Environmental Risk Factors in Isolated Dystonia: A Systematic Scoping Review.

BACKGROUND

Isolated dystonia, a neurological disorder characterized by abnormal postures and repetitive movements, has a complex etiology involving both genetic and environmental factors. While genetic contributions are acknowledged, the role of environmental triggers in disease expression remains understudied.

METHODS

This scoping review adhered to the Preferred Reporting Items for Systematic reviews and Meta-Analyses Extension for Scoping Reviews (PRISMA-ScR) guidelines and systematically mapped evidence on environmental risk factors for isolated dystonia. A comprehensive search of PubMed/MEDLINE, Web of Science, and Google Scholar from the years 1980 to 2024 identified studies meeting predefined eligibility criteria. Data were extracted using standardized templates, and quality was assessed using the modified Newcastle-Ottawa Scale (NOS).

RESULTS

Nineteen studies met inclusion criteria, with NOS scores ranging from 4/9 to 8/9. Strong associations were identified between peripheral trauma and cervical dystonia (odds ratio), and between prolonged writing (>3 hours/day) and writer's cramp. Moderate associations were found between cranial trauma and blepharospasm and betel nut consumption with oromandibular dystonia. Conversely, tobacco use showed a protective effect against blepharospasm. Early-life exposures demonstrated weak or inconclusive associations, while gene-environment interactions revealed accelerated symptom onset in DYT1 mutation carriers exposed to repetitive tasks ( P = 0.03).

CONCLUSIONS

Environmental factors significantly influence the pathogenesis of isolated dystonia through circuit-specific mechanisms. Trauma, occupational exposures, and lifestyle factors emerge as key determinants. These findings highlight significant environmental determinants but also underscore the need for standardized exposure metrics and prospective investigations due to methodological heterogeneity across studies.