Clinical rationale for the study: Gilles de la Tourette syndrome (GTS) is a childhood onset disorder characterised by motor and vocal tics. Different types of motor tics may occur in GTS, including dystonic tics (DTs). Although DTs have been recognised as part of GTS symptomatology, little is known about their risk factors or about how often and at what age they appear in affected individuals.
Aim of the study: The aim of our study was to investigate lifetime prevalence and clinical correlations of DTs in a Polish cohort of GTS patients.
Material and methods: We performed a prospective, one-registration study in a cohort of 207 consecutive ambulatory patients (mean age: 16.5 ± 9.4 years, 131 children, 162 males) with GTS. Duration of GTS was 9.0 ± 8.0 years (range: 1-39 years). DTs were diagnosed during the interview. DTs were defined as slower and lasting longer than typical clonic tics, abnormal dystonia-like movements that led to a sustained, but not fixed, posture.
Results: DTs occurred at some point in the lifetime of 73.9% (n = 153) of patients. The prevalence of DTs in adults and children was almost the same (p = 0.963). Age at onset of DTs was 9.9 ± 5.2 years with the most frequent onset in children (7-11 years, 74.4%, n = 64), followed by adolescence (12-18 years; 17.4%, n = 15) and adulthood (≥ 18 years, 8.1%, n = 7). DTs occurred 3.7 ± 4.2 years after tic onset. On average, patients suffered from 1.8 ± 1.7 types of DTs. The most frequent manifestations of DTs were: eyes (tightening resembling blepharospasm 84.3%, n = 129 and oculogyric crisis 45.8%, n = 70), trunk (dystonic postures 59.5%, n = 91), jaw (bruxism 34.6%, n = 53), neck (30.7%, n = 47), upper limb (26.1%, n = 40), and foot (20.9%, n = 32). Multivariate logistic regression analysis showed significant associations of DTs with the total number of simple, and the total number of complex, tics.
Conclusions and clinical implications: DTs are early and frequent symptoms of GTS. They tend to localise in the facial area. DTs occur more frequently in individuals with a higher number of tics and probably add to the global impairment caused by tics.
Keywords: Gilles de la Tourette syndrome; complex tics; dystonia; dystonic tics; simple tics.