Tourette Syndrome: Update

Abstract

Tourette Syndrome is a disorder characterized by tics. It typically begins in childhood and often improves in adult life. Tics are best described as voluntary movements made automatically so that volition is not ordinarily appreciated. There is frequently an urge, sometimes in the form of a specific sensory feeling (sensory tic), that precedes the tic. Patients say that they make the tic in order to reduce the urge, although shortly after the tic, the urge recurs. The sensory feeling may arise due to defective sensory habituation. Since tics relieve the urge, this can be considered rewarding, and repetition of this behavior may perpetuate the tic as a habit. Tourette Syndrome affects boys more than girls and is associated with attention deficit hyperactivity disorder and obsessive compulsive disorder. Although Tourette Syndrome often appears to be autosomal recessive in inheritance, it has been difficult to find any abnormal genes. There is a loss of inhibition in these patients and recent studies show abnormalities in brain GABA. Certainly there is also an abnormality in dopamine function and dopamine blocking agents are effective therapy. In severe drug-refractory patients, deep brain stimulation can be effective.

Keywords: Dopamine; Habit; Inhibition; Sensory habituation; Tic; Urge.

Figure 1

Event related functional MRI of tics. Statistical parametric maps superimposed on axial (A), coronal (B) and sagittal (C and D) views are shown. The upper row shows significant activations (P < 0.05, corrected for multiple comparisons) of paralimbic areas (ACC and insular region bilaterally) before tic onset; these activations were much less prominent at tic onset (lower row). From Bohlhalter S, Goldfine A, Matteson S et al. Neural correlates of tic generation in Tourette syndrome: an event-related functional MRI study. Brain 2006;129:2029–2037, with permission.

Figure 2

Brain areas with decreased binding of [¹¹C]flumazenil in Tourette syndrome patients versus control subjects: the most significant decreases were seen in the bilateral ventral striatum (VS), bilateral thalamus (Th), right insula (Ins) and bilateral amygdala (Amg). From Lerner A, Bagic A, Simmons JM, et al. Widespread abnormality of the gamma-aminobutyric acid-ergic system in Tourette syndrome. Brain 2012;135:1926–1936, with permission.