P 3 Mental rotation performance in patients with focal dystonia is associated with their cognitive state

Abstract

Introduction: Mental rotation (MR) of body parts is based on the imagination of actual movements. It is assumed to require activation of brain areas responsible for planning and execution of movements. From previous studies with partly contradictory results, it is still unclear whether patients (pts) with idiopathic focal dystonia have an impairment of MR of body parts. We investigated MR of body parts and non-corporal objects in pts with cervical dystonia (CD) and blepharospasm (BS) and assessed potential confounders of MR performance like cognitive deficits. Patients and Methods: 23 pts with CD and 23 healthy subjects as well as 21 pts with BS and 19 pts with hemifacial spasm (HS) were compared. Matched groups did not differ significantly regarding gender distribution, age, or duration of schooling. Besides handedness, dexterity and general reaction time, cognitive status was assessed using the Montreal Cognitive Assessment (MoCA). Severity of diseases was evaluated by using the Toronto Western Spasmodic Torticollis Rating Scale, Blepharospasm severity scale, Blepharospasm disability index and Jancovic rating scale. In the MR test, photographs of body parts (head, hand, or foot) and other objects such as cars were presented on a screen. Images of the head had a black mark on either the right or left eye, the car had a black mark on either the right or left headlight. The images were presented at six different angles rotated around their own axis. Subjects were asked to select by keystroke whether the right or left hand/foot/headlight was marked. Both speed and correctness of responses were evaluated. For statistical analysis, mixed ANOVA and Spearman-Rho correlation coefficient were applied. Results: In the MR test, pts with CD showed a significantly longer reaction time (RT) compared to healthy controls for both body parts and non-corporal objects (p=0.003, p=0.027). There was no significant difference concerning accuracy except for cars (p=0.048). Furthermore, pts with CD achieved a significantly lower score in the MoCA test compared to controls (p<0.001). Negative correlations were found between MoCA results and RTs in the MR test for all items (hand: r=-0.434, p<0.001, foot: r=-0.419, p<0.001, head: r=-0.363, p=0.001, cars: r=-0.425, p<0.001), whereas there was no correlation between severity of diseases and RTs. No significant differences were observed between pts with B and HS. Conclusion: In our study, prolonged RTs in pts with CD in the MR task are not limited to images of body parts. Rather, we found a significant association of MR performance with cognitive fitness. However, it remains unclear whether increased RTs in pts result from cognitive deficits or from dystonia itself. The former would be supported by the lack of difference in the MR task between BS and HS, whose MoCA results did not differ. Future studies should investigate MR performance in dystonia pts and subjects with comparable cognitive state.