Transcranial Photobiomodulation Therapy in Central and Peripheral Disorders of Tinnitus

Abstract

Abstract Tinnitus is a common annoying symptom without effective accepted treatment. In this study, photobiomodulation therapy (PBMT), which has modulating and restorative effects, was used in the treatment of peripheral and central tinnitus defects in the rat animal model. The laser parameters included a wavelength of 808 nanometer, a power density of 165 milli-watts/cm2, and an energy density of 99 Joules/cm2. Tinnitus was induced by sodium salicylate (SS) injection and confirmed by behavioral test. In tinnitus rats, although the hearing status remained normal in the behavioral test, the auditory brainstem response (ABR) test threshold was increased, indicating the occurrence of hidden hearing loss. In the tinnitus group, there was also a significant increase in the expression of doublecortin (DCX), which is a marker of neural plasticity, in the dorsal cochlear nucleus (DCN), dentate gyrus (DG) of hippocampus and parafloccular lobe (PFL) of the cerebellum. In the treatment group, a significant improvement in the behavioral test and ABR threshold and a significant reduction of DCX expression in the DG were observed. Based on our findings, PBMT has the potential to treat SS-induced tinnitus and hidden hearing loss in rat animal model.