Dystonic motor and phonic tics in Tourette syndrome

Dystonic tics differ from clonic tics by their slower and more sustained nature. Dystonic tics are often present in patients with Tourette syndrome (TS) and other tic-disorders. However, their phenomenology and impact on overall impairment have not been extensively studied.

We assessed clinical history and tic duration in video-recordings from patients with TS evaluated at our movement disorders clinic. Dystonic tics were defined as those lasting ≥ 1000 ms (ms).

Of the total of 201 patients with TS, there were 156 with video-recordings suitable for tic duration analysis, of their tics, 57 (36.5%) of whom had dystonic motor tics, including 9 (5.7%) with dystonic phonic tics. Dystonic motor tics had a duration range between 1033 and 15,000 ms and dystonic phonic tics between 1132 and 17,766 ms. Patients with dystonic tics were older 24.4 vs. 16.5 years (P = 0.005) and had an older age at onset 12.9 vs. 7.2 years (P < 0.001), than patients without dystonic tics. The bivariate analysis showed an association between the presence of dystonic tics, greater tic severity and wider body distribution. The multivariate regression analysis showed a statistical association with older age at evaluation (P = 0.001), greater tic severity on video-recordings (P = 0.001) and co-occurrence with complex motor tics (P = 0.020). The presence of dystonic tics increased the risk for being considered for deep brain stimulation therapy, odds ratio: 15.7 (P = 0.002).

Dystonic tics, observed in about a third of patients with TS, are associated with increased severity of TS.