Fascicular twitching of muscles, with or without atrophy, may occur at the level of a lesion in the spinal cord when the corresponding region of the anterior horn or the motor roots are involved.1 Below the level of the lesion hyperactive reflexes and other signs of spasticity are usually present. Both types of signs may be studied by means of electromyography, but an investigation of the fasciculations appears to be of greater localizing value than a study of the abnormal phenomena which result from lesions of the long tracts.
Fascicular twitches are the responses of single motor units to stimuli, arising presumably anywhere along the course of the lower motor neuron.2 They are accompanied by characteristic action potential discharges, which are best seen in records obtained with coaxial needle electrodes.3 In examination of patients with manifest muscular twitches, such as those characteristic of progressive muscular atrophy and