Causes/Pathophysiology

The genetics of TS is not well understood, and a substantial percentage of the human genome has been excluded. (The human genome is the complete set of genes in the chromosomes of human cells.) However, genetic analysis (genome scanning) of numerous pairs of siblings has shown several areas that may contain genes that, when mutated, may give rise–or increase susceptibility-to TS. There is some evidence that, in some instances, TS may be inherited from both parents (bilineal transmission), with the father typically affected by childhood tics and the mother typically having symptoms of obsessive-compulsive behavior.

The basic underlying defect in TS is unknown. However, many researchers suggest that the disorder results from abnormalities in the activity of certain chemicals in the brain known as neurotransmitters, particularly dopamine within the basal ganglia. This is supported by biochemical brain analysis of patients with TS and the observation that dopamine-blocking agents (dopamine receptor antagonist) suppress tics in some patients. In addition, abnormalities in serotonin activity and other neurotransmitters are thought to play some role in causing symptoms associated with TS.

	Diagnosis