Tourette syndrome research highlights 2015
Cheryl A. Richards, Ph.D. (1,2),* Kevin J. Black, M.D. (1,3-5) (ORCiD)
Departments of (1) Psychiatry, (2) Medicine, (3) Neurology, (4) Radiology, and (5) Neuroscience, Washington University School of Medicine, St. Louis, Missouri, USA
* Address correspondence to Dr. Richards at Campus Box 8134, 660 S. Euclid Ave., St. Louis, Missouri, USA or RichardsC@WUSTL.edu.
NOTE: This is an unreviewed preprint version of an article whose final version appears at F1000Research 5:1493, 2016 (doi: 10.12688/f1000research.8769.1).
Copyright © 2015-2016, the authors
We present selected highlights from research that appeared during 2015 on Tourette syndrome and other tic disorders. Topics include phenomenology, comorbidities, developmental course, genetics, animal models, neuroimaging, electrophysiology, pharmacology, and treatment. We briefly summarize articles whose results we believe may lead to new treatments, additional research or modifications in current models of TS.
This article is the second in the TS Research Highlights series (Richards and Black, 2015). These articles are meant to disseminate recent scientific progress on Gilles de la Tourette Syndrome (TS). During each year, the article will be a work in progress, maintained as a web page on the Authorea online authoring platform (the working draft for 2016 appears here). After the calendar year ends, the article is finalized and submitted as the annual update for the Tics channel on F1000Research (Black, 2014).
We searched PubMed on 22 Jan 2016 using the search strategy: ("Tic Disorders"[MeSH] OR Tourette NOT Tourette[AU]) AND 2015[PDAT]. This search returned 202 citations and includes articles appearing online in 2015 but not officially published by year end (from journals that still focus on the paper user interface). We also reviewed F1000Prime recommendations and presentations of interest at selected medical conferences. Articles were chosen based on a purely subjective assessment of interest, guided by our judgment of possible future impact on the field. Some sections conclude with short tables listing additional articles.
Since tic suppression is part of the treatment protocol for the Comprehensive Behavioral Intervention for Tics (CBIT) and for Exposure and Response Prevention, there has been increased interest in investigating the characteristics of tic suppression and the factors that affect it. A study of 26 TS adolescents compared free ticcing with a tic suppression condition (Ganos et al., 2015). During the free ticcing condition, tic distribution across body locations was consistent with the view that most tics occur at the level of the shoulders and above: eye tics were the most frequent, followed by facial/cervical tics, and those involving the arms and legs. Tics involving the trunk were the least common. During the tic suppression condition, eye tics increased in 10 subjects, as did hand tics in 3 subjects. Tic suppression was most successful for tics in body locations generally associated with fewer tics, such as the legs and trunk. The authors suggest that tic suppression involves specific, rather than global, inhibition since some types of tics are easier to suppress than others. Historically, other categories have been used to classify tics, such as simple vs. complex tics and motor vs. phonic tics. The results of this study suggest that future research may benefit from including body location in tic analyses.
By definition, children with Tourette syndrome (TS) have had tics for over a year. They can often suppress their tics briefly and they do so more effectively when rewarded for successful suppression. It has not been known whether the ability to suppress tics develops only with practice over the years of having tics or whether the ability to suppress tics is present when tics initially occur. Greene and colleagues addressed this question in children whose tics had developed within the past few months (Greene et al., 2015). When children received tokens with monetary value for tic-free intervals, they had significantly more of these intervals compared to a baseline, unrewarded condition. T