Examining the functional activity of different obsessive-compulsive symptom dimensions in Tourette syndrome.

Tracy Bhikram,Adrian Crawley,Paul Sandor,Paul Arnold,Elia Abi-Jaoude

doi:10.1016/j.nicl.2020.102198

Abstract

Tourette syndrome (TS) is commonly comorbid with obsessive-compulsive disorder (OCD) and many phenomenological similarities exist between tics and obsessive-compulsive symptoms (OCS). Therefore, due to the clinical importance of comorbid OCD, the goal of this study was to investigate the neural substrates of OCS in TS using functional magnetic resonance imaging. Forty patients with TS and 20 healthy controls underwent functional magnetic resonance imaging while viewing blocks of OCS-provoking pictures relating to washing, checking and symmetry symptoms, as well as generally disgusting and neutral scenes. Statistical comparisons were made between patients with moderate/severe OCS, absent/mild OCS and healthy controls. As well, within the entire TS patient group, significant associations with clinical measures were assessed for each of the provocation conditions. Group differences in the insula, sensorimotor cortex, supramarginal gyrus and visual processing regions were common among the checking, washing and disgust conditions. In the patient group, negative associations between OCS severity and activity in the supramarginal gyrus, inferior frontal gyrus, sensorimotor cortex, precuneus and visual processing regions were common among the provocation conditions. Tic severity was only associated with activity in the anterior cingulate cortex for the symmetry condition. Our findings implicate areas previously reported to be involved in OCD, as well as areas not typically implicated in OCD, suggesting that the neurobiological profile of TS+OCD is intermediate to pure TS and pure OCD.

Highlights

Tourette syndrome (TS) is characterized by the presence of tics, but for most patients with TS, “tics alone are the exception rather than the rule” (Leckman et al, 2006)
It is estimated that 86–90% of patients with TS have comorbid psychopathologies, with obsessive–compulsive disorder (OCD) and attention-deficit hyperactivity disorder (ADHD) being the most common comorbid disorders (Groth et al, 2017; Hirschtritt et al, 2015; Freeman et al, 2000)
With the exception of scores on the DS-R, the disgust propensity subscale of the DPSS, and the contamination/washing subscale of the OCI, patients had significantly higher scores for all of the clinical and behavioural instruments when compared to the control group (Table 1)

Summary

Introduction

Tourette syndrome (TS) is characterized by the presence of tics, but for most patients with TS, “tics alone are the exception rather than the rule” (Leckman et al, 2006). It is estimated that 86–90% of patients with TS have comorbid psychopathologies, with obsessive–compulsive disorder (OCD) and attention-deficit hyperactivity disorder (ADHD) being the most common comorbid disorders (Groth et al, 2017; Hirschtritt et al, 2015; Freeman et al, 2000). Often these comorbidities are more distressing than the tics and have the greatest impact on quality of life, determining the overall prognosis of TS (Rizzo et al, 2014). Factor analytic studies have divided the symptom dimensions of OCD into different subtypes including those consisting of forbidden thoughts and checking compulsions, symmetry/ordering symptoms and contamination/cleaning symptoms (Bloch et al, 2008). While there do appear to be differences in the content of OCS in TS as compared to pure OCD, many TS patients experience the full range of typical OCS including those related to contamination/cleaning and checking (Holzer et al, 1994)

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