Auditory neuropathy in mice and humans with Friedreich ataxia

ABSTRACT Objective Recent studies have found that human Friedreich ataxia patients have dysfunction of transmission in the auditory neural pathways. Here, we characterize hearing deficits in a mouse model of Friedreich ataxia and compare these to a clinical population. Methods Sixteen mice with a C57BL/6 background were evaluated. Eight were YG8Pook/J animals (Friedreich ataxia phenotype) and eight wild‐type mice served as controls. Auditory function was assessed between ages 6 and 12 months using otoacoustic emissions and auditory steady‐state responses. At study end, motor deficit was assessed using Rotorod testing and inner ear tissue was examined. Thirty‐seven individuals with Friedreich ataxia underwent auditory steady‐state evoked potential assessment and response amplitudes were compared with functional hearing ability (speech perception‐in‐noise) and disease status was measured by the Friedreich Ataxia Rating Scale. Results The YG8Pook/J mice showed anatomic and functional abnormality. While otoacoustic emission responses from the cochlear hair cells were mildly affected, auditory steady‐state responses showed exaggerated amplitude reductions as the animals aged with Friedreich ataxia mice showing a 50–60% decrease compared to controls who showed only a 20–25% reduction (F(2,94) = 17.90, p