Single-fiber electromyography for studying the effect of betamethasone on normal neuromuscular junctions in man.

The effects of steroids on normal end-plate in vivo were evaluated in man by using single-fiber electromyography (SFEMG). SFEMG was performed on voluntarily activated extensor digitorium communis muscle under basal conditions and 1 week later an intramuscular injection of 4 mg betamethasone per day was administered for 7 days. Ten patients with low back pain were examined. Steroid therapy did not induce any statistically significant variation either of the mean jitter value or of the percentage of recordings with abnormally high jitter. The results of this study do not give evidence of a direct effect of steroids on normal neuromuscular junction.