The published literature on the prevalence of pregnancy risk markers in patients with Tourette Syndrome (TS) was reviewed. PubMed was searched for papers describing studies of pregnancy risk markers in TS. All years and languages were searched, and the reference sections of each paper were also reviewed for additional citations. We identified 20 studies reporting on pregnancy risk markers in 1588 subjects with TS. Six studies used comparison populations and two utilized twins for comparisons. Three risk markers (decreased birth weight, father’s age, and number of prior terminations of pregnancy) were identified as possible risk markers for TS. To date, no pregnancy risk marker has been demonstrated to increase risk for development of TS, to increase syndromal severity, rates of comorbidity, or to increase duration of TS.
Developmental disabilities affect millions of people and have highly variable ages of onset, severity, course, response to treatment and outcomes. The public health implications of these disorders are best appreciated by their prevalence, severity and duration. Tourette Syndrome (TS) is a multiple motor and vocal tic disorder, has a typical onset around five years of age, and a peak in symptom severity between nine and eleven years of age, with a gradually improving course for most affected persons [1,2]. Large multicenter studies of TS have demonstrated that comorbid disorders are common and are crucial in determining the severity of TS over time [
The outcomes from longitudinal population based studies of TS suggest a course of gradual improvement for 75% of people and a lifelong course of significant impairment for 15% - 20% of people and severe impairing outcomes for 2% - 5% of people with TS [1,4]. Currently the treatment options for TS and the comorbid disorders that often contribute to the syndromal severity of the disorder are only modestly successful, costly, and have significant rates of side effects, some of which are severe. Access to physicians or management teams with expertise in TS is quite limited especially in the developing world. Thus, the identification of preventable risk factors provides for a potential mechanism for elucidation of the pathophysiology of this disorder. In this paper the term risk marker is used to denote an association with risk in the absence of evidence of a causal association.
A search strategy was developed and conducted by an expert reference librarian with guidance from the authors. The strategy was designed to locate potentially relevant articles regarding perinatal risk factors potentially associated with TS. The search was conducted through the following electronic databases and search engines: PubMed, Scopus, Cochrane Database of Systematic Reviews, Quertle, and Google Scholar. The following key words and subject headings were utilized in the search: tics, Tourette syndrome, Tourette disorder, Gilles de la Tourette Syndrome, chronic tic disorder, transient tic disorder, pregnancy, prenatal, risk factor, risk marker and fetus, foetal, prenatal exposure delayed effects.
The search, which was completed in June 2010, placed no limits on language or publication date. All non-human data was restricted from this review. Hand-searching article reference lists, textbooks and journal issues located additional relevant publications.
Inclusion criteria: The abstracts of articles were reviewed to determine eligibility and relevancy. Papers that identified a prenatal factor and TS were included in the review. We were especially interested in papers that included multiple prenatal risk factors in subjects with TS. We also reviewed the methods section of the full article before excluding any paper.
Exclusion criteria: Papers that did not contain data on prenatal risk factors in subjects with TS were excluded. Data from animal research was excluded from this review.
When examining data from the selected articles, we relied on the original authors’ work to determine if a risk factor was of significance or not. If a risk factor (such as father’s age) met the original test of significance, we then considered it to be a significant risk factor for that article.
It is important to consider the variation in diagnosis and subject ascertainment when comparing the results from reviews of published studies with differing designs. Comparisons across multiple study designs are also very difficult. In this review we found that three primary designs were utilized (group comparisons, case-control studies and case reports). In this study the precise method of measurement or definition of each of the study risk factors likely differs considerably. Thus, we did not pool results from these studies to estimate effect size or risk ratios.