Treatment
Psychological interventions
Behavior therapy (BT) is considered to be the first line treatment since publication of the 2019 AAN guidelines, based on controlled randomized trials. In a naturalistic setting (children and adolescents with chronic tics, n=74) and over a 12 month follow-up period, it could be demonstrated that BT is and remains effective in 75% of patients analyzed, attesting not only to its efficacy but durability \citep{Andrén2021}.
Internet-based BT programs are investigated by multiple groups to make BT available to a larger number of patients, rendering it thus independent on the availability of trained practitioners and financial considerations in countries where psychotherapy is not reimbursed by social security. Rachamin et al. offer preliminary data on internet-based guided self-help comprehensive behavioral intervention for tics (I-CBIT) in 25 youths (passive control group/waiting list, n=16), and show this approach to be both effective and well received over a 6 month period. Larger trials including an active control group are necessary to confirm these first positive results \citep{Rachamim2020}.
Another way to increase access to BT for tic treatment is group training. The "Tackle your Tics" program is an intensive four day course based on an enhanced version of ERP (exposure and response prevention). First results in 13 youth offer promising results regarding tic reduction and increased quality of life, with a two month follow-up period. Larger controlled trials with longer follow-up periods are awaited awaited \citep{RN10144a}.
Still another approach is to train parents as therapists. For that purpose, an instructional video guide (on DVD) based on habit reversal training was developed and applied (n=33), and compared to in-person training (n=11) in children (mean age 10 years). Home-based, parent-administered HRT was as efficacious for tic reduction as traditional in-person training. However, the drop out rate in the former group was close to 50%, so that the authors advocate regular phone contacts during the DVD treatment course, which squares with other hybrid formats such at BipTic \citep{Singer2020}.
A very small (n=3) case series on an interesting new BT technique based on attention training to suppress tics: to be followed \citep{Schaich2020}.
So far, BT is usually proposed for children above the age of ten. In this very interesting proof of concept study, Bennett et al. test a CBIT format for children ages 5-8 (n=16) and show good response (tic reduction) and acceptance. Moreover, they monitor these improvements over a one year period and speculate that early BT might alter the chronic course of tics: this is a very important subject and should be investigated in larger, longitudinal cohorts \citep{Bennett2020}.
Remarkably, comprehensive behavior intervention for tics (CBIT) was shown as also normalizing inhibitory control in a specific task of perception-action bindings \citep{Petruo_2020}.
Neurosurgery
An Italian center reports their experience with anterior GPi vs. Cm-Pf DBS for TS \citep{32429219}. Forty-one TS patients had DBS in ventro-oralis / centromedian-parafascicular thalamus and 14 had DBS in anteromedial GPi. The authors followed them for 4 years. YGTSS and Y-BOCS improved in both groups (p<.001), but Y-BOCS improved more in the GPi group. Hardware removal was limited to the thalamic DBS group (13/41, vs. 0/14 in the GPi group).
The DBS registry (n=66 bilateral GPi, n=32 centromedian [Cm] thalamus) has provided additional important information \citep{32653920}. Probabilistic tractography from estimated volumes of tissue activated (VTAs) was used to identify networks correlated with improvement in tics or OCD symptoms. Cleverly, these networks were in turn used as seed regions for “reverse” tractography to identify local "hot spots" and "cold spots." For GPi targets, connectivity to limbic and associative networks, caudate, thalamus and cerebellum predicted clinical improvement scores. The anteromedial GPi showed higher connectivity to this network, and the extent to which estimated VTA overlapped with this anteromedial region correlated with tic improvement. For Cm targets, connectivity to sensorimotor and parietal-temporal-occipital networks, putamen and cerebellum correlated with tic improvement. The anterior/lateral part of the Cm region was more highly connected to this network. For both sites, connectivity to prefrontal, orbitofrontal and cingulate cortex correlated with OCD improvement. These results suggest that structural connections of focal stimulation sites to specific networks may lead to clinical benefit. Interestingly, the identified networks may differ not only by symptom but also based on the surgical target region.