[Hemifacial spasm treated with botulinum toxin].

Botulinum toxin produces a transient presynaptic focal block at the neuromuscular junction. Thus it induces muscle weakness which has a significant beneficial effect on hemifacial spasm. Fifty-four patients were treated and received at least 2 and at the most 22 consecutive injections over a 5-year period. Injections were repeated every 9 weeks on average. The interval between injections corresponded to the time elapsed between the last injection and the re-emergence of spasms. Nineteen patients abandoned the treatment for various reasons. The most frequent side-effect was a ptosis which was observed in 1 out of 6 injections. Ptosis is due to diffusion of the botulinum toxin over a territory larger than expected. The results obtained in 42 patients were analyzed: there was no effect in 7 patients (17%); 11 patients improved by less than 50%; 13 by 50 to 70% and 11 more than 75%.