Tourette's Disorder Scale

The Tourette's Disorder Scale (TODS) is a psychological measure used to assess tics and co-occurring conditions in Tourette syndrome, a disease characterised by simple and complex motor and vocal tics and a wide range of behavioural and emotional symptoms. There are two versions of TODS (TODS-CR and TODS-PR), each being a 15-item scale that helps clinicians evaluate the severity of various symptoms associated with tics, inattention, hyperactivity, obsessions, compulsions, aggression and emotions.

Context
TODS is one of many instruments currently used to measure Tourette syndrome. The Yale Global Tic Severity Scale (YGTSS) is regarded as the most developed instrument of measuring Tourette syndrome and widely accepted as the standard for assessing tics. In a systematic review, panel judgement concluded that TODS, YGTSS, Shapiro TS Severity Scale and Tourette Syndrome Clinical Global Impression are currently the only four instruments that are reliable and comprehensive, with approximately ten other instruments unsuitable for use.

The clinical approach typically targets the most apparent symptoms of a disorder in hopes of assigning the appropriate treatment. Hence, most instruments measuring Tourette syndrome use tic severity as the primary indicator of the disorder’s severity. Tics are often involuntary, repetitive and sudden actions and noises such as eye blinking and rolling, jerking limbs, throat clearing and saying socially unacceptable words, making them easily identifiable to clinicians and family members. TODS differs from other instruments in that it not only measures tic severity, but also measures the behavioural and emotional symptoms that accompany Tourette syndrome. The presence of more than one condition in an individual concurrently is known as comorbidity, which is typical in Tourette syndrome patients. Behavioural and emotional symptoms typically associated with Tourette syndrome include:  Attention Deficit Hyperactivity Disorder (ADHD), Obsessive Compulsive Disorder (OCD), Rage Attacks, Depression, Sleep issues, Migraines and learning disabilities.

Justifying the inclusion of behavioural and emotional symptoms in instruments measuring Tourette syndrome, experts suggest that behavioural and emotional symptoms could be more disruptive and damaging to one’s quality of life than tics. Furthermore, research suggests that while tic symptoms tend to decrease in severity over time (particularly past one’s adolescent years), comorbidities worsen. Rizzo and colleagues found that over 42% of Tourette syndrome patients in their study had developed OCD alongside their initial Tourette syndrome diagnosis.

Development
In a paper by Shytle and colleagues, a survey was sent to parents on a Tourette Syndrome email list, asking them to rate the frequency and relative significance of 32 behavioural and emotional symptoms observed in their children. Of 35 respondents, 80% concurred that behavioural and emotional symptoms were more afflicting than tics. This reaffirmed researchers of the relevance of behavioural and emotional symptoms in constructing a Tourette syndrome instrument.

Symptoms discerned as frequently disruptive to Tourette syndrome patients and rated as a “top 10” problem by over 25% of participants in the study (parents and clinicians) were included in the construction of TODS. Two versions of TODs were established, one using parental ratings and the other using clinician ratings.

TODS-PR
Parents subjectively rated symptom severity in accordance with their observations over fixed time periods.

TODS-PR items:


 * Irritable
 * Motor tics
 * Argumentative
 * Sudden mood changes
 * Demands attention
 * Hot temper
 * Vocal tics
 * Obsessions
 * Difficulty paying attention
 * Loud or talkative
 * Restless or “hyper”
 * Compulsions
 * Tense or anxious or nervous
 * Depressed or uninterested in most things
 * Impulsive

TODS-CR
A semi-structured interview was conducted by clinicians with those suffering from Tourette Syndrome and their parents. After using the MINI-KID (child and adolescent version of the MINI International Neuropsychiatric Interview) to determine the presence of Tourette Syndrome and comorbidities, clinicians posed questions to the children. Following, parents were asked to contribute to the responses, until clinicians reached an agreement on the rating of each symptom.

TODS-CR items:


 * Irritable
 * Motor tics
 * Argumentative
 * Sudden mood
 * Demands attention
 * Hot temper
 * Vocal tics
 * Obsessions
 * Loud or talkative
 * Restless, Compulsions
 * Tense or anxious or nervous
 * Depressed or uninterested in most things
 * Impulsive

Validity
Studies suggest that tic factors in TODS and YGTSS are significantly and positively correlated. Both TODS-CR and TODS-PR also demonstrate high internal consistencies. Parents and clinicians typically agreed with each other on symptom ratings. However, for the ADHD factor and TODS total score, clinicians rated the distress to patients’ as significantly greater than parents did. Explanations for this discrepancy mainly highlighted clinicians’ greater level of detachment from the patient’s lives compared to parents, allowing them to be more objective in assessment and attuned to the patients’ distress.

Limitations of TODS
TODS has been criticsed for its lower interrater reliability relative to that of other instruments. In addition, TODS is unable to measure various aspects of tics to the same extent that other instruments do. Only assessing the overall severity of tics, TODS is unable to capture information regarding the frequency, intensity and complexity of the tics, resulting in a lack of precision in symptom measurement. Furthermore, TODS requires over 20 minutes for administration compared to an average of 10 minutes in other instruments, making it a lengthy diagnostic process.

Limitations of instruments measuring Tourette syndrome
Cross-cultural studies have shown that clinical features and symptoms of Tourette disorder such as the age of onset for Tourette syndrome and the location of the first tics are uniform across cultural groups. However, this does not address cross-cultural variance in comorbid conditions that frequently accompany Tourette syndrome. The reliability of TODS, like many other instruments, has been tested with a largely Caucasian sample of patients, resulting in low generalisability of findings. Eapen and colleagues contrasted a sample of Tourette syndrome patients from the United Kingdom and United Arab Emirates, highlighting a divergence of comorbidities (specifically oppositional defiant disorder and conduct disorder) between samples. Researchers attributed these differences to environmental influences that influenced the manifestation of Tourette syndrome in patients, socio-cultural religious differences and varying cultural perceptions of symptom severity.