Objective: To evaluate obsessive-compulsive symptomatology in functional and organic dystonia

Background: Case-control studies have reported elevated rates of obsessive-compulsion in genetic (DYT11 and DYT5) and some idiopathic focal dystonias. Functional imaging data demonstrate partially overlapping patterns of cortico-striatal activity in dystonia and obsessive-compulsive disorder (OCD). An imbalance in transmission through direct and indirect pathways within the basal ganglia may contribute to the premotor cortical hyperactivity observed in OCD, functional and organic dystonia. The idea that functional motor disorders might share common pathophysiology with OCD has a longer tradition—writing in nineteenth century, the French neurologist Pierre Janet drew parallels between “la folie du doute” and hysteria.

Methods: Thirty-three patients with organic dystonia (24 idiopathic, 5 genetic, 4 secondary), 13 with functional dystonia (all met the DSM-V criteria for a functional neurological disorder) and 28 healthy sex-matched controls participated in this study. They completed self-rating scales for obsessive-compulsion: the Yale-Brown Obsessive Compulsive Scale (YBOCS) or the Brief Obsessive Compulsive Scale (a shortened version of the Y-BOCS). Scores were divided evenly to yield five categories of severity—subclinical (0), mild (1), moderate (2), severe (3) and extreme (4). Data was analysed for statistical significance, using SPSS software, by Kruskal-Wallis test followed by post hoc pairwise comparisons using the Dunn-Bonferroni approach.

Results: Scores for obsessive-compulsion differed significantly across the groups. 39% of functional patients scored two (moderate) or above, compared with 9% for organic patients and 0% for healthy controls. Pairwise comparisons demonstrated a significant difference between the two dystonia groups, with higher scores in the functional group (p = 0.02). Control subjects’ scores differed significantly from functional (p = 0.003) but not organic dystonia.

Conclusions: Rates of obsessive-compulsion are higher in patients with functional dystonia than those with organic causation. There is evidence that abnormal motor expectation defines functional movement disorders. Obsession-compulsion may be contributing to altered cortico-striatal dynamics that lower the threshold for their formation in functional dystonia.

References: 1. Schrag AE, Mehta AR, Bhatia KP, et al. The functional neuroimaging correlates of psychogenic versus organic dystonia. Brain 2013: 136; 770–781. 2. Nakao T, Okada K, Kamba S. Neurobiological model of obsessive–compulsive disorder: Evidence from recent neuropsychological and neuroimaging findings. Psychiatry Clinic Neurosci 2014: 68: 587–605.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/higher-self-rated-obsessive-compulsion-in-functional-compared-with-organic-dystonia/