A New Animal Model for Hearing Loss and Tinnitus Utilized by Laser Technology

Abstract

Sensorineural hearing loss caused by a shock wave is the most critical etiology relating to blast-induced hearing loss. We have already established small animal models of blast-induced traumatic brain injury and lung injury that are induced by laser-induced shock-waves (LISWs). The use of LISWs has many advantages to mimic traumatic injuries for organs, e.g., highly controllable shock wave energy, site-selectivity and reproducibility. We, herein, present a novel hearing loss model based on LISWs to replicate a blast-induced hearing loss. Our results indicate that threshold elevation of the auditory brainstem response (ABR) after blast exposure was primarily caused by outer hair cell dysfunction induced by stereociliary bundle disruption. The bundle disruption pattern was unique; disturbed stereocilia were mostly observed in the outermost row, whereas those in the inner and middle rows stereocilia remained intact. In addition, The ABR examination showed a reduction in wave I amplitude without elevation of the threshold in the lower energy exposure group. This phenomenon was caused by loss of the synaptic ribbon. This type of hearing dysfunction has recently been described as hidden hearing loss caused by cochlear neuropathy, which is associated with tinnitus or hyperacusis.