Low-dose botulinum toxin-a treatment of cervical dystonia - a double-blind,randomized pilot study

The purpose of the study was to evaluate the clinical efficacy of low-dose botulinum toxin (BTX) treatment of cervical dystonia in a double-blind, randomized pilot study. Thirty-one patients with cervical dystonia and a minimum of 2 previous Dysport treatments received either a mean total target dose of 547 +/- 113 mouse units (MU) (group A, 500 MU Dysport/ml) or a 4-times-diluted preparation 130 +/- 32 MU (group B, 125 MU Dysport/ml). Assessment was made before and 4 weeks after the injection using Toronto Western Spasmodic Torticollis Rating Scales (TWSTRS). Additionally, a self-response scale evaluated the patients' subjective condition for 12 weeks after injection. TWST rating before and after injection revealed comparable clinical improvement in both groups. The severity of cervical dystonia at study entry had no effects on therapeutic effects of either preparation. Self-rating revealed comparable subjective improvement in both groups; however, 3 patients of group B received reinjections due to insufficient effects of the injection. Our findings suggest that low-dose treatment of cervical dystonia with Dysport may be clinically effective during maintenance therapy, at least for a limited period of time. Long-lasting effects of previous Dysport treatments at conventional doses and possibly improved diffusion of a highly diluted toxin preparation may have contributed to the effects of the low-dose regimen. Our data emphasize the need for further studies in order to clearly identify optimal toxin preparations for therapeutic uses of BTX-A in neurologic disorders.