Functional Magnetic Resonance - and Diffusion Tensor Imaging Investigations of Pure Adult Gilles de la Tourette Syndrome

Gilles de la Tourette syndrome (GTS) is a chronic neuropsychiatric disorder characterized by multiple motor and vocal tics, affecting approximately 1% of the population. The precise neuropathology of GTS has not yet been delineated, but current models implicate subcortical and cortical areas - the cortico-striato-thalamo-cortical (CSTC) circuit. The majority of studies in the literature have either dealt with GTS with comorbid conditions and/or children with GTS. As these factors are known to affect brain structure and function, it unknown what the neurobiological underpinnings of pure adult GTS are. The objective of this body of work was to use functional magnetic resonance imaging (fMRI) and diffusion tensor imaging (DTI) to characterize differences in brain function and structure in pure adult GTS patients versus age- and sex-matched controls. I employed a series of three distinct analyses for this purpose, based upon current models of CSTC circuit-related dysfunction in GTS. In the first, GTS patients and control participants executed three finger-tapping paradigms that varied in both complexity and memory requirements. These finger-tapping tasks were modeled after previous studies that showed CSTC circuit-related activity in healthy individuals. Using a multivariate statistical technique to assess task-related patterns of activation across the whole brain, I found that, while there was much overlap in brain activation patterns between groups, sensorimotor cortical regions were differentially recruited by GTS patients compared to controls. In the second fMRI analysis, I measured low-frequency spontaneous fluctuations of the blood oxygen level dependent signal during rest, and found that GTS patients exhibited greater resting state functional connectivity with the left putamen compared to controls. In the final analysis, DTI was used to provide a whole-brain assessment of regional diffusion anisotropy in GTS patients and healthy volunteers and to investigate the fractional anisotropy in predetermined ROIs. This analysis found no differences between GTS patients and controls. Overall, my findings indicated that several CSTC-related regions shown to be atypical in GTS patients previously, are also atypical in pure adult GTS, and that sensorimotor cortical regions and the putamen may be regions of functional disturbance in pure adult GTS.Ph