Objective: Examine functional magnetic resonance imaging (fMRI) activity during hand and foot force production tasks in Parkinson’s disease (PD).

Background: Previous MRI studies in PD focused primarily on identifying the neural correlates of upper extremity dysfunction, a key manifestation of the disease. Although PD progresses to affect lower extremities, there is still a limited understanding of the brain circuitry underlying lower limb symptoms in PD in part due to excessive head motion during leg movements in a supine position, affecting the fMRI signal. Moreover, previous studies examined brain activity related to isolated limb movements. Here, we investigate, for the first time, brain circuity underlying the coordination of hand/foot in a PD cohort.

Method: Study participants included 11 PD and 14 controls. All performed two visually cued isometric force production tasks at 15% of the maximum voluntary contraction: a precision grip task and an ankle dorsiflexion task. PDs were tested after overnight withdrawal from their antiparkinsonian medication and on the more affected side. Motor symptoms were assessed with MDS-UPDRS-III.

Results: Head motion for the two tasks did not differ between groups (p-values > 0.400). Results from the hand voxel-wise analysis confirm previous findings in PD, with reduced activity compared to controls across the basal ganglia, the cortical motor areas and hand territory within the cerebellum. By contrast, the ankle dorsiflexion task revealed reduced activity in PD compared to controls in the basal ganglia (contralateral putamen, GPi), contralateral M1/S, cerebellar vermis I-IV and ipsilateral dorsal dentate nucleus. Percent signal change in vermis I-IV was negatively correlated in PD with total MDS-UPDRS-III (r=-0.759, p=0.007) and the axial subscore (r=-0.615, p=0.044). A trend towards significance was detected for the correlation with the posture and gait subscore (p=0.054).

Conclusion: Results suggest extensive functional abnormalities during both tasks within the basal ganglia- and cerebellar-cortical loops. Moreover, the correlation analyses suggest that the cerebellum may be an important component of the pathophysiology of the disease and its hypoactivity during a lower limb task may explain balance and gait symptoms in PD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/altered-functional-activity-of-the-motor-system-related-to-ankle-and-hand-movements-in-parkinsons-disease-insights-from-functional-mri/