The Spectrum of Tourette Syndrome and Tic Disorders: A Consensus by Scientific Advisors of the Tourette Association of America
Andrea E. Cavanna, M.D., Ph.D.; Keith A. Coffman, M.D.; Heather Cowley, Ph.D.; Stanley Fahn, M.D.; Martin E. Franklin, Ph.D., Donald L. Gilbert, M.D., M.S.; Tamara G. Hershey, Ph.D; Joseph Jankovic, M.D.; Monica M.P. Jones, M.D.; James F. Leckman, M.D.; Rebecca K. Lehman, M.D.; Carol A. Mathews, M.D.; Irene A.C. Malaty, M.D.; Kevin St.P. McNaught, Ph.D.; Jonathan W. Mink, M.D., Ph.D.; Michael S. Okun, M.D.; Jan A. Rowe, OT, OTR/L; Lawrence D. Scahill, MSN, Ph.D.; Jeremiah M. Scharf, M.D., Ph.D.; Bradley L. Schlaggar, M.D., Ph.D.; Evelyn Stewart, M.D.; John T. Walkup, M.D.; Douglas W. Woods, Ph.D.*
- Tourette syndrome (TS) belongs to a spectrum of neurodevelopmental conditions referred to as Tic Disorders.
- TS and other Tic Disorders are not rare. Tics occur in as many as 1 in 5 school-aged children. Some occurrences may be transient, while others will persist into adolescence and adulthood.
- The combined prevalence of TS and other Tic Disorders is estimated to be over 10 cases per 1,000 (1%, 1:100), suggesting that over ½ million children have a Tic Disorder in the US.
- The best estimate for the prevalence of TS is 6 cases per 1,000 (0.6%, 1:160) children, which means that approximately 300,000 children have the condition in the US (based on 2010 Census data).
- There are currently no reliable prevalence estimates of TS and other Tic Disorders in adults, but are expected to be substantially less than in children as tics often decline with aging.
- Further research is needed to provide better estimates of the prevalence of TS and other Tic Disorders across all age groups.
The Occurrence of TS and other Tic Disorders
Tourette syndrome (TS) is a hereditary neurodevelopmental disorder that affects children, adolescents and adults. The condition is characterized by sudden, uncontrollable movements and/or sounds called tics.
TS is a member of a spectrum of similar conditions collectively called Tic Disorders. This group of conditions also includes Chronic Motor or Vocal Tic Disorders (CMVTD) which share many features of and may be misdiagnosed as TS. They differ, however, on the basis that a diagnosis of TS requires the presence of both motor and phonic tics for at least 1 year, while the presence of either motor or phonic tics (not both) for more than 1 year is required for a diagnosis of CMVTD. Individuals with tics present for less than 1 year are given a diagnosis of Provisional Tic Disorder (PTD). In all of these conditions, the diagnosis is only valid if tic onset occurs before the age 18 years and if the tics are not due to an easily identifiable cause such as a medical problem or drug use. Importantly, the spectrum of Tic Disorders is not necessarily a continuum in terms of severity as each disorders (e.g. TS) can be more or less severe than the other (e.g. CMVTD) in the Tic Disorders group.
Individuals with Tic Disorders often have co-occurring psychiatric disorders, most commonly Obsessive-Compulsive Disorder (OCD) or Attention Deficit-Hyperactivity Disorder (ADHD). TS is known for its association with coprolalia, which is the utterance of obscene and socially unacceptable words and phrases. However, coprolalia is relatively rare in individuals with TS (1-2 in 10), is not required for diagnosis, and does not persist in many cases.
Tics and associated symptoms in these conditions may range from mild/inconsequential to moderate and severe, and are disabling in some cases. Indeed, many individuals with tic disorders do not need or seek treatment, while others require multiple therapeutic interventions to manage tics and symptoms of co-occurring conditions. Treatment is generally considered when tics are painful, distressing, interfere with social, academic or professional life. When needed, treatment strategies for all Tic Disorders are the same, and may include medication and/or behavioral intervention. Surgical treatments (i.e. deep brain stimulation, DBS) continue to be developed and should only be considered for the most severe, drug-refractory, cases of Tic Disorders.
Tic Disorders are not rare
The causes of TS and other Tic Disorders remain unclear, but genetic and environmental factors appear to play a role in the development of the conditions. These conditions normally appear during early childhood (as early as 4 years old), occur in both sexes (rates are 3-4 times higher in boys compared to girls), affect all races, and are found in all geographic regions where they have been studied. Prevalence estimates of tics, TS and other Tic Disorders vary widely due to differences in study methods. It is clear, however, that these conditions are not “rare” as they occur with rates significantly higher than the 200,000 person threshold under which the prevalence of a condition must remain to be considered a rare disorder according to the US Rare Diseases Act 2002.
Prevalence of TS and other Tic Disorders
Studies have shown that up to 1 in 5 of children (6-17 years old) exhibit tics at some time during their childhood. Population-based and community-based studies have a wide range of prevalence estimates for TS, from 2.6 to 38 cases per 1,000 children. However, most studies completed in the past decade found rates between 3 and 8 per 1,000. The Centers for Disease Control and Prevention (CDC) reported in 2009 their prevalence estimates of TS from a national, telephone-based, survey in which they asked parents if their children had received a diagnosis of of the disorder. The study found that 3 of every 1,000 children have TS, but it is thought that this underestimates the true occurrence of the disorder. Overall, the best average estimate for TS is approximately 6 per 1,000 children. Prevalence estimates of CMVTD also vary, with rates in the range of 3 to 8 (average 6) per 1,000 children. Therefore, the combined average prevalence of TS and CMVTD is estimated to be approximately 12 per 1,000 children. More studies are needed to determine the prevalence of Tic Disorders in adults, but this is expected to be significantly less than in children due to the fact that tic symptoms abate in later adolescence or early adulthood.
The spectrum of TS and Tic Disorders ranges from transient tics to chronic disorders meeting diagnostic criteria of TS or CMVTD. These conditions are not rare, as each occurs with frequencies well over the rare disease threshold. When the occurrence of TS and other chronic Tic Disorders are combined, the aggregated prevalence is over 10 per 1000 (1%, 1:100). The best estimate of the prevalence of TS only is approximately 6 per 1,000 (0.6%, 1:160) children. Therefore, based on 2010 US Census Data, over 500,000 children have a chronic Tic Disorder (TS and CMVTD combined), or over 300,000 children have TS alone, in the US. Further research is needed to provide better estimates of the prevalence of TS and other Tic Disorders across all age groups.
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Andrea E. Cavanna, M.D., Ph.D., University of Birmingham, Birmingham, United Kingdom
Keith A. Coffman, M.D., Children’s Mercy Hospitals & Clinics, Kansas City, MO
Heather Cowley, Ph.D., Tourette Syndrome Association, Inc., New York, NY
Stanley Fahn, M.D., Columbia University, New York, NY
Martin E. Franklin, Ph.D., University of Pennsylvania School of Medicine, Philadelphia, PA
Donald L. Gilbert, M.D., M.S., Cincinnati Children’s Hospital Medical Center, Cincinnati, OH
Tamara G. Hershey, Ph.D., Washington University School of Medicine, St. Louis, MO
Joseph Jankovic, M.D., Parkinson’s Disease Center and Movement Disorders Clinic, Bellaire, TX
Monica M.P. Jones, M.D., Syracuse Pediatrics, Syracuse, NY
James F. Leckman, M.D., Yale Child Study Center, New Haven, CT
Rebecca K. Lehman, M.D., Medical University of South Carolina, Charleston, SC
Carol A. Mathews, M.D., University of California, San Francisco, San Francisco, CA
Irene A.C. Malaty, M.D., UF Centers for Movement Disorders, Gainesville, FL
Jonathan W. Mink, M.D., Ph.D., University of Rochester Medical Center, Rochester, NY
Kevin St.P. McNaught, Ph.D., Tourette Syndrome Association, Inc, New York, NY
Michael S. Okun, M.D., University of Florida, Gainesville, FL
Jan A. Rowe, OT, OTR/L, Children’s of Alabama, Birmingham, AL
Lawrence D. Scahill, MSN, Ph.D., Emory University School of Medicine, Atlanta, GA
Jeremiah M. Scharf, M.D., Ph.D., Massachusetts General Hospital, Boston, MA
Bradley L. Schlaggar, M.D., Ph.D., Washington University School of Medicine, St. Louis, MO
- Evelyn Stewart, M.D., University of British Columbia, Vancouver, Canada
John T. Walkup, M.D., Weill Cornell Medical College & New York Presbyterian Hospital, New York, NY
Doug W. Woods, Ph.D., Texas A&M University, College Station, TX