Brander et al. \cite{Brander2019} investigated whether, at the population level, tic-related OCD has a stronger familial load than non-tic-related OCD. They found that he risk of OCD in relatives of individuals with tic-related OCD was considerably greater than the risk of OCD in relatives of individuals with non-tic-related OCD, concluding that tic-related tic-related OCD is a particularly familial subtype of OCD. The results have important implications for ongoing gene-searching efforts.

Environmental risk factors

The EMTICS study (https://cordis.europa.eu/project/id/278367/reporting?rcn=59137) was a large European multicenter trial investigating, among several subjects, the role of immunology in the etiology of tics, a long-discussed hypothesis in the context of PANS/PANDAS. A first paper on neuronal surface proteins on 188 patients with TS failed to confirm a link between pathogenic antibodies and causation of tics \cite{Baglioni2019}. In line with these findings, Baumgaertel et al. \cite{Baumgaertel2019}failed to detect autoantibodies in the CSF of 20 adult patients with TS. However, 20% of these patients had positive oligoclonal bands, an intriguing finding with no clear-cut explanation to date. Also, in the neuroimmunological field, a thoughtful review of the PANDAS/PANS controversy \cite{Gilbert2019}
\citet{30833232a}, using the National Health Insurance Research Database of Taiwan, analyzed 2261 TS patients and 20349 non-TS controls for the risk of traumatic brain injury (TBI). During follow-up, there was a significantly increased risk for TBI in TS patients compared to controls. Classic comorbidities such as ADHD, OCD and depression increased the risk for TBI, whereas the regular use of antipsychotic medication decreased it. These findings have important therapeutic implications. 

Pathophysiology

Singer and Augustine have published two excellent and exhaustive reviews on the pathophysiology  (including controversies) of tics/TS and their relevance for pharmacotherapy \citep*{30643668}\citep*{31319731}.

Electrophysiology

Spatio-temporal structure of single neuron subthalamic activity in Tourette Syndrome explored during DBS procedures \citep{Vissani_2019}.
Cued voluntary eye blinking studied by EEG in people with and without tics \citep{31382238}.

Neuroimaging studies

SERT binding increased in people with TS+OCD \citep{30700759}
fcMRI study \citep{Nielsen2020}
Alterations in basal ganglia-cerebello-thalamo-cortical connectivity and whole brain functional network topology in Tourette's syndrome \citep{31518769a} 
Insula, premonitory urges \cite{Jackson2020}
Cerebellum \cite{Sigurdsson2020}

Pharmacological studies

Impulsivity, medication and TS \cite{Atkinson-Clement2020}

Clinical and neuropsychological studies

Young adults with TS showed reduced accuracy in the second step of a reaching task, consistent with a model in which forward updating of a model of the movement is abnormal \citep{30561518}
Motor timing in TS \cite{Martino2019}
A superior ability to suppress fast inappropriate responses in children with Tourette syndrome is further improved by prospect of reward \citep{31103639}
A peek into premonitory urges in Tourette syndrome: Temporal evolution of neurophysiological oscillatory signatures \cite{Niccolai2019}
 

Treatment

Psychological interventions

In a large study of manualized CBT in children with OCD, anxious and depressive symptoms improved substantially and was not linked to improvements in OCD severity \cite{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 CBT 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 using this platform, and focussing on en ERP-based g, 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 \cite{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" was awarded to Comprehensive Behavioral Intervention for Tics (CBIT) and not pharmacological or surgical therapies for tics which is a true paradigm shift in the field. Similar conclusions were drawn in a review of evidence-based treatments for TS and CTD \citep{31295410}.
Cannabis and cannabis-derived products are being considered for the treatment of tics – and a variety of other movement disorders – with great interest over the past years. Milosev et al. \cite{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 CBT 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. \cite{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 this topic, Ganos et al. \cite{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 \cite{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, maybe international studies will be able to fill that gap. 
Image-based analysis and long-term clinical outcomes of deep brain stimulation for Tourette syndrome: a multisite study \cite{Johnson2019}