Centrally mediated late motor recovery after botulinum toxin injection: Case reports and a review of current evidence

Abstract

Objective: Botulinum neurotoxin is commonly utilized in neurorehabilitation as a treatment for focal spasticity. Clinical experience has yielded observations of late motor recovery after intramuscular injection of botulinum neurotoxin, that are not readily explained by the classical mechanism of action of the neurotoxin in controlling spasticity. These findings have triggered speculation regarding a botulinum neurotoxin mediated effect at the central level after peripheral intervention. Methods: A review of current literature reveals evidence of distant action after peripheral botulinum neurotoxin injection in affected muscles, be it in other muscles, nerves, spinal cord or the cortex. Results: Plausible explanations for a centrally mediated late motor recovery after botulinum neurotoxin injection include: (i) direct action of botulinum neurotoxin at distant sites in the central nervous system, mediated by retrograde transport of the neurotoxin into the spinal cord, and (ii) cortical reorganization due to botulinum neurotoxin-induced decrease in peripheral sensory input at the local injection site. Conclusion: Additional research is required to further elucidate these hypotheses, as well as providing specific dosing specifications, patient selection criteria and the interplay with other therapeutic modalities necessary to promote late motor recovery.