The clinical use of multichannel surface electromyography.

Surface EMG motor unit action potentials (MUAPs), recorded with "array" or "matrix" types of electrodes, can be seen to propagate from the motor end plates in both directions along the muscle fibers. We attempted to obtain diagnostic information in muscle disease by using the multichannel surface EMG. The subjects examined were 28 normal controls (5-40 years old), seven patients with myopathy and three patients with neuropathy. The tibialis anterior and the biceps brachii muscles were investigated at weak and moderate contraction levels. In normal muscles, the mean muscle fiber conduction velocity increased with muscle force. In four of seven cases with myopathy, the conduction velocities were reduced compared to normal subjects (p less than 0.01), and there was little or no correlation between the conduction velocity and muscle force. In Duchenne muscular dystrophy, abnormal propagation patterns of MUAPs were obtained. The conduction velocities were within the normal range in the muscles of patients with neuropathy. However, abnormal MUAPs, giant and fasciculation potentials, and diminished discharge patterns of motor units (MUs) were detected during voluntary contraction and at rest in neuropathy.