KINEMATICS OF FAST WRIST MOVEMENTS IN MANIC-DEPRESSIVE ILLNESS CHRONICALLY TREATED WITH LITHIUM-CARBONATE

Lithium sails have been shown to impair kinematics of fast voluntary m ovements during acute intoxication. The aim of the present study was t o determine whether lithium carbonate affected the kinematics of fast movements in patients chronically treated and who did not exhibit sign s of neurotoxicity. We analysed fast wrist flexion movements in 6 heal thy subjects, in 5 patients presenting a manic-depressive illness with out treatment, and in 8 patients receiving lithium carbonate for a man ic-depressive disease. The mean duration of treatment was 3.9 +/- 4.1 years, the mean daily dose 837 +/- 341 mg and the mean serum level 0.9 5 +/- 0.15 mEq/l. Although mean movement amplitudes were similar in th e 3 groups, the variability of fast movements was increased in patient s receiving lithium salts. The ratio oi maximum to average velocities (Vm/Vave) was significantly higher in patients treated, and their move ments were temporally asymmetrical, with a ratio of acceleration durat ion divided by deceleration duration being lower than in the 2 other g roups. These kinematic abnormalities show that a chronic treatment wit h lithium salts is associated with an impairment of the cerebellar con trol of fast single-joint movements.