Gilles de la Tourette's syndrome. A review of clinical and research studies and consideration of future directions for investigation.

Tourette syndrome (TS) is a complex neurobehavioral disorder that has recently become a topic for clinical, genetic, neurochemical, and therapeutic research. Substantial progress has been made defining the clinical features of the disorder, establishing its familial nature, and documenting its response to pharmacotherapeutic intervention. Despite these advances, significant problems remain. The separation between TS and other syndromes is imprecise, and there are no uniformly accepted criteria for measuring response to treatment. Although family studies are promising, no mechanism of genetic transmission has been defined and the number of available revealing kindred for future DNA linkage studies is small. Clinical neurochemical investigations have been hampered by poor design and small subject samples; detailed postmortem neurochemical and pathological studies of brains from patients with TS have not been undertaken thus far. Careful application of newer research technologies combined with appropriately chosen subjects with TS may add to our understanding of the physiologic, anatomic, and genetic factors that contribute to this intriguing disorder. Future postmortem central nervous system studies will be essential.