[Regression of human cerebellar ataxia under long term administration of 5-hydroxytryptophan]

18 patients with degenerative cerebellar ataxia were given for 12 months, high doses of D-L-5 Hydroxytryptophan (16 mg/kg/day) with a peripheral inhibitor of 5-HTP Decarboxylase. The ataxia was regularly evaluated with a semi-quantitative score and quantitative measurements, allowing a computerized processing of the data. A highly significant improvement of the static ataxia was observed at the 12th month, while adiadocokinesia, hypermetria and dysarthria were also influenced. These results could correspond to the presence of serotoninergic nerve terminals in the cerebellar cortex, the cerebellar deep nuclei and the inferior olivary complex. Moreover, the improvement of the ataxia continued for 3 months after treatment stopped, suggesting an effect distinct from the classical neuromediation phenomenon.