Objective: To determine the dosing, response expectation, efficacy, and most rational strategy for using intramuscular injections of botulinum toxin A (BTX) for limb disorders.
Design: Open-label prospective analysis of outcome after BTX treatment in patients with limb disorders.
Procedure: Botulinum toxin A prepared from lyophilized botulinum toxin was injected into selected upper and lower limb muscles under electromyographic guidance. Booster injections were given every 10 to 14 days during the first month (if needed) until optimal effects were achieved. Clinical data and muscle strength testing were obtained before the first injections and repeated at each visit. Level of disability, global functional improvement, and relief of pain were evaluated 6 to 8 weeks after the first set of injections. Practical and meaningful BTX doses by muscle, limb, or condition according to specified levels of efficacy were developed.
Main outcome measures: Botulinum toxin A efficacy was calculated as an arithmetic combination of changes in the 3 clinical ratings before and after administration of BTX.
Results: Botulinum toxin A injections were given to 187 patients with limb disorders during an 8-year period (136 with dystonia, 37 with parkinsonian, essential, and cerebellar tremors, and 14 with spasticity). Four overall outcomes from no effect to almost complete improvement in the use of the limb or relief of pain were found, and determined the strategy for follow-up injections. Average BTX efficacy for all patients was 65% and ranged from 83.5% for focal hand dystonia to 35.7% for parkinsonian tremor. Botulinum toxin A injections relieved pain, independent of motor function, in 82.7% of patients with painful muscle spasms.
Conclusions: Botulinum toxin A was found to be a safe and useful treatment of various limb conditions. Botulinum toxin A was significantly more effective when only a few muscles needing low doses were injected, and tended to be more useful in dystonia and spasticity than tremor. Candidates for BTX injection could be categorized functionally into 3 groups independent of the underlying disorders. The only significant adverse effect of BTX injection in limbs was transient weakness in injected or neighboring muscles.