Elan D Louis1,2,3, Eina H Eliasen4, Christine Y Kim5,6, Monica Ferrer5, Shahin Gaini7,8,9, Maria Skaalum Petersen4,7. 1. Department of Neurology, Yale School of Medicine, Yale University, New Haven, Connecticut, USA, elan.louis@yale.edu. 2. Department of Chronic Disease Epidemiology, Yale School of Public Health, Yale University, New Haven, Connecticut, USA, elan.louis@yale.edu. 3. Center for Neuroepidemiology and Clinical Neurological Research, Yale School of Medicine, Yale University, New Haven, Connecticut, USA, elan.louis@yale.edu. 4. Department of Occupational Medicine and Public Health, The Faroese Hospital System, Tórshavn, Faeroe Islands. 5. Department of Neurology, Yale School of Medicine, Yale University, New Haven, Connecticut, USA. 6. Center for Neuroepidemiology and Clinical Neurological Research, Yale School of Medicine, Yale University, New Haven, Connecticut, USA. 7. Centre for Health Science, Faculty of Health Sciences, University of the Faroe Islands, Tórshavn, Faeroe Islands. 8. Division of Infectious Diseases, National Hospital Faroe Islands, Tórshavn, Faeroe Islands. 9. Department of Infectious Diseases, Odense University Hospital/University of Southern Denmark, Odense, Denmark.
Abstract
BACKGROUND: There are fewer than 5 population-based studies of dystonia worldwide. Only one utilized a movement disorders neurologist. Given the potential for founder effects, and the highly genetic nature of dystonia, the Faroe Islands provide a particularly interesting setting to study the prevalence of dystonia. OBJECTIVE: To estimate the prevalence of dystonia. METHODS: We used a 2-phase, population-based design, screening 1,334 randomly selected Faroese individuals aged ≥40 years from which a subsample of 227 participated in an in-person clinical evaluation. Dystonia was assessed by 2 movement disorder neurologists using videotaped examinations. RESULTS: Two of 227 (0.88%, 95% CI -0.33 to 2.09%) were diagnosed with cervical or segmental dystonia. An unusual form of thumb flexion dystonia was noted in 75 more, yielding a combined prevalence of 33.92% (95% CI 27.73-40.11%). CONCLUSIONS: The prevalence of cervical or segmental dystonia was as high as in one prior population-based study using similar methods. Furthermore, an unusual form of thumb flexion dystonia was uncovered, which yielded an extraordinarily high prevalence of dystonia in this population. Although our methods likely contributed to more complete capture of subtle dystonia, founder effects are highly likely to have been an additional major contributor to these findings.
BACKGROUND: There are fewer than 5 population-based studies of dystonia worldwide. Only one utilized a movement disorders neurologist. Given the potential for founder effects, and the highly genetic nature of dystonia, the Faroe Islands provide a particularly interesting setting to study the prevalence of dystonia. OBJECTIVE: To estimate the prevalence of dystonia. METHODS: We used a 2-phase, population-based design, screening 1,334 randomly selected Faroese individuals aged ≥40 years from which a subsample of 227 participated in an in-person clinical evaluation. Dystonia was assessed by 2 movement disorder neurologists using videotaped examinations. RESULTS: Two of 227 (0.88%, 95% CI -0.33 to 2.09%) were diagnosed with cervical or segmental dystonia. An unusual form of thumb flexion dystonia was noted in 75 more, yielding a combined prevalence of 33.92% (95% CI 27.73-40.11%). CONCLUSIONS: The prevalence of cervical or segmental dystonia was as high as in one prior population-based study using similar methods. Furthermore, an unusual form of thumb flexion dystonia was uncovered, which yielded an extraordinarily high prevalence of dystonia in this population. Although our methods likely contributed to more complete capture of subtle dystonia, founder effects are highly likely to have been an additional major contributor to these findings.
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