The Phenomenon of Exquisite Motor Control in Tic Disorders and its Pathophysiological Implications

From urges to tics in children with Tourette syndrome: associations with supplementary motor area GABA and right motor cortex physiology

Tourette syndrome (TS) is a childhood-onset disorder in which tics are often preceded by premonitory sensory urges. More severe urges correlate with worse tics and can render behavioral therapies less effective. The supplementary motor area (SMA) is a prefrontal region believed to influence tic performance. To determine whether cortical physiological properties correlate with urges and tics, we evaluated, in 8-12-year-old right-handed TS children (n = 17), correlations of urge and tic severity scores and compared both to cortical excitability (CE) and short- and long-interval cortical inhibition (SICI and LICI) in both left and right M1. We also modeled these M1 transcranial magnetic stimulation measures with SMA gamma-amino butyric acid (GABA) levels in TS and typically developing control children (n = 16). Urge intensity correlated strongly with tic scores. More severe urges correlated with lower CE and less LICI in both right and left M1. Unexpectedly, in right M1, lower CE and less LICI correlated with less severe tics. We found that SMA GABA modulation of right, but not left, M1 CE and LICI differed in TS. We conclude that in young children with TS, lower right M1 CE and LICI, modulated by SMA GABA, may reflect compensatory mechanisms to diminish tics in response to premonitory urges.

Myoclonus and other jerky movement disorders

Myoclonus and other jerky movements form a large heterogeneous group of disorders. Clinical neurophysiology studies can have an important contribution to support diagnosis but also to gain insight in the pathophysiology of different kind of jerks. This review focuses on myoclonus, tics, startle disorders, restless legs syndrome, and periodic leg movements during sleep. Myoclonus is defined as brief, shock-like movements, and subtypes can be classified based the anatomical origin. Both the clinical phenotype and the neurophysiological tests support this classification: cortical, cortical-subcortical, subcortical/non-segmental, segmental, peripheral, and functional jerks. The most important techniques used are polymyography and the combination of electromyography-electroencephalography focused on jerk-locked back-averaging, cortico-muscular coherence, and the Bereitschaftspotential. Clinically, the differential diagnosis of myoclonus includes tics, and this diagnosis is mainly based on the history with premonitory urges and the ability to suppress the tic. Electrophysiological tests are mainly applied in a research setting and include the Bereitschaftspotential, local field potentials, transcranial magnetic stimulation, and pre-pulse inhibition. Jerks due to a startling stimulus form the group of startle syndromes. This group includes disorders with an exaggerated startle reflex, such as hyperekplexia and stiff person syndrome, but also neuropsychiatric and stimulus-induced disorders. For these disorders polymyography combined with a startling stimulus can be useful to determine the pattern of muscle activation and thus the diagnosis. Assessment of symptoms in restless legs syndrome and periodic leg movements during sleep can be performed with different validated scoring criteria with the help of electromyography.

Dystonic motor and phonic tics in Tourette syndrome

BACKGROUND

Dystonic tics differ from clonic tics by their slower and more sustained nature. Dystonic tics are often present in patients with Tourette syndrome (TS) and other tic-disorders. However, their phenomenology and impact on overall impairment have not been extensively studied.

MATERIALS AND METHODS

We assessed clinical history and tic duration in video-recordings from patients with TS evaluated at our movement disorders clinic. Dystonic tics were defined as those lasting ≥ 1000 ms (ms).

RESULTS

Of the total of 201 patients with TS, there were 156 with video-recordings suitable for tic duration analysis, of their tics, 57 (36.5%) of whom had dystonic motor tics, including 9 (5.7%) with dystonic phonic tics. Dystonic motor tics had a duration range between 1033 and 15,000 ms and dystonic phonic tics between 1132 and 17,766 ms. Patients with dystonic tics were older 24.4 vs. 16.5 years (P = 0.005) and had an older age at onset 12.9 vs. 7.2 years (P < 0.001), than patients without dystonic tics. The bivariate analysis showed an association between the presence of dystonic tics, greater tic severity and wider body distribution. The multivariate regression analysis showed a statistical association with older age at evaluation (P = 0.001), greater tic severity on video-recordings (P = 0.001) and co-occurrence with complex motor tics (P = 0.020). The presence of dystonic tics increased the risk for being considered for deep brain stimulation therapy, odds ratio: 15.7 (P = 0.002).

CONCLUSION

Dystonic tics, observed in about a third of patients with TS, are associated with increased severity of TS.

The Efficacy of Cognitive Behavioral Therapy for Tic Disorder: A Meta-Analysis and a Literature Review

Background

At present, tic disorder has attracted the attention of medical researchers in many countries. More clinicians choose non-drug therapy, especially cognitive-behavioral therapy (CBT) because of the cognitive side effects of drug therapy. However, few studies had assessed its efficacy. It is necessary to have a more comprehensive understanding of the literature quality of CBT and its intervention effect.

Methods

In this study, MEDLINE, Embase, and Cochrane were searched from the beginning to June 15, 2021 to study the efficacy of -CBT on tic disorder. Only studies using the Yale Global Tic Severity Scale (YGTSS) and the control group were included.

Results

A total of 12 randomized controlled trials (RCTs), including 536 patients with tic disorders, were identified. The results showed that the effect of CBT was better than that of the control group. The pooled standardized mean difference (SMD) was −0.34 (95% CI: −0.61, −0.07). The effect size of CBT differs from different intervention conditions. In seven studies, the subjects’ motor tic scores were counted. The sample size of the experimental group was 224 and that of the control group was 218. The pooled SMD was −0.43 (95% CI: −0.75, −0.11). Seven studies counted the vocal tic scores of subjects, 224 in the experimental group and 218 in the control group. The pooled SMD was −0.22 (95% CI: −0.54, −0.11). Seven studies counted the tic impairment scores of subjects, 220 in the experimental group and 214 in the control group. The pooled SMD was −0.48 (95% CI: −0.73, −0.23).

Conclusion

The literature shows that different CBTs can significantly reduce the total score of tic disorder and the score of motor tic, but cannot significantly reduce the score of vocal tic. In the future, more new interventions were needed to improve the symptoms of different patients, especially vocal tic.

Clinical Practice Patterns in Tic Disorders Among Movement Disorder Society Members

Background

Tic disorders belong to the broad spectrum of pediatric and adult movement disorders. The wide variability in clinical presentations, applied assessment tools, and treatments are poorly understood.

Objectives

To map practices and knowledge base of movement disorder clinicians concerning clinical features, pathophysiology, and treatment approaches in tic disorders.

Methods

A 33-item survey was developed by the Tic Disorders and Tourette syndrome Study Group members of the Movement Disorder Society. The survey was distributed to the complete society membership and included responses from 346 members, 314 of whom reported treating tic disorders.

Results

Approximately one third of survey respondents (35%) frequently evaluated patients with tics. The data revealed widespread use of existing guidelines (about 70%) and screening for comorbid disorders (>90%). The most common investigations used to rule out secondary causes of tics were imaging (92%), laboratory tests (66%) and neurophysiology (38%). Functional tics were the second most common tic etiology following primary tics. Only 27% of respondents reported confidence in knowledge about tic pathogenesis. Top rated interventions to treat tics were psychoeducation, cognitive behavioral intervention for tics (CBIT) and treatment for neuropsychiatric comorbidities. Antipsychotics were ranked as the most effective pharmacologic tic intervention.

Conclusions

The majority of movement disorders specialists do not frequently encounter tics. There was sparse knowledge about tic pathophysiology. Psychoeducation, CBIT, the treatment of neuropsychiatric comorbidities and use of antipsychotics emerged as the most common interventions to treat tics. These results provide insight into what will be needed to improve the diagnosis and treatment of tic disorders.