Objective: To evaluate whether perceptual encoding of body motion in cervical dystonia (CD) is associated with co-existing tremor.

Background: Patients with focal CD or hand dystonia exhibit greater absolute timing error, than healthy subjects (HS) when predicting the temporal outcome of a human body movement. This ability is impaired in HS by inhibitory modulation of the cerebellar hemisphere, suggesting the implication of a cerebellum-based internal feed-forward mechanism. Tremor in CD is associated with defective conditioning of the eyeblink reflex or motor adaptation, forms of motor learning that rely on cerebellar processing.

Method: We enrolled 15 treatment-free patients with focal CD, aged 56.2±13.9 years (7 with tremor and 8 without) and 15 age-matched HS. Our experimental paradigm required the visual perception on a computer screen of two videos, one showing a right hand writing a sentence (target task) and another showing a ball reaching a target (control task). After 6, 9 or 12 seconds from the onset, videos were darkened. Subjects indicated when the perceived movement reached its end using a keyboard. The ability to predict the temporal outcome of motion was assessed by the absolute timing error ([(Reproduced Interval–Dark Interval)/Dark Interval]*100) and was analysed with a repeated measures-ANOVA with the factors GROUP (CD with and without tremor and HS), TASK, and DARK INTERVAL.

Results: We detected a trend for a significant effect of the GROUP*TASK interaction term (F2,27=3.23; p=0.055). Post hoc analyses showed greater absolute timing error at all dark intervals on the target compared to the control task only in CD patients with tremor (p= 0.024): in the target task, CD patients with tremor were less accurate than HS (p=0.003), in the absence of any significant difference between CD patients without tremor and HS (p= 0.23), and with a trend towards greater absolute timing error in CD patients with tremor compared to CD patients without tremor (p=0.07).

Conclusion: Our finding represents additional evidence supporting an association between tremor in idiopathic dystonia and cerebellum-dependent sensorimotor control. The characteristics of our temporal prediction task are also in keeping with the recent observation of dysfunctional visual perception of natural motion in dystonia, a network-based domain influenced by cerebellar connectivity.

« Back to 2019 International Congress

MDS Abstracts - https://www.mdsabstracts.org/abstract/defective-human-motion-perception-in-cervical-dystonia-correlates-with-coexisting-tremor/