Movement Dysfunction as a Neuropathology of Illicit Stimulant Abuse

The widespread and increasing use of illicit stimulants is a global problem. There is evidence that these drugs exert long-term effects on dopaminergic (methamphetamine, cocaine) and serotonergic (ecstasy) systems and therefore have the potential to adversely affect movement. In addition, methamphetamine produces structural changes in the substantia nigra that have been associated with significantly increased risk of Parkinson's disease. Studies of movement in abstinent stimulant users show abnormalities including impaired performance on the grooved pegboard test of hand function, reduced maximal speed of finger movement, and, in abstinent ecstasy users, an increase in tremor during movement. Case studies suggest that clinical manifestations of stimulant-induced movement abnormalities may include chorea, tics, and parkinsonian symptoms. For methamphetamine, there is evidence from epidemiological studies that the risk of Parkinson's disease is increased approximately twofold in former users of the drug. With the future increase in the number of former stimulant users in the population, there is potential for significant increases in the prevalence of movement disorders.