Objective: Movement disorders (MD) have been described in demyelinating diseases, especially in multiple sclerosis (MS). Paroxysmal dystonia, also called tonic spasm (TS) is the most frequent MD in MS. Only few cases have been reported in Neuromyelitis optica (NMO) albeit it’s frequently referred by these patients. For this reason, we decided to study more deeply the characteristics of this abnormal movement in NMO. Background: It has been suggested that spinal cord pathology predominantly affecting the inhibitory interneurones may result in abnormal activation of the antagonistic muscles resulting in dystonic-athetotic posturing. Even though the pathophysiological mechanisms of TS remain unclear, the most widely accepted hypothesis is that they occur by a transversely spreading ephaptic activation of axons within a demyelinating plaque, at any level in a motor path. Methods: We recruited 19 patients (P) with relapsing NMO seen at the Ramos Mejia Hospital in Argentina. NMO was diagnosed by the Wingerchuk?s criteria. Eigthteen women; aged between 23-53 ys. We performed them an interview, a physical exam and reviewed their clinical records. Three patients with TS were excluded because of irregular follow up. Results: Fourteen /16 P developed TS during their illness. Of the two P without spasms, one had myasthenia gravis, and the other one had a very benign disease. Most spasms involved an hemibody or lower extremities. Trunk, neck and face were also affected in 3 P with a more severe disease. Twelve /14 had sensory symptoms preceding or accompanying the TS, tipically a burning pain. Triggers usually were sudden movements and emotions. The severity, frequency and duration of the TS were worst during disease relapses. No correlation was observed between the severity of the spasms and spasticity (Modified Ashworth scale). Coexisting spasms and hypotonia was observed during acute myelitis. All P, except one, required pharmacological treatment. Most of them were treated with low doses of carbamazepine with excellent response. Acetazolamide was used in 2 P also with good results. Conclusions: The frequency of paroxysmal dystonia in this group of patients was high and the severity was worst during active disease. Spasms occurred in a stereotypical fashion and sometimes were disabling, but with good response to pharmacological treatment. Carbamazepine proved to be an effective drug.
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