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Essential tremor (ET) is a common clinical syndrome characterized by action tremors affecting both upper limbs that can compromise manual tasks' execution and impair functional and social performance. The primary pharmacological treatment is symptomatic, but effective medicines are somewhat limited. There is a clear need to find new effective therapies for the treatment of ET. Cannabidiol (CBD) is a modulator of CB1 receptor and CB1 agonists can reduce tremors in experimental models. We hypothesized that a single acute CBD intake would reduce tremors in ET patients. We performed a randomized, controlled, double-blind, crossover study on 19 patients with ET. They were 10 males and 9 females, had mean 63 years of age, and mean 23 years of disease duration and had insufficient control of their tremors with the usual pharmacological treatment. They ingested a single oral dose of CBD (300 mg) or placebo in two experimental sessions performed 2-weeks apart. Patients were evaluated immediately before and after oral ingestion (60 min and 210 min), using the Fahn-Tolosa-Marin clinical scale. There was no carryover effect. There were no significant differences in upper limb tremors score, specific motor task tremor scores (writing and drawing/pouring) or clinical impression of change after treatment with placebo or CBD. In conclusion, a single 300 mg oral dose of CBD had no significant effect on the severity of upper limb tremors of ET patients. Our findings did not exclude the possibility that chronic treatment with CBD could have a symptomatic effect.

Dystonia is a relatively common movement disorder but some of its epidemiological and clinical aspects have not been well characterized in Brazilian patients. Also, a new clinical classification for the disorder has been proposed and its impact on clinical practice is unclear. We aimed to describe the clinical and demographic characteristics of a Brazilian series of patients with primary dystonia, to estimate its local prevalence, and to explore the impact of using a new classification for dystonia. We identified 289 patients with primary dystonia over a 12-month period, of whom235 underwent a detailed evaluation. Patients with primary dystoniamade up one-sixth of all patients evaluated at the service where the study was conducted, with an estimated local prevalence of 19.8/100,000 inhabitants. The clinical and demographic characteristics of the patients were similar to those described elsewhere, with blepharospasm as the most common focal dystonia and most patients using sensory tricks that they judged useful on a day-to-day basis. The application of the new classification was easy and simple, and the systematic approach allowed for a better clinical characterization of our patients. We recognized two dystonic syndromes that were not described in the original article that proposed the classification, and suspected that the arbitrary distinction between generalized and multifocal dystonia seems not to be useful for patients with primary dystonia. In conclusion, the prevalence and clinical characteristics of our patients were not distinct from other studies and the new classification was shown to be practical and useful to characterize patients with dystonia.