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Concentric-needle versus macro EMG. II. Detection of neuromuscular disorders
J Finsterer1, A Fuglsang-Frederiksen
1Ludwig Boltzmann Institute for Research in Epilepsy and Neuromuscular Disorders, Vienna, Austria. fij@2nr.nkr.magwien.gv.at
Objective:
Little is known about the relation and sensitivity of macro-EMG (MA-EMG) compared with concentric-needle EMG (CN-EMG) in the detection of neuromuscular disorders.
Methods:
CN-EMGs and MA-EMGs were recorded from the right brachial biceps muscle of 40 healthy subjects, aged 17-83 years, 20 patients with neurogenic disorders, aged 25-75 years, and 20 patients with myopathy, aged 18-76 years. Motor unit action potentials (MUAPs) were examined.
Results:
In patients with neurogenic disorders CN-MUAP duration, CN-MUAP amplitude, percent polyphasia, MA-MUAP amplitude, MA-MUAP area and fibre density were significantly increased. In patients with myopathy, only fibre density was significantly increased. In patients with neurogenic disorders, the sensitivity of CN-EMG was 80%, and that of MA-EMG 85%. In myopathies, the sensitivity was 50% for each technique. Pooling the results of both EMG techniques, the sensitivity increased to 90% in patients with neurogenic disorders, and to 65% in myogenic disease.
Conclusions:
MA-EMG has a similar sensitivity in the detection of neuromuscular disorders as CN-EMG. Particularly when myopathy is suspected, both techniques should be applied if one is unrevealing.