Gilles de la Tourette's syndrome (
Tourette's syndrome; TS) is an inherited
tic disorder commonly associated with other neurobehavioural conditions such as
attention-deficit hyperactivity disorder (
ADHD) and
obsessive-compulsive disorder (OCD). While the clinical presentation of TS and other features of this disorder have been well characterized, the genetic and neurobiological basis of the disease remains incompletely elucidated. The suggestion of a central role of
dopamine in the aetiology of TS has been made on the basis of experimental studies, evidence from neuroimaging studies and the therapeutic response patients with TS have to agents that antagonize or interfere with putative dopaminergic pathways.
Tetrabenazine is such an agent; it depletes presynaptic
dopamine and
serotonin stores and blocks postsynaptic
dopamine receptors. In clinical studies,
tetrabenazine has been found to be effective in a wide range of
hyperkinetic movement disorders, including small numbers (<50) of patients with TS in some studies. Results of a retrospective chart review enrolling only patients with TS (n = 77; mean age approximately 15 years) showed that 2 years' treatment with
tetrabenazine resulted in an improvement in functioning and TS-related symptoms in over 80% of patients, findings that suggest that treatment with
tetrabenazine may have long-term benefits. The authors' experience with 120 heavily co-medicated patients with TS confirms these findings. Long-term (mean 19 months)
tetrabenazine treatment resulted in a Clinical Global Impressions of Change scale rating of 'improved' in 76% of patients. Such findings are promising and suggest that
tetrabenazine may be suitable as add-on
therapy in patients for whom additional suppression of
tics is required.