Electrophysiological findings including single fibre EMG in a family with mitochondrial myopathy.
Nerve conduction studies, conventional and quantitative concentric needle EMG and single fibre ENG were performed on 5 clinically affected and 7 clinically asymptomatic members of a family with a mitochondrial myopathy manifesting as a facioscapulohumeral syndrome. Abnormalities of nerve conduction present in 3 clinically affected cases were attributed to co-existent diabetes mellitus. Quantitative CNEMG showed a reduction of the mean motor unit potential duration and increased incidence of polyphasic potentials in all 5 clinically manifest cases consistent with a primary myopathic disorder. Similar but less marked changes were found in 6 of the clinically asymptomatic individuals revealing the presence of a subclinical myopathy. Abnormalities on SFEMG consisting of increases in fibre density and/or jitter were present in all the clinically affected and in 5 clinically normal cases. These changes indicate local reorganization of the spatial arrangement of muscle fibres of the motor unit and a disturbance of neuromuscular transmission. The CNEMG and SFEMG findings are discussed in relation to the histopathological changes in 4 cases.
D000293:Adolescent; D000328:Adult; D003929:Diabetic Neuropathies / Q000503:physiopathology; D004576:Electromyography; D005071:Evoked Potentials; D005260:Female; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000503:physiopathology; D008875:Middle Aged; D008931:Mitochondria, Muscle / Q000502:physiology*; D009046:Motor Neurons / Q000502:physiology; D009412:Nerve Fibers / Q000502:physiology; D009431:Neural Conduction; D009468:Neuromuscular Diseases / Q000503:physiopathology*; D010543:Peroneal Nerve / Q000503:physiopathology; D014459:Ulnar Nerve / Q000503:physiopathology