Levorotatory 5-hydroxytryptophan (10 mg/kg/day) was found to benefit patients with various inherited or acquired cerebellar ataxias in a long-term randomized, double-blind study at the Hopital Neurologique, Alexis Carrel Faculty of Medicine, Lyon, France. Of 30 patients in test and placebo groups, 2 had Friedreich’s ataxia, 8 had postsurgical ataxia, 6 multiple sclerosis, 2 brain stem infarction, and 12 cerebellar cortical atrophy. The majority were adults, and the degree of ataxia was measured by four semiquantitative subtests. The treatment continued initially for four months, was extended in five patients without controls for a further eight months. Levo-5-hydroxytryptophan significantly improved the ataxia score and modified the time of standing upright, the speed of walking, speaking, and writing. The process appears to be serotonin-dependent and provides benefit particularly in static cerebellar disturbances and speech dysarthria caused by lesions of the anterior vermis. 
COMMENT. The rationale for this treatment was the discovery of serotoninergic nerve terminals in the cortex of the cerebellum, and the induction of cerebellar tremor by the experimental depletion of serotonin. The treatment was well tolerated and should be considered for trial in children with Friedreich’s ataxia and in static, postsurgical or post-viral cerebellar syndromes.