Effects of Dopamine on Motor Recovery and Training in Adults and Children With Nonprogressive Neurological Injuries: A Systematic Review

Background. The strong link between dopamine and motor learning has been well-established in the animal literature with similar findings reported in healthy adults and the elderly. Objective. We aimed to conduct the first, to our knowledge, systematic review of the literature on the evidence for the effects of dopaminergic medications or genetic variations in dopamine transmission on motor recovery or learning after a nonprogressive neurological injury. Methods. A PubMed search was conducted up until April 2018 for all English articles including participants with nonprogressive neurological injury such as cerebral palsy, stroke, spinal cord injury, and traumatic brain injury; quantitative motor outcomes; and assessments of the dopaminergic system or medications. Results. The search yielded 237 articles, from which we identified 26 articles meeting all inclusion/exclusion criteria. The vast majority of articles were related to the use of levodopa poststroke; however, several studies assessed the effects of different medications and/or were on individuals with traumatic brain injury, spinal cord injury or cerebral palsy. Conclusions. The evidence suggests that a brain injury can decrease dopamine transmission and that levodopa may have a positive effect on motor outcomes poststroke, although evidence is not conclusive or consistent. Individual variations in genes related to dopamine transmission may also influence the response to motor skill training during neurorehabilitation and the extent to which dopaminergic medications or interventions can augment that response. More rigorous safety and efficacy studies of levodopa and dopaminergic medications in stroke and particularly other neurological injuries including genetic analyses are warranted.