Objective: To investigate discrete structural brain networks in children and adolescents with Tourette syndrome [TS] relative to a group of matched control participants.

Background: TS is a hyperkinetic movement disorder characterised by motor and vocal tics and premonitory sensory phenomena. Symptoms of TS have been associated with imbalance of excitatory and inhibitory signalling within key cortical-basal ganglia brain circuits implicated in movement selection and habit learning [1]. The executive control network is critical for information processing during the preparation for actions [2,3] and the cerebellar Crus I area is linked in with this network. However, the role of this region in tic expression remains unknown. Here, we employed a structural covariance network [SCN] approach in a group of young people with TS.

Method: 28 TS (3 females, M_AGE=15±3y) and 36 matched controls (3 females, M_AGE=14±3y) underwent structural MRI [sMRI] scanning at the Sir Peter Mansfield Imaging Centre in Nottingham. sMRI scans were segmented using the Computational Anatomy Toolbox (CAT12). Using the resulting grey matter [GM] maps and a ‘seed-to-voxel’ approach, we computed the structural covariance between mean voxel values within the Crus 1 cerebellar region (seed) and the GM values for all other voxels in the GM maps controlling for the effects of age, sex, IQ and total intracranial volume [TIV] using a bespoke Matlab program.

Results: Our ‘seed-to-voxel’ structural covariance analysis showed greater association between the seed region and cerebellar motor areas, sensorimotor network, the mid-cingulate and dorsal anterior cingulate cortex [dACC] relative to controls. By contrast, the TS group demonstrated reduced covariance between seed and the precuneus.

Conclusion: The analysis suggests altered SCNs in young people with TS relative to a matched group of control participants. Patients with TS demonstrated greater covariance between the cerebellar crus I seed region and the dACC, a critical hub in the executive control network. Patients also demonstrated reduced covariance between the seed and the precuneus, a key area of the default mode network which further supports the impaired sense of agency in TS [5]. Our results in combination with recent animal and computational modelling studies lend further credence to the proposal that cortico-basal ganglia and cerebellar interactions play a critical role in the expression of tics.

References: [1] Albin, R. L., & Mink, J. W. (2006). Recent advances in Tourettesyndrome research.Trends in Neurosciences, 29(3), 175-182. [2] Buckner, R. L., Krienen, F. M., Castellanos, A., Diaz, J. C., & Yeo, B. T. T. (2011). The organization of the human cerebellum estimated by intrinsic functional connectivity. Journal of Neurophysiology, 106(5), 2322-2345. [3] Habas, C., Kamdar, N., Nguyen, D., Keller, K., Beckmann, C. F., Menon, V., et al. (2009). Distinct cerebellar contributions to intrinsic connectivity. The Journal of Neuroscience, 29(26), 8586-8594. [4] Alexander-Bloch, A., Giedd, J. N., & Bullmore, E. T. (2013). Imaging structural co-variance between human brain regions. Nature Reviews Neuroscience, 14(5), 322-335 [5] Delorme, C., Salvador, A., Voon, V., Roze, E., Vidailhet, M.,Hartmann, A., et al. (2016). Illusion of agency in patients with Gilles de la Tourette syndrome. Cortex, 77(April), 132-140.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/cerebellar-structural-covariance-networks-in-young-people-with-tourette-syndrome/