Clinical Evaluation of Evoked Electromyography in Human Masseter Muscles

Abstract

     I investigated the clinical implications of the masseteric evoked electromyography (EMG) method. The masseteric jaw jerk reflex and silent period (SP) were studied using an electrode array. The response varied with location and contraction level of masseter muscles. The latency period for the jaw jerk reflex was the same on both sides. I also investigated the relationship between the masseteric nerve and muscles, using electrical stimulation from the skin at the mandibular notch. I observed the M-wave, which is the so-called distal motor latency (DML). The M-wave peaks propagated from the motor end-plate. Although the muscle fiber conduction velocity (MFCV) decreased with fatigue, the DML did not change over time.
      It is suggested that the evoked EMG, e.g. bilateral jaw jerk reflexes, MFCV and DML, are useful parameters for estimating nerve and muscle conditions.