Unlikely trigger
During the follow-up period, 43.1% (n = 308) of participants experienced tic exacerbations. Of these, 218 participants experienced one exacerbation, while 90 participants experienced two, three, or four exacerbations.
The researchers did not find a significant association between GAS exposure status and tic exacerbation.
Participants who did develop a GAS-associated exacerbation (n = 49) were younger at study exit (9.63 vs. 11.4 years, P < .0001) and were more likely to be male (46/49 vs. 210/259, Fisher’s = .035), compared with participants who developed a non-GAS-associated tic exacerbation (n = 259).
Additional analyses were adjusted for sex, age at onset, exposure to psychotropic medications, exposures to antibiotics, geographical regions, and number of visits in the time interval of interest. These analyses continued to yield no significant association between new or ongoing concurrent GAS exposure episodes and tic exacerbation events.
Of the children in the study, 103 had a positive throat swab, indicating a new definite GAS exposure, whereas 46 had a positive throat swab indicating an ongoing definite exposure (n = 149 visits). Of these visits, only 20 corresponded to tic exacerbations.
There was also no association between GAS exposure and OCD symptom severity. However, it was associated with longitudinal changes (between 17% and 21%, depending on GAS exposure definition) in the severity of hyperactivity-impulsivity symptoms in children with ADHD.
“It is known that immune activation may concur with tic severity in youth with CTDs and that psychosocial stress levels may predict short-term future tic severity in these patients,” the authors write.
“Our findings suggest that GAS is unlikely to be the main trigger for immune activation in these patients,” they add.
Brick or cornerstone?
Commenting on the study for this news organization, Margo Thienemann, MD, clinical professor of psychiatry, Stanford (Calif.) University, said that in the clinic population they treat, GAS, other pathogens, and other stresses can “each be associated with PANS symptom exacerbations.”
However, these “would not be likely to cause PANS symptoms exacerbations in the vast majority of individuals, only individuals with genetic backgrounds and immunologic dysfunctions creating susceptibility,” said Dr. Thienemann, who also directs the Pediatric Acute-Onset Neuropsychiatric Syndrome (PANS) Clinic at Stanford Children’s Health. She was not involved with the study.
In an accompanying editorial, Andrea Cavanna, MD, PhD, honorary reader in neuropsychiatry, Birmingham (England) Medical School and Keith Coffman, MD, director, Tourette Syndrome Center of Excellence, Children’s Mercy Hospital, Kansas City, Mo., suggest that perhaps the “interaction of psychosocial stress and GAS infections contributes more to tic exacerbation than psychosocial stress alone.”
“Time will tell whether this study stands as another brick – a cornerstone? – in the wall that separates streptococcus from tics,” they write.
The study was supported by the European Union’s Seventh Framework Program. Dr. Martino has received honoraria for lecturing from the Movement Disorders Society, Tourette Syndrome Association of America, and Dystonia Medical Research Foundation Canada; research funding support from Dystonia Medical Research Foundation Canada, the University of Calgary (Alta.), the Michael P. Smith Family, the Owerko Foundation, Ipsen Corporate, the Parkinson Association of Alberta, and the Canadian Institutes for Health Research; and royalties from Springer-Verlag. The other authors’ disclosures are listed in the original article. Dr. Cavanna, Dr. Coffman, and Dr. Thienemann have disclosed no relevant financial relationships.
A version of this article first appeared on Medscape.com.