The present pilot study evaluated the effect of
botulinum toxin A on primarily non-dystonic
tremors using accelerometry in a single-blind, placebo-controlled design. Resting, postural, intention, or head
tremor were assessed before and approximately 1 month after intramuscular saline and
botulinum toxin A (25-50 U) respectively. Half of the patients showed > or = 30% placebo effect.
Tremor in 10 of 17 patients (60%) studied improved further after
botulinum toxin A (range 30-95%), exceeding the placebo effect by > or = 30%. Nine patients demonstrated clinically significant focal weakness in the extensor muscles after
botulinum toxin A which interfered with fine movements. Patients were subdivided into PD-like and ET-like
tremor(s). Both groups experienced large placebo effects for
resting tremor, with little or no further improvement after
botulinum toxin A. The improvement in postural
tremor after
botulinum toxin A, of 40% in the PD-like and 57% in the ET-like groups, however, was approximately twice that of placebo. In conclusion,
botulinum toxin A exerts a modest tremorlytic effect, however the dose, and its distribution over the sites injected, need to be optimised to minimise focal weakness.