Objective: The aim of this study was to investigate audiologic features and the lesion site of sensorineural deafness with mitochondrial DNA mutation at position 3243.
Study design: Case review.
Setting: The study was conducted at the Kochi Medical School.
Patients: A case of sensorineural deafness in a patient who had a mitochondrial DNA mutation was presented. The incidence of deafness and diabetes mellitus (DM) was very high in the patient's family, but she did not have DM.
Main outcome measures: The patient's mitochondrial DNA was examined. Furthermore, the pure-tone audiogram, the Bekesy audiogram, an auditory brain stem response, and the electrocochleogram were analyzed.
Results: The patient's mitochondrial DNA had a point mutation at codon 3243 (A-->G). The pure-tone audiogram showed moderate sensorineural deafness. An auditory brain stem response showed normal latencies. The electrocochleogram showed an enhanced negative summating potential.
Conclusions: It was speculated that the lesion site of the auditory system was the inner ear. The possible sites in the inner ear were hair cells, the stria vascularis, and the endolymphatic sac.