Performance and ERPs in a flanker task \citep{28659750}.
Machine learning was applied to functional connectivity fMRI data \citep{28478510}.
Too few neuroimaging studies investigate functional neuroanatomy using focal chemical effects as stimuli. A very compelling study used positron emission tomography (PET) to investigate the regionally specific effects of focal GPe disinhibition on downstream cortical activity \citep{27989846}. The GABAA antagonist bicuculline was injected into different regions of the macaque external globus pallidus (GPe) that previous studies had previously linked to dyskinesias, hyperactivity, and repetitive behavior. FDG (18F-2-fluoro-2-deoxy-D-glucose) PET was used
GABA concentrations in M1/S1 by MR spectroscopy, and TMS measures putatively influenced by GABA, in the same (control) subjects \citep{28284797}.
\citet{Mills_2017} describe a 22-year-old man with schizophrenia who developed tics on olanzapine after tapering risperidone. The authors are appropriately cautious in presenting this as a possible case of secondary tics, but given that many people with tics are unaware of the diagnosis, and the fact that olanzapine on average effectively treats tics, this case is much more likely to represent a previously undiagnosed primary tic disorder than a side effect of olanzapine.
Conclusions
2017 has again seen a rise in publications on TS and reflects the increased interest this field receives, both from clinicians and researchers devoted to this disorder but also from adjoining fields, given the substantial psychopathology associated with tics.
One important question raised is the natural course of TS and the rate of (non-)remission. Recent data suggest that the optimistic outlook prevalent with regard to tic severity when gliding from adolescence into adulthood might not be justified. Here, large longitudinal studies are warranted, also to better understand the prognostic factors associated with tic remission or persistence. The fate of comorbidities also needs to be better understood, even though data have begun to emerge.
We also still face important delays in the diagnosis of TS, and we need to deal with the recently demonstrated increased suicide risk in this condition, which underlines that tic disorders are far from benign.
Of note, there is a rise in computational models of TS which provide important leads to understanding its pathophysiology and will likely fuel more targeted treatment approaches for tics. In the therapy field, 2017 has mainly seen studies centered on well-known pharmacological targets such as the dopaminergic system; however, new antidopaminergic medications were studied or came to the market in 2017, and increasing data supports existing off-label prescription practices. Behavioral therapy continues to emerge as a main pillar of tic treatment, with an improved understanding of its mechanisms and response factors. In the surgical field, deep brain stimulation for severe TS cases continues to draw interest ; in particular, target choice, length of stimulator programming for optimal outcome, and closed-loop systems are under active investigation.
Overall, the field is active and burgeoning. Breakthroughs are to be expected in the upcoming years, especially with regard to large-scale efforts in the field.