A new study has found that children with chronic tic disorders, mainly Tourette syndrome, do not have tic exacerbations when exposed to group A Streptococcus.
No significant association with tic exacerbations emerged across four definitions of pharyngeal strep exposure with a mean follow-up of 16 months, though a weak link was observed in trend, reported Davide Martino, MD, PhD, of the University of Calgary, and co-authors.
Strep was however significantly associated with longitudinal changes in hyperactivity-impulsivity symptom severity of 17% to 21%.
“The link between Streptococcus and tics in children is still a matter of intense debate,” Martino stated. “We wanted to look at that question, as well as a possible link between strep and behavioral symptoms like obsessive-compulsive disorder and attention deficit hyperactivity disorder.
“While our findings suggest that strep is not likely to be one of the main triggers for making tics worse, more research is needed into other possible explanations. For example, the social stress of having this disorder could be implicated in making tics worse more than infections. It’s also possible another pathogen might be triggering an immune response associated with tic worsening.”
In an invited editorial, Andrea Cavanna, MD, PhD, of the University of Birmingham, and Keith Coffman, MD, of Children’s Mercy Hospital in Kansas City, observed that group A Streptococcus had been posited as a potential environmental factor in tic disorders for the past two decades.
The editorialists noted that, on the basis of isolated clinical observations, tic disorders should be included as a collateral feature in conditions which are known as pediatric autoimmune neuropsychiatric disorders associated with Streptococcus (PANDAS) infections. However, the results of longitudinal clinical studies were inconclusive, with a case control study even arguing against the association.
Drawing data from the EMTICS study, recruiting children with chronic tic disorders from 2013 to 2016, one arm of the study prospectively examined associations between new group A Streptococcus throat exposures and tic exacerbations, obsessive-compulsive disorder (OCD), and attention deficit hyperactivity disorder (ADHD) symptoms.
Four definitions of strep exposure were used: new definite (newly positive throat swab regardless of serological results), new possible (elevated anti-streptolysin O [ASOT] or anti-DNAseB [ADB] titers with negative or no throat swab), ongoing definite, and ongoing possible.
Initially, 59 children had a positive throat swab; as the study progressed, 103 children had new definite strep exposure. During follow-up, 308 children (43%) had tic exacerbations. The proportion of exacerbations temporally associated with strep exposure ranged from 5.5% to 12.9%, depending on exposure definition. No association between OCD symptoms and strep exposure was seen.
“Our study of the largest prospective cohort of youth with chronic tic disorders ever documented to date provides evidence against a temporal association between group A Streptococcus exposure and clinically relevant tic exacerbations,” the researchers wrote.
“This result indicates that specific diagnostic work-up or active management of group A Streptococcus infections in the context of worsening of tic severity in patients with chronic tic disorders is not warranted,” the researchers added.
The researchers noted that limitations included the data being collected from specialist centres in different countries, and that some cases of strep may have been missed.
Source: MedPage Today
Journal information (article): Martino D, et al “Association of Group A Streptococcus Exposure and Exacerbations of Chronic Tic Disorders: A Multinational Prospective Cohort Study” Neurology 2021; DOI: 10.1212/WNL.0000000000011610.
Journal information (editorial): Cavanna A, Coffman K “Streptococcus and Tics: Another Brick in the Wall?” Neurology 2021. DOI: 10.1212/WNL.0000000000011608.
