The role of the cingulate cortex in the generation of motor tics and the experience of the premonitory urge-to-tic in Tourette syndrome

Abstract

Tourette syndrome (TS) is a neurological disorder of childhood onset that is characterised by the occurrence of motor and vocal tics. TS is associated with cortical-striatal-thalamic-cortical circuit [CSTC] dysfunction and hyper-excitability of cortical limbic and motor regions that are thought to lead to the occurrence of tics.Individuals with TS often report that their tics are preceded by 'premonitory sensory/urge phenomena' (PU) that are described as uncomfortable bodily sensations that precede the execution of a tic and are experienced as a strong urge for motor discharge. While the precise role played by PU in the occurrence of tics is largely unknown, they are nonetheless of considerable theoretical and clinical importance as they form a core component of many behavioural therapies used in the treatment of tic disorders. Recent evidence indicates that the cingulate cortex may play an important role in the generation of PU in TS, and in 'urges-for-action' more generally. In the current study we utilised voxel-based morphometry (VBM) techniques, together with 'seed-to-voxel' structural covariance network (SCN) mapping, to investigate the putative role played by the cingulate cortex in the generation of motor tics and the experience of PU in a relatively large group of young people with TS. Whole-brain VBM analysis revealed that TS was associated with clusters of significantly reduced grey matter volumes bilaterally within: the orbito-frontal cortex; the cerebellum; and the anterior and mid cingulate cortex. Similarly, analysis of SCNs associated with bilateral mid-and anterior-cingulate 'seed' regions demonstrated that TS is associated with increased structural covariance primarily with the bilateral motor cerebellum; the inferior frontal cortex; and the posterior cingulate cortex.3

Tourette syndrome research highlights from 2021

“…A study using both VBM and structural covariance network mapping focused on this region. 60 This study found, first, decreased GM volume within the ACC and, second, increased structural covariance between the ACC and the motor parts of the cerebellum, the inferior frontal cortex and the posterior cingulate cortex.…”

Hippocampal volume in Provisional Tic Disorder predicts tic severity at 12-month follow-up

“…However, in the current study, these clinical subgroups (among subjects whose comorbid symptom records were available) did not differ in terms of hippocampal volume. Alternatively, the nonsignificant group difference may be due to variance with age: although Peterson et al found greater hippocampal volume in children, some subregions became smaller than in controls by adulthood [16], and reduced hippocampal volumes have been reported in adolescents [44]and in TS adults with co-morbid OCD [19]. On the other hand, the data collected using the prospective motion correction MR sequence, and with tics carefully screened by face-to-face interview, video recording of the child sitting alone, and a semi-standardized diagnostic interview (K-SADS), revealed increased hippocampal volumes in the NewTics and TS groups compared to the Tic-free group.…”