Evaluation of Hearing Loss in 5 Cases of Mitochondrial Encephalomyopathy.

Mitochondrial encephalomyopathies are clinically heterogeneous disorders that can affect multiple systems besides skeletal muscle and/or CNS and are usually defined by morphological abnormalities of muscle mitochondria. There are several distinctive syndromes, such as the Kearns-Sayre syndrome; myoclonus epilepsy with ragged red fibers (MERRF); and mitochondrial myopathy, encephalopathy, lactic acidosis and strokelike episodes (MELAS).Auditory function was evaluated in 5 patients with mitochondrial encephalomyopathies including one case of the Kearns-Sayre syndrome, 3 cases of MELAS, and one case of unclassified form of the disorders. Sensorineural hearing loss was observed in four of 5 cases but other neurotological disorders such as vestibular dysfunction were not detected in any of these patients.Although hearing impairment has been reported in patients with Kearns-Sayre syndrome, there have been few reports on the detailed audiometric testing results of MELAS or MERRF. Our audiometric examination revealed that the hearing loss in patients with MELAS was sensorineural in nature and that deterioration of hearing was considerably progressive with the passage of time. However, the precise site of the lesion in the auditory system could not be confirmed because diagnostic audiometric test batteries were not always applicable to these patients since they often became progressively demented or totally deaf during the course of their illness.