Phenotypic comparison between combined dystonia-parkinsonism and idiopathic adult-onset dystonia

The clinical characteristics of dystonia occurring in association with sporadic neurodegenerative parkinsonism have not been systematically explored or compared with those of idiopathic adult-onset dystonia. This study aims to compare demographic and clinical features, including the distribution of dystonia at onset, dystonia-associated features, and the propensity for spread between patients with combined dystonia-parkinsonism and those with idiopathic adult-onset dystonia. Patients were selected from the Italian Dystonia Registry. The study cohort included 130 patients with combined dystonia-parkinsonism and 355 age- and sex-matched patients with isolated adult-onset idiopathic dystonia. The comparison between combined dystonia-parkinsonism and idiopathic dystonia revealed differences in the distribution of dystonia across body regions, with non-task-specific upper limb dystonia, lower limb dystonia, and trunk dystonia occurring more frequently in patients with combined dystonia-parkinsonism. Additionally, this group exhibited a lower frequency of head tremor, eye symptoms associated with blepharospasm, and sensory tricks, alongside a comparable frequency of neck pain related to cervical dystonia and a family history of dystonia or tremor. The clinical presentation of dystonia differs between combined dystonia-parkinsonism and idiopathic dystonia, especially in terms of the body regions affected. These differences underscore the necessity for additional research and suggest underlying pathophysiological disparities between etiological categories that could significantly influence future diagnostics and therapeutic approaches.