Objective: To explore proprioceptive performance in children with Tourette syndrome (TS) using a robot-based task.

Background: Sensory processing in TS may be affected by noisier signals [1], affecting proprioception [2]. While the underlying mechanisms are unclear, some evidence suggests frontostriatal dysfunction may lead to deficits in sensory signal processing and feedback-based corrections of voluntary movement [1].

Method: Sixty-three children diagnosed with TS (mean age 12.4 years; 7.5-18.5) were evaluated using a validated robotic bimanual exoskeleton protocol (Kinarm) in an arm-position-matching task. Participants were instructed to mirror-match the position of a limb to that of the contralateral limb, passively moved by the Kinarm to a test position in the horizontal plane, without relying on visual feedback. Both dominant and non-dominant limbs were tested. The Kinarm measured several kinematic variables related to proprioception [3]. Performance was compared to a database of 155 healthy control children (mean age 13 years; 6.1-19.9), using ANCOVAs with age as a covariate.

Results: Participants with TS showed an increase in variability in hand position (4.0 cm, 95% CI 3.7-4.2) versus controls (3.3, 3.1-3.5). This increased variability remained when the TS group was split into those without comorbid ADHD (4.0, 3.6-4.4; n=30) and those with comorbid ADHD (3.9, 3.5-4.3; n=31), with no differences between the patient groups. Only those with comorbid ADHD differed significantly from controls in mean absolute distance error in x and y (6.2, 5.4-6.9; vs. 5.1, 4.8-5.4). Patients and controls did not differ significantly in variables related to shift in the limb’s perceived position, or to contraction/expansion of perceived position.

Conclusion: In the bimanual arm-position-matching task, children with TS showed greater variability in the upper limb’s perceived position. This appears to be independent of ADHD, as patients with and without ADHD performed similarly in terms of variability. The findings lend support to the hypothesis that TS is associated with noisier sensory signals, given the finding of increased variability but without a warping of proprioception, such as shift or contraction/expansion in perceived position.

References: [1] Ganos et al. (2018). Voluntary inhibitory motor control over involuntary tic movements. Mov Disord, 33(6): 937-46. [2] Lemay et al. (2007). Postural control abnormalities in children with Tourette syndrome. Exp Brain Res, 179(3): 525-30. [3] Dukelow et al. (2010). Quantitative assessment of limb position sense following stroke. Neurorehab Neural Repair, 24(2): 178-87.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/children-with-tourette-syndrome-show-greater-variability-in-an-arm-position-matching-proprioceptive-task/