Pathophysiology
Animal models
Benzodiazepines and ethanol are among the well-known positive allosteric modulators (PAMs) of GABA-A receptors. A PAM highly selective for GABA-A receptors containing α6 subunits showed efficacy in the D1CT-7 transgenic mouse model of tics \citep{33525455}. Dopamine antagonists show similar effects but induce catalepsy, whereas this PAM did not. These results suggest strategies for future human studies including for treatment of tic disorders.
Pathological studies
Electrophysiology
\citep{33949779}
A patient was treated for major depressive disorder with bilateral ventral internal capsule and ventral striatum DBS and developed dose-dependent (voltage-dependent) coprolalia and limb movements, along with changes in affect, mood and memory \citep{33568978}. Inpatient observation supported the conclusion that these symptoms were most likely caused by the focal electrical stimulation. Although a single case, this report adds to previous data implicating primarily subcortical nuclei in secondary tic disorders.
Dual-site TMS and diffusion tensor imaging showed loss of normal prefrontal (pre-SMA) inhibition of motor cortex in 12 children with TS/CTD compared to 14 control participants \citep{33462641}. The decreased inhibition correlated to impairment of tic inhibition. Increased fractional anisotropy was also observed in several white matter pathways in TS/CTD. These results support similar previous findings in adults with TS and support a plausible pathophysiological mechanism relevant to tic persistence.
Two articles
here from early 2021
Neuroimaging studies
Pharmacological studies
Clinical and neuropsychological studies
Other
Treatment
Psychological interventions
A group therapy study compared CBIT to a control condition with education about tics \citep{33415472}. Group CBIT better reduced tics, especially at 3 months after the intervention. Children with behavioral problems had less improvement, whereas higher intellectual functioning portended better results. This report adds to previous suggestions that group therapy—which can reach more patients at lower cost—is an effective way to deliver CBIT.
Medication
Neurosurgery