Automatic analysis of the electromyogram in patients with chronic partial denervation.

The technique of automatic analysis of the electromyogram has been applied to patients with chronic partial denervation due to a wide variety of causes. Elevation of the mean amplitude more than 2 SD above the control group mean without significant change in the mean turns count was a consistent index of chronic partial denervation. The degree of elevation was linked to the severity of the weakness in motor neurone disease. Elevation of mean amplitude of comparable degree was found in patients with motor neuropathies of long duration. The elevation of mean amplitude is considered to be due to increase in the density of muscle fibres in the motor units due to reinnervation.