The functional neuroimaging of Tourette syndrome and obsessive-compulsive disorder

Abstract

Tourette syndrome (TS) is a developmental neuropsychiatric disorder characterized by the presence of tics and is often associated with other comorbidities. Obsessive-compulsive disorder (OCD) is one of the most common comorbid disorders in TS with the majority of TS patients experiencing significant obsessive-compulsive symptoms (OCS) that often substantially contributes to the disease burden of TS. There are also striking phenomenological similarities between TS and OCD, as they are both characterized by repetitive behaviors that are frequently preceded by sensory phenomena; these similarities, coupled with the high prevalence of OCS in TS, raise questions as to the neural substrates of tics and OCS. There has been considerable research interest into the functional neuroactivity of patients with TS and those with OCD, but there is a paucity of research on comorbid TS + OCD, especially with regards to how it differs from its classical counterparts. This chapter will review the functional neuroimaging research on tics, OCS, sensory phenomena and functional connectivity that has been conducted in TS, OCD, and TS + OCD samples. As well, hypothesized neurobiological models of the above diagnostic groups will be reviewed with a special emphasis as to how the neurobiology of tics differs from OCS, and how TS + OCD may differ from TS and OCD.