FURTHER-STUDIES USING HIGHER DOSES OF BOTULINUM TOXIN TYPE-F FOR TORTICOLLIS RESISTANT TO BOTULINUM TOXIN TYPE-A

Objective-A previous study of botulinum toxin type F (BTX-F) treatment for torticollis had shown a dose of 520 MU to be effective, but for a much shorter duration than is usual with botulinum toxin type A (BTX- A). The objective was to assess the effect of a higher dose of BTX-F. Methods-Four of the previously treated patients, plus an additional pa tient, were treated with a higher dose of 780 MU BTX-F. All were secon dary nonresponders to BTX-A due to neutralising antibodies. A test inj ection of 40 MU BTX-F was also given into the extensor digitorum brevi s muscle (EDB), to examine the time course of the biological effect of the toxin electrophysiologically. Patients were followed up at two, f our, eight, and 12 weeks. Results-All patients reported subjective imp rovement lasting from seven to 11 (mean 8.6) weeks accompanied by a si gnificant reduction in mean clinical severity scores at two weeks. Fou r patients had pain which was substantially reduced. The electrophysio logical studies confirmed biological sensitivity to the toxin in all p atients, showing a significant change beginning at two weeks and retur ning to baseline at 12 weeks. The time course of this effect parallele d roughly that of the clinical response. The four patients who had pre viously received 520 MU BTX-F reported that the response was better an d longer in duration with 780 MU. Dysphagia was more common than repor ted with the lower dose. Conclusion-Better results are possible with h igher doses of BTX-F but the duration of benefit is still shorter than with BTX-A, seemingly due to a shorter duration of neuromuscular junc tion blockade.