ABSTRACT
Both the clinical care of patients with Tourette’s syndrome (TS) and research efforts directed toward the disorder demand the availability of specific, reliable, and valid methods for measuring the severity of tics. In the clinical setting, rating instruments are useful to monitor the course of symptoms and to gauge response to therapeutic interventions. In the research arena, the need for accurate tic ratings is perhaps most obvious for the assessment of novel therapies, such as drug trials. Rating instruments, however, are also crucial for a variety of other investigative avenues. The search for specific and sensitive biological markers for TS requires correlation with disease severity. In family genetic studies, measurement of tic severity may prove useful in identifying subjects who represent nongenetic phenocopies (and might express milder symptoms) and those expressing different genotypes. For example, we may be able to differentiate subjects who are heterozygous or homozygous for the TS genetic trait based on symptom severity (1). In addition, while tics have been observed quite commonly in the general childhood population, at present it remains unclear what proportion carry the TS genetic trait. The measurement of tic severity in epidemiological studies of ticsmay be helpful in clarifying this issue. Accurate characterization of the natural history of TS, including both short-term waxing and waning and long-term course, requires precise measures of severity.
