Report on our experience of using contralateral routing of signals for tinnitus retraining therapy

In tinnitus retraining therapy (TRT) for the treatment of tinnitus associated with unilateral hearing loss, sound input into the affected or unaffected ear is provided with the use of a sound generator (SG) or hearing aids. In patients with profound unilateral hearing loss of 90dB or over, the use of hearing aids is considered as being ineffective; therefore, contralateral routing of signals (CROS) has been proposed as a means of providing hearing support. A CROS hearing aid is worn on the affected ear as a transmitter and transmits sounds around the affected ear to a hearing aid in the unaffected ear. A total of 104 patients with tinnitus (62 men and 45 women) visited the Tinnitus and Hearing Loss Clinic of the Shin-Yurigaoka General Hospital during the 1-year period from January 2018 to December 2018. A total of 92 patients (54 men and 38 women) received TRT with a hearing aid. We encountered 2 patients who developed tinnitus after sudden hearing loss, in whom the distress caused by the tinnitus and the hearing loss was alleviated by implementation of TRT with a CROS hearing aid. Both the patients had profound severe hearing loss in the affected ear. One patient received treatment with a CROS hearing aid from the beginning, with improvement. In the other patient, a conventional hearing aid was changed to a CROS hearing aid after the patient showed no improvement with the conventional air conduction hearing aid worn in the affected ear. After the switch to a CROS hearing aid, the patient reported a sense of improvement. We also encountered 1 other patient with profound severe hearing loss who did not use a CROS hearing aid. We evaluated the cases, speculate that? the sounds around the affected ear caught by the CROS in the unaffected ear gave sufficient input of external sounds to both ears, which may have contributed to the alleviation of the patients' tinnitus.