Objective: Case-control study investigating clinical characteristics associated with functional dystonia (FDys) and comparison to matched patients with primary other dystonia (ODys) within a US specialized dystonia clinic.

Background: FDys is a poorly understood, under-recognized and debilitating subtype of functional movement disorder that is particularly difficult to diagnose and treat.

Methods: Medical records were reviewed for all new patient visits at a mixed adult/pediatric tertiary referral dystonia clinic from 2005-2017. 1475 consecutive new consultations were assessed and 99 met criteria for clinically-established FDys, second only to primary cervical dystonia (N=212) as the most commonly encountered condition. The FDys cohort was compared to 99 ODys control patients, which were (as possible) distribution, age and sex-matched. Functional status was assessed by the modified Rankin scale (mRS). Univariate and multivariate regression analyses were performed assessing for predictors of functional vs organic dystonia, as well as predictors of FDys symptom severity.

Results: 86 adult and 13 pediatric FDys cases were identified, with high rates of multifocal/generalized and paroxysmal dystonia. In comparison to ODys, significant (p<0.05) associations included female gender, older age of onset (particularly paroxysmal), concurrent pain, cognitive complaints, unemployed, on or pursuing disability, more likely to have a family history of psychiatric disease, more allergies, higher benzodiazepine or narcotic use, more likely to require a mobility aid, higher mean mRS (2.1 vs 1.4) and lower likelihood of improvement after ≥6 months and had unnecessary interventions. A multivariate logistic regression analysis revealed abrupt onset, stressful life event, mRS ≥2, medically unexplained symptoms, >10 medical comorbidities and depression/anxiety independently predicted FDys vs ODys (p<0.05). Linear regression in FDys revealed psychiatric symptoms, FH psychiatric illness, greater functional findings on examination, being unemployed or not in school and having ≥5 allergies were significant, independent predictors for worsening mRS (p<0.15).

Conclusions: FDys is a frequently misdiagnosed disorder and is associated with higher narcotic and benzodiazepine use. Individuals with FDys show greater physical impairments and worse outcomes than corresponding ODys patients.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/neuropsychiatric-and-prognostic-differences-between-functional-and-primary-dystonia-subtypes-in-a-us-specialized-dystonia-clinic-a-case-control-study/