Rotational plane-wise analysis of angular movement of neck motor tics in Tourette's syndrome

Motor tics are sudden, rapid, recurrent, non-rhythmic movements. There is a lack of quantitative assessment methods for the motor tics despite severe neck complications. We aimed to provide an improved quantitative method for neck tic assessment in motor tic disorders. We recorded neck motor tics in patients with motor tic disorders and voluntary neck movements in healthy controls. The maximum peak angular velocities and angular accelerations were calculated. Motor tics were assessed in three orthogonal planes (yaw, pitch, and roll) separately, and compared between the patients with motor tic disorders and controls. Correlations between the maximum angular velocities/accelerations and tic counts were also assessed. In the pitch plane, motor tics of the patients showed higher angular velocities/accelerations than voluntary movements of the controls. Angular acceleration in the yaw, and roll planes showed positive correlations with tic count. Some of the observed tics were comparable to the movements experienced in contact sports. Our findings may aid in the identification of populations at a high risk for severe neck complications among motor tic disorder patients.