Objective: To assess state-dependent cerebellar-cortical connectivity, through transcranial magnetic stimulation (TMS), in adult patients with Tourette Syndrome (TS) during a voluntary tic inhibition task. A secondary objective was to evaluate associations between this connectivity and relevant clinical features of TS, such as tic severity and comorbidities.

Background: The mechanisms involved in the generation of tics and their suppression in TS are not fully understood [1]. Previous brain imaging studies in drug-naïve children with TS suggest an early impairment in cerebellar structural and functional connections, especially within cerebello-thalamo-cortical (CTC) [2]. However, compensatory neural adaptations can occur as more control over tics is gained [3]. Here, we are interested in knowing how voluntary tic inhibition alters the inhibitory tone that the cerebellum exerts on the primary motor cortex, known as cerebellar brain inhibition (CBI).

Method: Seventeen adult patients with TS and 32 demographically matched healthy volunteers participated in the study. CBI was assessed in both groups under two conditions, during voluntary tic inhibition and free ticcing. The conditioning stimulus was administered to the right cerebellum before a test stimulus (TS) was administered to the left M1 by interstimulus intervals (ISI) of 3 or 5 ms [4]. Also, a standard clinical evaluation was applied that included scales for tic severity (YGTSS), evaluation of frequency and severity of premonitory urges (PUTS), and psychiatric comorbidities (Y-BOCS and the Adult ADHD Self-Report Screening Scale for DSM-5).

Results: All TS participants could suppress voluntarily most of their tics. Significant CBI was found in healthy controls that was not observed in the TS group, obtaining significant differences between groups in both ISI. This lack of CBI in patients was not modified by the voluntary tic inhibition task. CBI was significantly correlated with YGSST and a trend-level correlation with the Y-BOCS obsession subscale.

Conclusion: CBI does not mediate voluntary inhibition of the tic in adult TS. Rather, our data suggest that the impairment of cerebellar-cortical connectivity described in children persists in adult TS. Cerebellar structural and functional connections could play a significant role in TS severity.

References: [1] Ganos C, Rothwell J, Haggard P. Voluntary inhibitory motor control over involuntary tic movements. Mov Disord. 2018 Jul;33(6):937-946. doi: 10.1002/mds.27346.

[2] Tikoo S, Suppa A, Tommasin S, Giannì C, Conte G, Mirabella G, Cardona F, Pantano P. The Cerebellum in Drug-naive Children with Tourette Syndrome and Obsessive-Compulsive Disorder. Cerebellum. 2021 Sep 30. doi: 10.1007/s12311-021-01327-7.

[3] Stephen R. Jackson, Amy Parkinson, Jeyoung Jung, Suzanne E. Ryan, Paul S. Morgan, Chris Hollis, Georgina M. Jackson. Compensatory Neural Reorganization in Tourette Syndrome. Curr Biol. 2011 Apr 12; 21(7): 580–585. doi: 10.1016/j.cub.2011.02.047

[4] Carrillo F, Palomar FJ, Conde V, Diaz-Corrales FJ, Porcacchia P, Fernández-Del-Olmo M, Koch G, Mir P. Study of cerebello-thalamocortical pathway by transcranial magnetic stimulation in Parkinson’s disease. Brain Stimul. 2013 Jul;6(4):582-9. doi: 10.1016/j.brs.2012.12.004.

« Back to 2022 International Congress

MDS Abstracts - https://www.mdsabstracts.org/abstract/role-of-the-cerebellocortical-pathway-in-the-pathophysiology-of-adult-with-tourettes-syndrome/