Clinical and Brain MR Imaging Features Focusing on the Brain Stem and Cerebellum in Patients with Myoclonic Epilepsy with Ragged-Red Fibers due to Mitochondrial A8344G Mutation S. Ito

SUMMARY: We report 3 patients with myoclonic epilepsy with ragged-red fibers (MERRF) diagnosed by mitochondrial A8344G mutation. Cerebellar ataxia was the first symptom in all patients. Conven-tional brain MR imaging showed atrophy of the superior cerebellar peduncles and the cerebellum in all patients and brain stem atrophy in 2 patients. In diffusion tensor analysis, fractional anisotropy of the superior cerebellar peduncles was mildly decreased in 1 patient. There was a discrepancy between clinical disabilities (severe) and radiologic abnormalities (mild). This discrepancy and atrophy of the superior cerebellar peduncles and the cerebellum may be important findings suggesting a diagnosis of MERRF. Myoclonic epilepsy with ragged-red fibers (MERRF) is arare mitochondrial disorder featuring myoclonus, sei-zures, mental deterioration, cerebellar ataxia, hearing loss, muscular weakness, and other clinical symptoms. The A8344G or A3243G mutations of mitochondrial deoxyribo-nucleic acid (DNA) are the genetic causative factors.1-3 The clinical phenotype and prognosis are better for patients with the A8344G mutation than for those with the A3243G muta