Objective: In this study we investigate two neurophysiologic variables testing for central-peripheral and peripheral-central mechanisms of SM integration in a cohort of TSD to evaluate differential aspects of SM integration.

Background: Task-specific dystonia can be defined as loss of motor control for a learned and perfected motor skill and it shares pathophysiologic mechanisms with other forms of dystonia. Abnormalities in sensorimotor (SM) integration involving different tiers of the nervous system can be deemed to be the unifying pathophysiologic mechanism for different forms of dystonia with differential/predominant involvement of different SM integrators/networks resulting in different dystonia phenotypes.

Method: We studied 9 patients with TSD with dominant right upper limb involvement and 13 right-handed age/sex-matched healthy volunteers (HV) and assessed the following clinical neurophysiologic variables; 1. Somatosensory discrimination thresholds; a. Temporal discrimination threshold (TDT), b. Spatial discrimination threshold (SDT) and 2. Cortical-silent period (CSP) using a standardized experimental setup. Data were analyzed for normal distribution and the differences in the neurophysiologic variables between the groups were tested using t-test.

Results: No significant difference in TDT in TSD compared to healthy subjects (p=0.13), with no differences between the dystonic (Dys) and normal limbs (NDys) in TSD (p=0.25). No significant differences in SDT in TSD compared to HV (p=0.56). Significantly prolonged CSP in TSD compared to HV (p=0.0013).

Conclusion: Our findings are suggestive of predominant top-down SM integration abnormalities in TSD resulting in corruption of a learned and perfected motor skill.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/task-specific-dystonia-is-a-predominant-disorder-of-top-down-sensorimotor-integration/