\citep{30561518}
Motor timing in TS \cite{Martino2019}
Maigaard and colleagues studied the ability of children with TS to suppress quick but inappropriate rewards \citep{31103639}. Not surprisingly, children with ADHD did poorly on this task, but children with TS actually did better than healthy control children. All groups improved their accuracy when a reward was promised for accuracy. One hypothesis to explain these results may be that children with TS have better motor inhibition in certain tasks due to their experience withholding tics in response to premonitory urges due to social pressures. The reward effect may correspond to the known improvement in tic suppression in the presence of immediate rewards \citep{29875706,31241402}.

Treatment

Psychological interventions

In a large study of manualized CBT in children with OCD, anxious and depressive symptoms improved substantially and were not linked to improvements in OCD severity \citep{Rozenman2019}. This result is one more argument in favor of psychotherapy for obsessions and compulsions, which are common in people with tics. A consensus report argues strongly for early intervention in OCD \citep{30773387}. Since early-onset OCD is associated with tics \cite{21820387}, a similar argument could be made for early intervention in tic disorders, especially since effective behavioral treatments without side effects are available. Studies of whether early intervention changes the course of tic disorders are needed. 
One of the most interesting possibilities in delivering behavior therapy for tics has come from the development of internet-based platforms, making these approaches available for a large number of patients, even in remote areas. The BIP-TIC platform, developed in Sweden, allows to use either HRT, ERP or a mixture of both online with a possible intervention of a therapist by phone or email. A first pilot study on 23 patients has shown encouraging results in a rater-blind parallel group trial (including a 12 month follow up) \citep{30772854}. A large (n= +200) UK-based study of ERP using this platform, called ORBIT, will commence shortly \citep{30610027}.  
Another way to increase the number of patients to be reached by CBT is group therapy. A Danish study, using a combined HRT/ERP approach has demonstrated that it is equally effective in a group as in an individual setting with 27 patients per treatment arm \citep{Nissen2019}. This represents a promising and interesting way forward in CBT for tics.
 

Medication

First things first: the American Academy of Neurology (AAN) practice guidelines for TS \citep{31061208}\citep{31061209} are one of the most important publications in our field for the 2019. A detailed analysis goes way beyond the scope of this review but it might be worth noting that the only "high confidence in the evidence" rating was awarded to Comprehensive Behavioral Intervention for Tics (CBIT) and not pharmacological or surgical therapies for tics. This represents a true paradigm shift in the field. Similar conclusions were drawn in another review of evidence-based treatments for TS and CTD \citep{31295410}.
In recent years, cannabis and cannabis-derived products are being considered for the treatment of tics – and a variety of other movement disorders. Milosev et al. \citep{Milosev2019} present results from a retrospective data analysis and an online survey on the use of cannabis-based medicine for tics and comorbidities in TS. Patients (n= 98 and 40) expressed a preference for medical cannabis (rich in THC) over dronabinol and nabiximols. However, results from large randomized trials are still awaited and will help guide therapeutic decisions. These will also depend, obviously, on the availability of different cannabis-based medications across countries.

Neurosurgery

Blocking tics by behavior therapy or botulinum toxin has been hypothesized to interrupt the sensory-motor feedforward loop likely operating in TS, i.e. premonitory sensations triggering tics which then re-inforce premonitory sensations. Kimura et al. \citep{Kimura2019} report on four patients who had undergone thalamic DBS for severe TS. In two, DBS could be completely withdrawn four and seven years after surgery, respectively, without re-increase in tics. This is intriguing and confirms unpublished reports from other centers, including our own (Paris). One major question in this regard is, of course, if the tics observed pre-op were purely organic of if some functional tics were also present. On the topic of functional tics, which are occasionally seen by specialists, Ganos et al. \citep{Ganos2019} have published a landmark review which should be compulsory reading in the field.
In a 48 month follow-up of a multicentre trial comprising 16 severe TS patients treated with DBS of the anterior pallidum, it was found that 75% of subjects were treatment responders, that YGTSS (-40%) and global functioning scores decreased significantly, and that self-injurious behaviors ceased in all affected (n=7) patients \citep{Welter2019}. Also, no persistent psychiatric or neurological side effects were noted. However, DBS did not lead to overall decrease in medication. Predictors of long term outcome for DBS in TS are still needed and larger, perhaps international studies will be able to fill that gap. One step towards that was signalled by a report of initial results from an international TS-DBS registry relating DBS active contact location to outcomes \citep{Johnson2019}.