dose fractionated radiotherapy, there is an initial sensorial component; however, the neural component is responsible for its progressivity.