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We report a longitudinal follow-up study on six patients with chronic manganese-induced parkinsonism following cessation of manganese exposure. Compared with the 1987 study,their parkinsonian symptoms showed a slow progression,particularly in gait disturbances such as freezing during turning and walking backward with retropulsion.The mean disability scores on the King's College Hospital Rating Scale were 15.0+/-4.2 in 1987 and 28.3+/-6.7 in 1991(p=0.003,paired t test).Review of the video records also confirmed a worsening of parkinsonism,especially in difficulty turning. Three of six patients receiving levodopa treatment had an initial improvement.The response decreased after 2 to 3 years.During the therapy, they did not develop on-off fluctuation or dyskinesia.We conclude that patients with manganese-induced parkinsonism may develop increasing neurologic dysfunction long after cessation of exposure and that their responses to levodopa are different from those of patients with Parkinson' s disease. |
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