Contrasting features between Tourette syndrome and secondary tic disorders.

Tics are rapid, recurrent, non-rhythmic movements or emitted sounds. Tics are the hallmark of Tourette syndrome (TS); however, a number of other disorders may be associated with tics, so-called secondary tic disorders (STD). We assessed clinical history and performed blinded evaluations of video-recordings from patients with TS and STD in order to identify features that may differentiate tics associated with TS vs STD. There were 156 patients with TS and 38 with STD, 21 of whom had functional (psychogenic) tics. Patients with TS were more frequently male and had a younger age at onset. Tics in TS tend to involve muscles in the cranial-cervical area more often and have greater severity and complexity than those in patients with STD. Similar findings were observed when contrasting patients with TS with patients with functional tics only. Simple phonic tics showed the greatest diagnostic accuracy for TS, compared with STD, but marked overlap in the types of tics and comorbidities was observed between patients with TS and STD. Patients with TS were more likely males, had a younger age at onset, phonic tics and motor tics affecting predominantly the head and neck area, and had a greater complexity and severity of tics than those with STD. When these features are absent a consideration should be given to the possibility of a tic disorder other than TS.