Neuroimaging of tic disorders

Gilles de la Tourette syndrome (GTS) is increasingly conceptualized as a neurodevelopmental network disorder. In this chapter, we have synthesized two decades of neuroimaging findings spanning gray- and white-matter morphology, structural connectivity, and functional network dynamics in GTS across childhood and adulthood. Structural MRI studies using voxel-based morphometry (VBM) have reported heterogeneous volume differences-both decreases and increases-across cortico-striatal-thalamo-cortical regions, motivating the use of meta-analytic approaches to identify more consistent loci, including cingulate, sensorimotor, thalamic, striatal, and insular regions. In contrast, cortical thickness studies more consistently indicate cortical thinning in motor/premotor and prefrontal areas, with links to tic phenomenology and premonitory urges. Diffusion and volumetric white-matter measures further implicate interhemispheric pathways and fronto-striatal projections, with some indices relating to tic severity. At the circuit level, tractography and structural covariance studies support altered connectivity within the cortico-striato-pallido-thalamo-cortical loop and highlight a complementary contribution of cerebello-cortical pathways. Functional MRI studies converge on temporally structured node engagement during tic generation-preceding activity in supplementary motor, cingulate, insular, and opercular regions, followed by sensorimotor, thalamic, and cerebellar involvement-and reveal large-scale reconfiguration of cortico-basal ganglia networks associated with tic severity and comorbid symptoms. Finally, lesion-network mapping and coordinate-based network mapping studies in secondary tics and GTS-related atrophy converge on a common tic-associated network, providing a translational framework to guide neuromodulation and to derive clinically meaningful network biomarkers for treatment targeting.