Muscle-fiber conduction velocity and electromyography as diagnostic tools in patients with suspected inflammatory myopathy: a prospective study.
Combinations of different techniques can increase the diagnostic yield from neurophysiological examination of muscle. In 25 patients with suspected inflammatory myopathy, we prospectively performed needle electromyography (EMG) and measured muscle-fiber conduction velocity (MFCV) in a single muscle, using a technique with direct muscle-fiber stimulation and recording. Results of MFCV were compared with final diagnosis, EMG, and needle muscle biopsy. Diagnostic accuracy of combined MFCV and EMG studies was 72%, compared to 60% for EMG alone. This improvement was due to a gain in specificity. The MFCV did not prove useful in discriminating inflammatory myopathy from other myopathies. Furthermore, we found a correlation of 92% between variability of MFCV and myopathic changes in muscle biopsy. We conclude that the utility of electrodiagnostic examination can be increased if EMG examination is combined with MFCV studies.
Blijham
Paul J
PJ
Department of Clinical Neurophysiology, Institute of Neurology, University Medical Centre Nijmegen, PO Box 9101, 6500 HB Nijmegen, The Netherlands.
Hengstman
Gerald J D
GJ
Ter Laak
Henk J
HJ
Van Engelen
Baziel G M
BG
Zwarts
Machiel J
MJ
D000200:Action Potentials / Q000502:physiology*; D000328:Adult; D001707:Biopsy, Needle / Q000592:standards; D004558:Electric Stimulation; D004568:Electrodiagnosis / Q000379:methods; D004576:Electromyography / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018485:Muscle Fibers, Skeletal / Q000473:pathology / Q000502:physiology*; D018482:Muscle, Skeletal / Q000473:pathology / Q000503:physiopathology*; D009220:Myositis / Q000175:diagnosis* / Q000473:pathology / Q000503:physiopathology*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013223:Statistics as Topic