White matter tractography in children and adolescents with TS has not been well-characterized, as previous studies utilizing diffusion tensor imaging (DTI) have primarily sampled from adult TS patients.  Sigurdsson et al. examined white matter connectivity and water diffusivity in youth with TS, and report widespread decreases in axial diffusivity \cite{Sigurdsson2018}. The authors excluded subjects with high head motion, but even small head movements can affect DTI estimates \citep{29486323}.
In an event-related fMRI study of fifteen adults with TS, successful tic suppression correlated with increased activation in dorsal anterior cingulate cortex \citep{30268027a}.  Twenty-two healthy controls performed a blink suppression task.  During voluntary blink suppression, results yielded increased activation in ventrolateral prefrontal cortex, supplementary motor area, and cingulate motor area.  These results suggest limbic system control of tic suppression, in contrast to sensorimotor system engagement in blink suppression.  It would be an interesting follow-up to investigate whether suppression of normal blinks in TS patients displays the same patterns of activation seen in healthy controls, or reflects impairments in sensorimotor or limbic system control.
Twenty-one adults with TS and 21 healthy controls performed an fMRI study during perception of neutral or angry faces \citep{30346484}. In TS, insula functional connectivity (fc) was increased with preSMA, premotor cortex, primary motor cortex and putamen. Insula fc with globus pallidus and thalamus varied with tic severity, while insula-SMA fc varied with premonitory sensations. These results strengthen the evidence that insula and SMA are involved with premonitory urges and tics.

Pharmacological studies

\citet{Maia_2018} elaborate on their theory of how dopamine may relate to tics in TS. \citet{30072700} provide a meta-analysis of PET and SPECT studies in TS measuring the dopamine transporter (DAT) or D2-like dopamine receptors; neither showed conclusive differences in patients, but sample sizes and methodological limitations may explain the negative results. 

Clinical and neuropsychological studies

The potential role that autoimmunity may play in TS pathology has long been controversial.  A large-scale population study from a Swedish birth cohort assessed the risk factors of 40 different autoimmune diseases in individuals with TS/CTD and/or OCD, as well as family members with varying degrees of relatedness.  TS/CTD was associated with  a 36% increase in likelihood of having any autoimmune disease, compared with matched population controls.  Additionally, the mothers of subjects diagnosed TS/CTD were 40% more likely to have an autoimmune disease; full siblings of individuals with TS/CTD carried a 17% increase in risk.  The authors note that it is undetermined if these numbers support the hypothesized immunological component of TS/CTD, or instead reflect a selection bias for those already receiving medical care \citep{29133949}.