The hyperkinetic abnormal movements scale: a tool for measuring levodopa-induced abnormal movements in squirrel monkeys.

The Hyperkinetic Abnormal Movements Scale (HAMS) was developed based on extensive observation of normal and abnormal movements in squirrel monkeys. The observations of abnormal movements were performed using animals that had undergone prior lesioning with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) that subsequently developed levodopa-induced abnormal movements. Specific and easily observable changes in behavior were used to delineate the boundaries between each rating level of the scale. The full spectrum of abnormal behavior at each rating level was then characterized for the squirrel monkey. Once the scale was fully developed and finalized, reliability testing revealed strong inter-rater (r = 0.959) and intrarater reliability (r = 0.930 to 0.941). Novice raters were easily taught its use and subsequently could use the scale with strong inter-rater reliability (R = 0.9057). In further studies of levodopa-induced abnormal movements, the HAMS was demonstrated to be highly sensitive, highly specific, and valid, both internally and when compared with an objective measure of abnormal movements. Although the scale was developed in MPTP-lesioned squirrel monkeys treated with levodopa, it might provide a framework for the standardized measurement of hyperkinetic abnormal movements in other primates and other experimental conditions.