Valproate induced parkinsonism

Among side effects due to sodium valproate (VPA) administration, parkinsonism is very rare. We report here three cases of VPA induced parkinsonism. Case 1 (75 year-old-woman) developed parkinsonism (rigidity, akinesia, postural instability) 41 month after the VPA administration (800 mg/day). Parkinsonism resolved within 6 months of discontinuing VPA. Case 2 (70 year-old-man) developed parkinsonism (rigidity, akinesia, postural instability, frozen gait) 15 months after the VPA administration (800 mg/day). Parkinsonism resolved within 6 months of discontinuing VPA. Case 3 (74 year-old-woman) developed parkinsonian gait 7 months after VPA administration (800 mg/ day). Parkinsonian gait resolved within a month of reducing VPA. Pathophysiologic mechanisms of this rare toxic reaction remain unknown. VPA induced parkinsonism is not so rare and has been under-reported and under-recognized. When we are confronted with the patients who develop parkinsonism after VPA administration, the possibility of VPA induced parkinsonism should be considered in the differential diagnosis. Old age, long duration of treatment, and VPA dose maintaining serum therapeutic levels might be predisposing factors for this syndrome.