Objective: To investigate the kinematic basis of balance impairment in Cervical Dystonia (CD) and the response to different treatment modalities.

Background: Several studies have demonstrated subclinical abnormalities of gait and balance in CD, suggesting motor network dysfunction extending beyond control of head position. It is unclear how these impairments relate to the motor phenotype and whether they respond to treatments that are effective in CD.

Method: 61 CD subjects and 49 controls completed a balance task while wearing a wireless inertial measurement unit (IMU) sensor recording triaxial linear acceleration () from the trunk. The task consisted of standing on each leg for 10 seconds. The frequency of foot-to-ground touches was counted and combined with the sensor data to calculate the balance stability index (BSI), defined as the ratio of the integral of the composite acceleration vector to the task duration minus foot-to-ground frequency, with lower values indicating greater stability. BSI was compared between CD and controls, and before and after treatment with botulinum toxin (BT) and deep brain stimulation (DBS). Relationship between BSI, clinical severity by Tsui scale, and kinematic metrics of head motion were tested using Spearman’s rank coefficient with Bonferroni correction.

Results: Median BSI when balancing on the right leg was 403.5 (IQR 223.9-600.3) in CD compared to 235.2 (173.2-291.9) in controls (p<0.001). Median left leg BSI was 558.9 (267.8-749.9) in CD compared to 294.9 (195.6-397.0) in controls (p<0.001). Within individuals, left leg BSI was significantly higher than right leg BSI for both CD (p=0.001) and controls (p=0.002). In CD a significant reduction was seen in left leg BSI following both BT (p=0.01) and DBS (p=0.007), while no significant change occurred in right leg BSI. BSI correlated with Tsui scale total score (r0.43, p<0.001) and with kinematic measures of involuntary head movement severity (r0.47, p<0.001) and voluntary head movement smoothness (r-0.4, p=0.001).

Conclusion: This study provides objective kinematic evidence of impaired truncal stability in CD. This impairment correlates with kinematic metrics of head movement and with clinical severity as rated using the Tsui scale. BSI responds to treatment with both BT and DBS. Further research is required to establish whether impaired balance is an independent motor deficit or a secondary consequence of involuntary head movement.

« Back to 2025 International Congress

MDS Abstracts - https://www.mdsabstracts.org/abstract/kinematic-assessment-of-balance-in-cervical-dystonia/