White matter alterations in drug-naïve children with Tourette syndrome and obsessive-compulsive disorder

Area of Science:

• Neuroimaging
• Developmental Neuroscience
• Pediatric Neurology

Background:

• Tourette syndrome (TS) and early-onset obsessive-compulsive disorder (OCD) are frequently co-occurring conditions.
• Their shared pathophysiology and distinct clinical presentations suggest a complex relationship within a potential disease spectrum.
• Understanding early white matter (WM) changes is crucial for differentiating these conditions.

Purpose of the Study:

• To investigate and compare early structural white matter (WM) changes in drug-naïve children with TS-pure, TS+OCD, and OCD using diffusion tensor imaging (DTI).
• To identify distinct pathophysiological patterns associated with each condition and their relationship to symptom severity.
• To evaluate whether TS+OCD represents a distinct subtype of TS or shares mechanisms with OCD.

Main Methods:

• Diffusion Tensor Imaging (DTI) was employed to analyze white matter microstructure in four groups: TS-pure, TS+OCD, OCD, and age-matched controls.
• Five key white matter tracts were assessed: cortico-spinal tract (CST), anterior thalamic radiations (ATR), inferior longitudinal fasciculus (ILF), corpus callosum (CC), and cingulum.
• Fractional anisotropy (FA) values were analyzed, and correlations between DTI metrics and clinical symptom severity were evaluated.

Main Results:

• Children with TS-pure and TS+OCD exhibited increased FA in CST, ATR, ILF, and CC compared to controls, with decreased FA correlating with tic severity.
• In contrast, children with OCD showed decreased FA across most analyzed WM tracts (excluding the cingulum) compared to controls, negatively correlating with symptom severity.
• Distinct patterns of early white matter microstructural alterations were observed between TS-pure/TS+OCD and OCD groups.

Conclusions:

• The findings support the conceptualization of TS+OCD as a subtype of Tourette syndrome, characterized by specific white matter alterations.
• Obsessive-compulsive disorder appears to involve independent pathophysiological mechanisms affecting white matter development.
• Early DTI can differentiate between these related but distinct neurodevelopmental conditions.