The Suppressive Effect of the Motor System on the Sensory System in Patients With Tourette Syndrome

Abstract

Objective: Tourette syndrome (TS) is a complicated sensorimotor disorder. Some patients with TS relieve their involuntary premonitory urges via tics. However, the effect of the motor system on the sensory system has not yet been elucidated. The purpose of the present study was to investigate changes in the excitability of the sensory cortex following repetitive transcranial magnetic stimulation (rTMS) of the motor cortex in patients with TS. Methods: Twenty-nine patients with TS and 20 healthy, age-matched controls were enrolled in this study. All subjects were divided into four groups: patients with rTMS, patients with sham-rTMS, controls with rTMS, and controls with sham-rTMS. The clinical severity of tics was evaluated using the Yale Global Tic Severity Scale. Single somatosensory evoked potentials (SEPs) and paired SEPs were recorded by stimulating the median nerve at the wrist of all subjects. The resting motor threshold (RMT) was tested in each subject in the rTMS group. Afterwards, all four groups were administered rTMS (1 Hz, 90% RMT) or sham-rTMS for 200 s, followed by a 15-min rest. Finally, single SEPs and paired SEPs were repeated for each subject. Results: No significant differences in RMT, the amplitudes of single SEPs, or the suppression of paired SEPs were observed between patients with TS and controls at baseline. After rTMS, a significant suppression of the peak-to-peak amplitude of the N20-P25 responses of single SEPs was observed in both controls (p = 0.049) and patients (p < 0.0001). The suppression of the N20-P25 peak-to-peak amplitude was more significant in patients than in controls (p = 0.039). A significant difference in the suppression of paired SEPs after rTMS was not observed between groups. Conclusions: The more significant suppression of N20-P25 components of single SEPs with normal suppressed paired SEPs in patients with TS after 1-Hz rTMS of the motor cortex suggests that the suppressive effect of the motor system on the sensory system might originate from the motor-sensory cortical circuits rather than the sensory system itself.

Tourette syndrome research highlights from 2020

“…Sun and colleagues explored the suppressive effect of the motor system on the sensory system in TS patients ( Sun et al . 2020 ).…”

“…Sun and colleagues explored the suppressive effect of the motor system on the sensory system in TS patients (Sun et al 2020). They used a sham-controlled repetitive Transcranial Magnetic Stimulation (rTMS) protocol (1Hz, 90% of the resting motor threshold) and recorded the somatosensory evoked potentials before and 15 minutes after rTMS.…”

Non-invasive brain stimulation as therapy: systematic review and recommendations with a focus on the treatment of Tourette syndrome

“…The lead author (KD) screened the titles and abstracts of the remaining articles using the eligibility criteria, which resulted in 24 articles for retrieval. Of these, a further 6 were excluded; 5 as they did not involve pre/post measures of tic change (Marsili et al 2017 ; Sun et al 2020 ; Suppa et al 2011 ; Suppa et al 2014 ; Wu and Gilbert 2012 ) and 1 additional case study as the participant withdrew early (Salatino et al 2014 ).…”

Transcranial Magnetic Stimulation for Obsessive-Compulsive Disorder and Tic Disorder: A Quick Review

“…A previous meta-analysis confirmed that low frequency was more effective in the treatment of TD [33], which is consistent with the results of our review. The rTMS targets were mainly the SMA, but other targets included the parietal cortex, motor area or premotor area [35,45,[54][55][56]. The review showed that the ratio of low frequency rTMS of the SMA was often used in many studies because the SMA plays an important role in the connection of the cortical, basal ganglia, and thalamic regions, which are related to the motor circuit.…”

“…Participants in half of the 12 studies received 1200 stimuli per day [35,36,42,52,53,55]. Participants in only one study underwent low frequency 200 ms stimulation [56]. The only common evaluation of all studies was based on the Yale Global Tic Severity Scale (YGTSS).…”