Segmental and Multifocal Isolated Dystonias: Similarities and Differences

Background: Whether the traditional distinction between segmental and multifocal dystonia is clinically or scientifically useful remains unclear. Objective: To evaluate whether idiopathic isolated adult-onset segmental and multifocal dystonia can be differentiated based on clinical features other than the contiguity of affected body regions. Methods: We compared data on segmental and multifocal dystonia from two large dystonia databases established in the USA and Italy that used similar criteria for patient recruitment and assessment. Results: Compared to segmental dystonia, multifocal dystonia was characterized by a higher proportion of men, a younger age at dystonia onset, a greater frequency of upper limb dystonia, and a lower frequency of cranial dystonia at both onset and last examination. Segmental and multifocal dystonia had a similar frequency of alleviating maneuvers, non-motor eye symptoms in blepharospasm, and neck pain and tremor in cervical dystonia. Although the initial spread pattern from focal to segmental or multifocal appeared faster in the segmental dystonia group, adjusting the analysis for the initial body site involved revealed no significant differences between the two groups. Segmental and multifocal dystonia starting in the same body site showed similar age, sex, and spread characteristics. The observed differences and similarities were consistent across both independent databases. Conclusions: Segmental and multifocal dystonia share differences and similarities. The observed differences may reflect a difference in the predominant site of dystonia onset. From a clinical perspective, therefore, the segmental/multifocal distinction is probably not valuable in the dystonia classification scheme, although further data may be needed from a pathophysiological perspective.