[Facioscapulohumeral muscular dystrophy (FSH) and hearing loss]

It has been reported that cochlea is the lesion of hearing loss in FSH. However, the details of this lesion are not yet sufficiently known. We performed detailed audiologic studies to examine hearing loss in FSH. We experienced 2 cases of FSH associated with hearing loss. Case 1 was a girl aged 5 years, and case 2 a boy aged 15 years. Clinical findings, EMG and muscle biopsy gave a diagnosis of FSH in both cases. Hearing loss was evaluated by pure tone audiography, speech audiography, tympanometry, stapedial reflex, auditory brain stem response and electrocochleography. In case 1, pure tone audiograms revealed high tone hearing loss without an A-B gap. On speech audiography, the maximum articulation score was 100% and proved normal. The tympanogram was type A. Stapedial reflex was normal bilaterally. The threshold of the 5th wave increased markedly on auditory brain stem response. On electrocochleography, the H-curve of the input-output function curves of action potential was recorded, but the L-curve was absent. There were no complaints of hearing loss in case 2, but pure tone audiograms revealed high-tone hearing loss without an A-B gap. The tympanogram was type A. Stapedial reflex was normal bilaterally. On auditory brain stem response, threshold was increased and latency was prolonged when intensity was lowered. The electrocochleograms were almost normal. It has been reported that, in electrocochleography, the L-curve represents the function of the outer hair cells and the H-curve that of the inner hair cells. The electrocochleograms in case 1 showed damage to the outer hair cells.(ABSTRACT TRUNCATED AT 250 WORDS)