Objective: The aim of this study was to assess brain activation during voluntary sequential finger tapping in cervical dystonia patients while manipulating task complexity.

Background: Cervical dystonia (CD) is a movement disorder characterized by involuntary muscle contractions leading to abnormal head posture. Despite predominantly focal manifestation, CD is also associated with discrete deficits in praxis and abnormal sensorimotor activation during sequential finger movements.

Method: Participants (15 CD patients, 12 healthy controls) underwent one 3T fMRI session, during which they performed blocks of sequential finger tapping with their right hand according to visual cues. Each tapping epoch (TAP) included 4 repetitions of a 4-item sequence presented once during cue epoch (CUE). One half of the blocks consisted of a repeated simple constant sequence (CON condition), whereas the second consisted of unique pre-randomized sequences (RAN condition).

Results: In both groups, RAN-TAP was associated with increased activation in the premotor and posterior parietal cortices and decreased activation of the default mode network, whereas CON-TAP resulted in increased activation of the basal ganglia. In combined condition RAN+CON-TAP, patients activated more the left parietal operculum and less the bilateral sensorimotor cortex. During CUE, patients activated more the medial frontal cortex and activated less the left frontoparietal network. They also activated more bilateral premotor cortices during RAN-CUE, but not during CON-CUE.

Conclusion: We provide evidence for differences in the cortical representation of simple and complex motor sequential movements between patients with CD and healthy controls, confirming that CD is a system-wide disorder of central motor control and planning.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/abnormal-sensorimotor-processing-in-cervical-dystonia-in-functional-magnetic-resonance-imaging/