A task force (The Tourette Syndrome Classification Study Group), organized by the Tourette Syndrome Association, has expanded the DSM-IIIR definitions of Tourette syndrome and is developing a quantitative rating scale for tics to be used by clinicians in practice and in genetic and other research activities. Each of the four basic DSM definitions (Tourette syndrome, chronic tic disorder, transient tic disorder, and non-specified tic disorder) is divided into two categories; “definite,” tics witnessed by a reliable observer, and “historical,” putative tics not reliably witnessed. Additional tic categories have been included: chronic single tic disorder; definite tic disorder-diagnosis deferred (symptoms less than 1 year); and probable Tourette syndrome (some criteria for diagnosis absent). 
COMMENT. A similar classification was proposed by a TSA workshop in a previous report (see Progress in Pediatric Neurology, Chicago, PNB Publishers, 1991; 230-232). 
Most tics are idiopathic but some are symptomatic of head trauma, encephalitis, or other etiologies. Three children with carbamazepine-induced tics are reported from the Departments of Pediatrics and Neurology, University of Michigan Medical Center, Ann Arbor, MI . The temporal association of repetitive blinking, jaw opening or clenching, and tongue movements with the initiation of CBZ treatment for complex partial seizures, and the absence of other etiologies, suggests that CBZ was the likely cause. Additional cases of carbamazepine-related tics and other movement disorders have been reported.
The contingent negative variation (CNV), a slow brain potential which may reflect the level of central dopamine and is a measure of arousal and attention, has been studied in patients with Tourette syndrome . Patients had higher CNV amplitude and more frequent postimperative negative variation than controls, possibly explained by dopaminergic excess. Medication was not a factor.