Afterdischarge activity in neuropathic patients with frequent muscle cramps

Objectives - To evaluate the presence of the afterdischarge activity follow ing M- and F-waves in patients with peripheral neuropathies with or without muscle cramps. Material and methods - Ten patients with peripheral neuropa thies complaining of frequent muscle leg cramps (Group I) and 14 patients w ith peripheral neuropathies without muscle cramps (Group 2) participated in our study. The afterdischarge was evaluated through a repetitive stimulati on of the peroneal and tibial nerves. Results - An abnormal afterdischarge activity following F-wave was identified below 5 Hz only in Group 1. On hig h frequency of stimulation (>5 Hz), this activity was present in every pati ent in Group 1. Moreover, it was particularly present in the muscle affecte d by cramps. Conclusion - Since the afterdischarges following F-waves have been considered to be the result of a hyperactive "bistable" state of alfa- motor neurons, our findings are indicative of an impairment of motor neuron excitability. Thus, it is hypothesizable that either peripheral and centra l mechanisms may together contribute in producing muscle cramps.