Tourette syndrome and consciousness of action

Background: Tourette syndrome (TS) is a neuropsychiatric disorder characterized by the chronic presence of multiple motor tics and at least one vocal/phonic tic since childhood. Tics typically change and vary in both intensity and severity over time, with remission and exacerbation common. In the vast majority of patients, tic expression is characteristically accompanied by discomforting bodily sensations, known as sensory phenomena or premonitory urges. Methods: We reviewed the existing literature on premonitory urges associated with the sense of voluntariness of action in TS. Results: Although the wish to move is perceived by the patient as involuntary, the decision to release the tic is often perceived by the patient as a voluntary capitulation to the subjective urge. Most patients with TS can exert a degree of control over the urge and constantly try to inhibit the movement. Based on these features, it has been suggested that tics performed in response to an urge to move should be classified as 'unvoluntary', as opposed to voluntary or involuntary acts. However, recent experimental data suggest that the brain areas involved in the generation of the wish to act show considerable overlap between healthy subjects and patients with TS. Discussion: The simultaneous presence of both voluntary and involuntary aspects in the expression of tic symptoms by patients with TS is consistent with the hypothesis that tics can have the same neurophysiologic substrate as voluntary acts, even though they are misperceived as being involuntary. This reinforces the view of TS as a hyperkinetic movement disorder primarily affecting the conscious experience of action.