Longitudinal study of the neuromuscular jitter of the extensor digitorum communis muscle was done in 1993 in 10 patients treated with botulinum toxin A (BTXA) by means of stimulated single fibre electromyography (SF EMG). The examination was done before the administration and twice after the BTXAadministration in order to follow up the effect of such therapy on the neuromuscular transmission in remote muscles.The BTXA administration brought about only a small, transient, subclinical increase of jitter. In 7 out of 10 patients who were treated with BTXA for abnormal movements, the SF EMG examination was repeated after 7 to 8 years. In each patient at least 20 neuromuscular junctions were examined (individual jitter MCD) and the mean individual jitters (mean MCD) was estimated. Also the average value of jitter from all patients was estimated (pooled data). The average value of mean MCD was in 1993 20 µs (15–25 µs, SD 3.1 µs) in years 2000–2001 21 µs (17–26 µs, SD 3.0 µs). The pooled value of individual jitters was in 1993 19,46 µs (SD 8.59 µs), after 7 to 8 years it was 21.01 µs (SD 9.76 µs). Differences are not significant (p=0.59, 0.23 respectively). The study has shown that the small increase of neuromuscular jitter just after the BTXA administration is a transient effect and with long-term administration it has no cumulative effect on the injury of the neuromuscular transmission in remote muscles.

        Key words: botulinum toxin, single fiber electromyography, neuromuscular jitter