Psychiatric disorders in idiopathic-isolated focal dystonia

Idiopathic-isolated focal dystonia (IIFD) is a movement disorder characterised by involuntary, sustained muscle contractions, leading to abnormal postures. Psychopathology is frequent in patients with IIFD, and while traditionally this was thought to be a secondary phenomenon, there is emerging evidence for shared neurobiological mechanisms. We conducted a single-centre cross-sectional study of 103 consecutive patients with IIFD and two comparison groups: 78 consecutive patients with hemifacial spasm (HFS) and 93 healthy control subjects. Assessments with regard to psychiatric disturbances were performed using self-report questionnaires, including the self-report version of the Yale-Brown Obsessive Compulsive Scale (Y-BOCS-SR), the Beck Anxiety Inventory (BAI), and the Beck Depression Inventory (BDI). Compared to healthy control subjects and patients with HFS, the IIFD group had higher OCS, anxiety, and depression scores as measured by the Y-BOCS-SR, BAI, and BDI, respectively. The Y-BOCS-SR, BAI, and BDI were highly correlated across all the subjects. Logistic regression analysis showed that the main driver of high obsessive-compulsive symptom scores, irrespective of neurological diagnosis, was the BDI, whereas it was BAI (and not BDI), that drives the association between the psychiatric rating scale scores and the neurological diagnosis. Our findings suggest that while clinically significant obsessive-compulsive symptoms are over-represented in IIFD patients relative to controls, the BAI may have better discriminatory power to distinguish between the psychiatric symptoms in IIFD patients.