Brain changes in Gilles de la Tourette syndrome: a systematic literature review of morphometric MRI studies

Background: Gilles de la Tourette syndrome (GTS) is a neurodevelopmental disorder characterized by chronic vocal and motor tics. Although the exact pathophysiology of GTS is poorly understood, preliminary evidence points towards alterations within the cortico-striato-thalamo-cortical pathways. Objective: Based on the hypothesis that functional abnormalities could reflect structural changes, we conducted a systematic literature review of morphometric MRI studies in children and adult patients with GTS. Method: Our systematic literature review followed the instructions provided by the Prisma guidelines and included computerized literature searches of relevant databases (PubMed, Sumsearch, Cochrane, Web of Science). Results: Thirty-seven papers were identified, and review of findings showed a number of brain regions to be potentially involved in GTS pathophysiology. Most studies identified structural changes in specific cortical areas including (sensorimotor, prefrontal, temporal, parieto-occipital cortex plus cingulate gyrus, and operculum), basal ganglia (caudate and lenticular nuclei), thalamic nuclei (ventrolateral, ventroposterior, ventroposterolateral, pulvinar), corpus callosum, midbrain and cerebellum, with variable morphological features across different studies. Conclusions: The results of our systematic review suggest, that specific structural brain changes are detectable in groups of patients with GTS; however, these abnormalities appear to be widespread and inconsistent across different studies. Most studies are limited by the relatively small sample sizes and the lack of rigorous protocols for data collection and analysis. Future morphometric investigations should include standardized clinical characterizations and longitudinal protocols, in order to account for the presence of co-morbid psychiatric disorders and the variability in the clinical course of GTS.