Are There Cochlear Dead Regions Involved in Hearing Loss after Cisplatin Ototoxicity?

Background: The most common complaint of patients affected by chemotherapy-induced hearing loss is difficulty understanding speech in noisy environments despite the use of hearing aids. Cochlear dead regions, those areas with damaged or absent inner hair cells and dendrites, may account for this type of hearing loss. However, it is unknown whether this condition is associated with cisplatin agents. Objective: The aim of this study was to determine whether cisplatin is associated with hearing loss and cochlear dead regions. Methods: This prospective cross-sectional study was conducted in patients participating in routine audiological monitoring during and after chemotherapy treatment. Adults undergoing audiological evaluation who had completed chemotherapy treatment were invited to participate. Patients were divided into 3 groups according to pure tone thresholds. Group 1 patients had thresholds over 70 dB (HL) at 2,000 Hz and higher frequencies. Group 2 patients had thresholds below 70 dB (HL) up to 2,000 Hz. Patients in the control group had normal thresholds at all frequencies. The threshold equalizing noise test (TEN[HL]) was used to identify cochlear dead regions by repeating thresholds in the presence of TEN noise played from a compact disc. The presence of cochlear dead regions was established when the masked threshold was 10 dB or greater above the TEN level and 10 dB or greater above the absolute threshold at any frequency. Results: Twelve patients were included in study group 1, 10 patients in study group 2, and 7 patients in the control group. Cochlear dead regions were present in all patients with hearing loss and in none of the control group. For groups 1 and 2, mean differences between absolute and masked thresholds were 21 and 16 dB at 500 Hz; 22 and 15 dB at 1,000 Hz; 31 and 17 dB at 2,000 Hz; 32 and 20 dB at 3,000 Hz; and 31 and 21 dB at 4,000 Hz, respectively. Nevertheless, analysis of variance testing with Bonferroni analysis showed a difference between groups 1 and 2 only at 2,000, 3,000, and 4,000 Hz. Conclusion: We found unresponsive or dead cochlear regions in patients who had undergone cisplatin chemotherapy even among patients with mild to moderate hearing loss.