Differences in brain activation between tremor- and nontremor-dominant parkinson disease

Objective: To compare differences in functional brain activity between tremor- and nontremor-dominant subtypes of Parkinson disease (PD) using functional magnetic resonance imaging. Design: In our study, patients with tremor-dominant PD and those with nontremor-dominant PD performed a grip task, and the results obtained were compared using voxelwise analysis. Areas of the brain that were significantly different were then examined using a region-ofinterest analysis to compare these patients with healthy controls. Voxel-based morphometry was used to determine macroscopic differences in gray and white matter volume between patient groups. Setting: University-affiliated research institution. Participants: A total of 20 drug-naive patients with PD (10 with tremor-dominant PD and 10 with nontremordominant PD) and a total of 20 healthy controls. Main Outcome Measures: Blood oxygenation level- dependent activation and percent signal change. Results: Robust findings across both voxelwise and region- of-interest analyses showed that, compared with patients with tremor-dominant PD, patients with nontremordominant PD had reduced activation in the ipsilateral dorsolateral prefrontal cortex, the globus pallidus interna, and the globus pallidus externa. Region-ofinterest analyses confirmed that patients with nontremordominant PD had reduced activity in the ipsilateral dorsolateral prefrontal cortex, the globus pallidus interna, and the globus pallidus externa compared with patients with tremor-dominant PD and healthy controls. Patients with tremor-dominant PD had increased activity in the contralateral dorsolateral prefrontal cortex compared with patients with nontremor-dominant PD and healthy controls. These results could not be explained by differences in gray or white matter volume. Conclusions: Reduced brain activity occurs in the prefrontal cortex and globus pallidus of patients with nontremor-dominant PD compared with both patients with tremor-dominant PD and healthy controls, which suggests that functional magnetic resonance imaging is a promising technique to understand differences in brain activation between subtypes of PD.