J Korean Assoc EMG Electrodiagn Med Search


J Korean Assoc EMG Electrodiagn Med 1999;1(1):55-60.
Published online January 1, 1999.
EMG Interference Pattern in Upper Motor Neuron and Lower Motor Neuron Weakness
Objectives : Some patients with upper motoneuron (UMN) lesion have varying degree of lower motoneuron (LMN) involvment. This study was undertaken to distinguish UMN and LMN weakness. Methods : The compound muscle action potential (M response) amplitude and interference patterns including mean amplitude(MA), root mean square(RMS) and turns(T) during maximal voluntary contraction were maeasued with surface elextrodes to distinguish UMN and LMN weakness in the 17 patients with peripheral nerve lesion, 20 with central nerve lesion and 20 healthy adults. Abductor digiti quinti, abductor hallucis, biceps brachii and tibialis anterior were examined. Results : The parameters of interference pattern and M amplitude showed significant differences among the muscles in normal controls. In the muscles with weakness due to UMN and LMN lesion M amplitude, MA, RMS and T significantly decreased and MA and RMS correlated positively with muscle strength. The M amplitude more decreased in LMN weaknes than that of UMN. In UMN lesions, the value of M/RMS significantly increased and correlated negatively with muscle strength. In peripheral nerve lesions, RMS/T increased significantly and correlated positively with muscles strength and post injury duration. Conclusions : therefore the analysis of interference patterns could be a useful method to identify peripheral nerve involvement in patients with UMN lesion.
Key Words: Interference pattern, Motoneuron
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