Audiologic findings in patients with a point mutation at nucleotide 3,243 of mitochondrial DNA.

A mitochondrial tRNALeu(UUR) mutation at nucleotide 3,243 is known to be found in most patients with MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes) and has also been identified in several families with maternally inherited diabetes mellitus and hearing loss. We report here audiologic features in patients with hearing loss associated with the mutation. Four patients without and five with MELAS were studied. Most of the patients had bilateral progressive sensorineural hearing loss. The most common shape of the audiogram was sloping, while cases in the advanced stages had flat audiograms. Speech discrimination scores were generally poor and did not parallel the degree of hearing loss. The present study suggests that the lesion for hearing loss could include both cochlear and retrocochlear involvement, but does not demonstrate a significant difference in the audiologic findings between patients with and without MELAS.