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Is Persistent Motor or Vocal Tic Disorder a Milder Form of Tourette Syndrome?
Karla Claudio-Campos1,2, Daniel Stevens3, Sang-Wahn Koo2
1Department of Pharmacotherapy and Translational Research, University of Florida College of Pharmacy, Gainesville, Florida, USA.
Background:
Persistent motor or vocal tic disorder (PMVT) has been hypothesized to be a forme fruste of Tourette syndrome (TS). Although the primary diagnostic criterion for PMVT (presence of motor or vocal tics, but not both) is clear, less is known about its clinical presentation.
Objective:
The goals of this study were to compare the prevalence and number of comorbid psychiatric disorders, tic severity, age at tic onset, and family history for TS and PMVT.
Methods:
We analyzed data from two independent cohorts using generalized linear equations and confirmed our findings using meta-analyses, incorporating data from previously published literature.
Results:
Rates of obsessive-compulsive disorder (OCD) and attention deficit hyperactivity disorder (ADHD) were lower in PMVT than in TS in all analyses. Other psychiatric comorbidities occurred with similar frequencies in PMVT and TS in both cohorts, although meta-analyses suggested lower rates of most psychiatric disorders in PMVT compared with TS. ADHD and OCD increased the odds of comorbid mood, anxiety, substance use, and disruptive behaviors, and accounted for observed differences between PMVT and TS. Age of tic onset was approximately 2 years later, and tic severity was lower in PMVT than in TS. First-degree relatives had elevated rates of TS, PMVT, OCD, and ADHD compared with population prevalences, with rates of TS equal to or greater than PMVT rates.
Conclusions:
Our findings support the hypothesis that PMVT and TS occur along a clinical spectrum in which TS is a more severe and PMVT a less severe manifestation of a continuous neurodevelopmental tic spectrum disorder. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.
Insights
Persistent motor or vocal tic disorder (PMVT) is a less severe form of Tourette syndrome (TS). This study found PMVT has fewer comorbidities and milder symptoms than TS, supporting a clinical spectrum.
Area of Science:
- Neuroscience
- Psychiatry
- Genetics
Background:
- Persistent motor or vocal tic disorder (PMVT) is considered a milder form of Tourette syndrome (TS).
- Diagnostic criteria for PMVT are established, but its clinical presentation requires further elucidation.
- Understanding PMVT's relationship to TS is crucial for neurodevelopmental tic disorder research.
Purpose of the Study:
- To compare the prevalence of psychiatric comorbidities, tic severity, age of onset, and family history between PMVT and TS.
- To investigate the role of attention deficit hyperactivity disorder (ADHD) and obsessive-compulsive disorder (OCD) in observed differences.
- To determine if PMVT represents a distinct entity or a spectrum within Tourette syndrome.
Main Methods:
- Analysis of data from two independent cohorts.
- Application of generalized linear equations for statistical analysis.
- Meta-analyses incorporating existing literature to confirm findings.
Main Results:
- Lower rates of OCD and ADHD were observed in PMVT compared to TS.
- While some comorbidities were similar, meta-analyses indicated fewer psychiatric disorders overall in PMVT.
- Later age of tic onset and reduced tic severity were noted in PMVT.
- Elevated rates of TS, PMVT, OCD, and ADHD were found in first-degree relatives.
Conclusions:
- PMVT and TS exist on a clinical spectrum, with TS being a more severe manifestation.
- PMVT represents a less severe form of a continuous neurodevelopmental tic spectrum disorder.
- ADHD and OCD significantly influence comorbidity patterns and differentiate PMVT from TS.
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