Minimum Electromyographic Burst Duration in Healthy Controls: Implications for Electrodiagnosis in Movement Disorders.

BACKGROUND

Electromyogram (EMG) burst duration can provide additional diagnostic information when investigating hyperkinetic movement disorders, particularly when a functional movement disorder is suspected. It is generally accepted that EMG bursts <50 milliseconds are pathological.

OBJECTIVE

To reassess minimum physiological EMG burst duration.

METHODS

Surface EMG was recorded from face, trunk, and limb muscles in controls (n = 60; ages 19-85). Participants were instructed to generate the briefest possible ballistic movements involving each muscle (40 repetitions) or, in muscles spanning joints, to generate rapid rhythmic alternating movements (20-30 seconds), or both.

RESULTS

We found no effect of age on EMG burst duration. However, EMG burst duration varied significantly between body regions. Rhythmic EMG bursts were shorter than ballistic bursts but only significantly so for lower limbs (P < 0.001). EMG bursts of duration <50 milliseconds were frequently observed, particularly in appendicular muscles.

CONCLUSION

We present normal reference data for minimum EMG burst duration, which may assist clinical interpretation when investigating hyperkinetic movement disorders.