14 - Tourette's syndrome: what are we really imaging?

Summary

Introduction

This chapter will discuss and integrate the numerous conflicting findings produced by a wide variety of functional imaging studies in Tourette's syndrome (TS) performed by different investigators under different experimental protocols over a large number of years. We hope in our analysis to identify the neural systems that seem to be most strongly implicated in the pathophysiology of this disorder. We also hope in our analysis to enliven the typically static interpretation of brain images by emphasizing the dynamic interplay of pathophysiology and adaptation, not only in the people who have this particular illness but also in the many others who have difficulty controlling a wide array of unwanted impulses. This dynamic interplay of pathophysiology and adaptation presents important difficulties for the interpretation of existing TS functional imaging studies that will affect the design of the next generation of studies in TS and other developmental neuropsychiatric disorders.

Phenomenology

Simple and complex tics

The tics of TS are rapid, purposeless jerks of brief duration that most commonly affect musculature of the face, head, neck, shoulders, and vocal apparatus. They less commonly affect the torso and extremities. These rapid and brief movements are referred to as “simple” motor or phonic tics, and they are the kind of tics most frequently seen in patients with TS. With increasing age, individuals who have TS become particularly adept at the temporary inhibition of their tics, although tics cannot be inhibited indefinitely. Less commonly seen in TS are slower, semi-purposeful movements of longer duration, which are referred to as “complex” tics.