Tourette Syndrome: Clinical Features and Pathophysiology

Abstract

Tourette syndrome (TS) is a neuropsychiatric disorder with the onset in childhood. TS is a form of tic disorders, and characterized by the motor and vocal tics, and comorbidities such as attention deficit hyperkinetic and obsessive compulsive disorders. These symptoms appear age dependently, showing a wax and wane course, and subside or abolish by the late teens. Pathophysiology of TS involves the dysfunction of both motor and non-motor basal ganglia-thalamo-cortical circuitries. The nigrostriatal dopamine (DA) system takes the exponential decrement at the striatum. In TS, this decrement is accelerated in association with DA-D2 receptor super-sensitivity, which disinhibits the descending and ascending output pathways of the basal ganglia. Disinhibited motor basal ganglia-thalamo-cortical circuitries develop the specific tics according to the target sites. Hypofunction of the 5-hydroxytriptophan (5-HT) neurons of the brainstem innervate the striatum involved in non-motor basal ganglia-thalamo-cortical circuitries and cause the obsessive compalsive disorder and other behavioral disorders. The associated DA-D2 receptor supersensitivity is assumed to be a consequence of the developmental abnormalities and not due to denervation supersensitivity. The treatments of TS aim to correct the 5-HT hypofunction by improving the environmental factors and super-sensitized DA receptors medically by a small dose of levodopa and/or aripiprazole.