The formal criteria for Tourette Syndrome provided by The Tourette Syndrome Classification Study Group includes:
- the presence of multiple motor and at least one vocal tic (not necessarily concurrently)
- a waxing and waning course with tics evolving in a progressive manner
- the presence of tic symptoms for at least one year
- the onset of symptoms before age 21
- the absence of a precipitating illnesses (e.g., encephalitis, stroke, or degenerative disease) or medication
- the observation of tics by a knowledgeable individual
Coprolalia, one of the most socially distressing symptoms of tic disorders, is not a diagnostic criterion nor is there a requirement for comorbid neurobehavioral problems. Accurate separation of chronic tic disorders from TS is essential for researchers, but has little relevance for outcome or treatment.
Tics have a waxing and waning course and fluctuation of symptoms is expected. In most patients, motor and vocal tics remain mild but require long-term follow up. Although TS was originally proposed to be a lifelong disorder, its course may be quite variable with some patients having a spontaneous remission or marked improvement independent of the use of tic-suppressing medication. In discussions of outcome, we use the "rule of thirds" (1/3 disappear, 1/3 are better, and about 1/3 continue). To date, there are no good prognostic indicators, however, to assist in determining into which group a patient will ultimately fit as he/she gets older.