Involuntary Thumb Flexion on Neurological Examination: An Unusual Form of Upper Limb Dystonia in the Faroe Islands

• Published in: Tremor and Other Hyperkinetic Movements
• Main Authors: Kim, Christine Y.; Department of Neurology, Yale School of Medicine, Yale University, New Haven, CT; Center for Neuroepidemiology and Clinical Neurological Research, Yale School of Medicine, Yale University, New Haven, CT, Petersen, Maria Skaalum; Department of Occupational Medicine and Public Health, The Faroese Hospital System, Tórshavn; Centre for Health Science, Faculty of Health Sciences, University of the Faroe Islands, Tórshavn, FO, Eliasen, Eina H.; Department of Occupational Medicine and Public Health, The Faroese Hospital System, Torshavn, Defazio, Giovanni; Department of Medical Sciences and Public Health, Neurology Unit, University of Cagliari, Cagliari, Greene, Paul; Mount Sinai School of Medicine, Movement Disorders Division, New York, NY, Jinnah, Hyder A.; Departments of Neurology, Human Genetics and Pediatrics, Emory University, Atlanta, GA, Tijssen, Marina A.J.; Department of Neurology, University Medical Centre Groningen, University of Groningen, Groningen, Louis, Elan D.; Department of Neurology, Yale School of Medicine, Yale University, New Haven, CT; Center for Neuroepidemiology and Clinical Neurological Research, Yale School of Medicine, Yale University, New Haven, CT; Department of Chronic Disease Epidemiology, Yale School of Public Health, Yale University, New Haven, CT
• Format: Article in Journal/Newspaper
• Language: English
• Published: Ubiquity Press
• Subjects: Dystonia; focal dystonia; Faroe Islands; thumb flexion; phenomenology; Thumb
• Online Access: https://tremorjournal.org/jms/article/view/460; https://doi.org/10.5334/tohm.460

Background: The prevalence of dystonia varies worldwide. A prior report suggested a high prevalence of focal dystonia in the Faroese population, possibly reflecting a founder effect. During standardized neurological examination as part of an ongoing neuroepidemiologic study in the Faroe Islands, we noted an unusual phenomenon of thumb flexion during repetitive hand movements in a subset of subjects and sought to define its phenomenology.Methods: We requested commentary from a panel of dystonia experts regarding the phenomenology of the movements. These experts reviewed the videotaped neurological examination.Results: Among the experts, dystonia was the leading diagnosis. Alternate causes were considered, but deemed less likely.Discussion: Diagnosis of dystonia requires careful clinical assessment and consideration of associated features. We report a novel form of dystonia, not previously described to our knowledge, in this isolated population. Further studies of dystonia prevalence in the Faroe Islands are merited to characterize its burden in this population and its specific clinical characteristics.