Objective: To evaluate changes in brain potentials related to sensory tricks in cervical dystonia (CD) activity compared to healthy volunteers using EEG

Background: Sensory tricks are a common feature among patients with CD. The presence of sensory tricks supports the theory that dystonia is a disorder of sensorimotor integration. Previous studies suggest that sensory tricks may involve complex physiological mechanisms. Contingent negative variation (CNV) is a slow, negative brain potential occurring between two successive stimuli that are associated with or contingent on each other. CNV can be considered as a sign of ‘sensorimotor association’ in various motor tasks.

Methods: Thirteen CD patients (mean age = 59.4 yrs) and a control group of 13 age-matched healthy volunteers (mean age = 58.8 yrs) participated in the study. EEGs were recorded from 32-channel scalp-surface electrodes. The experimental block consisted of three conditions (moving neck, moving arm, and performing sensory tricks) and each experimental block was repeated three times. Participants were instructed to be ready to perform the task for each condition according to the instructions seen on the screen (S1), and then to perform the task when the second stimulus (S2). Early CNV was defined as the peak amplitude of EEG activity from 1000 ms to 2000 ms after S1, and late CNV was measured as the average EEG activity from 500 ms to 0 ms before S2. Data were analyzed at selected electrodes; FCz, Cz, C3 and P3.

Results: There was significant difference in the late CNV at Cz (p = 0.003) and FCz (p = 0.011) electrodes between patients and controls, while the late CNV at C3 and P3 showed a trend toward statistically-significant difference between groups (C3: p=0.064; P3: p = 0.072). In addition, a significant between-event difference in late CNV amplitude was observed at Cz (p=0.046) with the potential associated with the sensory trick being the largest. However, there was no significant difference in early CNV amplitudes either between groups (p = 0.485) or between events (p = 0.929) at all selected electrodes.

Conclusions: With sensory tricks, the late CNV is significantly higher among CD patients than healthy controls, suggesting that sensory tricks may act on motor preparatory mechanisms in the pre-movement phase, thereby normalizing impaired sensorimotor integration during voluntary movement. Such compensatory mechanism appears to occur within the central rather than parietal area, while the early processing of stimulus does not appear to contribute to efficacy of sensory tricks in CD patients.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/contingent-negative-variation-in-patients-with-cervical-dystonia-related-to-sensory-tricks/