Normal cochlear function in mdx and mdx(Cv3) Duchenne muscular dystrophy mouse models

Objectives/Hypothesis: Sensorineural hearing loss has been found in associa tion with inherited muscular dystrophies in humans and in mouse models. An increased brainstem auditory evoked response threshold has been previously reported in the dystrophin-deficient; mdx mouse model for Duchenne muscular dystrophy, suggesting that full-length dystrophin (Dp427) is involved in h earing. The objective of the present study was to confirm cochlear dysfunct ion with this gene defect and determine whether the shorter carboxyl termin us isoforms of dystrophin are also critical in maintaining normal hearing, Study Design: Case controlled, Animal model, Methods: Auditory brainstem re sponse (ABR) audiometry to pure tones was used to evaluate cochlear functio n. Fourteen mdx, 4 mdx(Cv3), and 13 age-matched control (C57BL/6J and C57BL /10ScSn) male mice were tested at 5 weeks and 11 weeks of age, The ABR thre sholds to tone-burst stimuli at 4, 8, 16, and 32 kHz were obtained for each ear and statistically compared (ANOVA) for potential group differences. Re sults: Both mdx and mdx(Cv3) mice demonstrated normal ABR thresholds when c ompared with controls. Conclusions: Both mdx and mdx(Cv3) mouse models have normal hearing by ABR, The authors' data suggest that dystrophin and its c arboxyl terminus isoforms do not play a critical role in hearing in the mou se. This was unexpected, as previous studies-using the brainstem auditory e voked response method suggested that the mdx mouse has an increased thresho ld for hearing.