Objective: To describe brain metabolic activity changes during dynamic obstacle avoidance in parkinsonian patients with subthalamic deep brain stimulation (STN-DBS)

Background: STN-DBS does not offer the same improvement to gait disturbances as it does on the cardinal Parkinson’ disease (PD) symptoms of bradykinesia, rigidity and tremor. A possible cause of this shortcoming is our limited understanding of the supraspinal locomotion control, particularly during gait modulation. Molecular imaging offers the opportunity to disentangle the neural correlates of supraspinal locomotion control and describe how they are modulated by DBS [1]. We leveraged this possibility for the study of gait modulation.

Method: Six PD patients (age 59±9; disease duration 11±3; UPDRS-III: 41±15) with bilateral STN-DBS underwent three positron-emission tomography (PET) scans with (18)F-fluorodeoxyglucose (FDG) after overnight suspension of antiparkinsonian medications. A first FDG-PET was performed at rest in stim-off condition. The second and third FDG-PET were performed after a dynamic obstacle avoidance task in stim-off and stim-on condition, respectively. We used a fully-immersive virtual reality environment where subjects have to adjust their walking pattern to avoid collision with a virtual agent crossing their gait trajectory [2]. The gait task was started 10 min before FDG injection and continued for 20 minutes until the PET examination. FDG-PET images were co-registered with MRI and analyzed with SPM12 (clusters ≥50 voxels and uncorrected p<0.001).

Results: Compared with the resting state, modulation of gait elicited, in both stim-off and stim-on conditions, increased metabolic activity in the cerebellum, postcentral gyri, and precuneus as well as hypometabolism in the right caudate nucleus. Active STN-DBS determined a selective activation of the right superior frontal and the left middle orbitofrontal gyri, which associated with improved gait pattern in all patients.

Conclusion: We report a selective pattern of metabolic activation of the supraspinal locomotor network in parkinsonian patients using a highly standardized protocol closely resembling an everyday life scenario. Our preliminary analysis suggests a direct impact of STN-DBS on the activity of frontal cortical regions for proper overcoming of dynamic obstacles.

References: [1] Weiss PH, et al. Mov Disord. 2015;30(8):1121-1125. [2] Palmisano C, et al. Front Hum Neurosci. 2022;16:783452.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/the-impact-of-stn-dbs-on-brain-metabolic-activity-during-dynamic-obstacle-avoidance-in-parkinsons-disease/