Dystonia in Parkinson's disease: clinical and pharmacological features.

We studied the features of dystonia in 9 patients with untreated idiopathic Parkinson's disease and in 56 patients on sustained treatment with L-dopa. Dystonia was seen as an initial symptom in patients with both early- and late-onset Parkinson's disease and included action dystonia of the limbs and cranial dystonia. Although the coexistence of parkinsonism and dystonia suggests a common pathophysiology, antiparkinsonian drugs did not consistently influence dystonic spasms. L-dopa-induced dystonia was seen as an off-period, biphasic, or peak-dose phenomenon. Each type showed a distinctive pattern of localization of dystonic spasms, possibly reflecting neurochemical aspects of basal ganglia somatotopy. Neuropharmacological studies performed in 12 patients suggest that off-period dystonia is genuinely induced by L-dopa and best relieved by antiparkinsonian agents.