Circuits to synapses: The pathophysiology of tourette syndrome

Tourette syndrome (TS) is a childhood-onset neuropsychiatrical disorder characterized by chronic motor and vocal tics that are frequently accompanied by coexisting problems such as obsessive-compulsive disorder (OCD) and attention deficit hyperactivity disorder (ADHD). The precise underlying pathophysiological mechanism(s) for tics is unknown. This chapter provides an overview of clinical issues pertaining to tic disorders and discusses the pathobiology of TS. Neuroanatomical and neurophysiological studies suggest an abnormality involving cortico-striatal-thalamo-cortical (CSTC) circuits, but the site of primary dysfunction is controversial. A growing body of evidence indicates that an abnormality in CSTC circuits and their neurotransmitter systems are likely to be associated with tics and coexisting problems in TS. Neurochemically, evidence continues to support involvement of the dopaminergic system, but other neurotransmitters within CSTC circuits may also be involved. Although assigning a role to the immune system in the etiology of TS remains an intriguing hypothesis, convincing evidence supporting an immune-mediated process is not available.