Objective:

Background:

Deep brain stimulation of the STN and GPi are highly effective therapies for medication-refractory Parkinson disease and dystonia. The relationship between the volume of these structures and DBS thresholds remains incompletely understood.

Design/Methods:

We conducted a retrospective review of people with STN or GPi DBS at the University of Florida. High-resolution T1 MPRAGE scans were collected for each patient. Individualized brain anatomy was characterized by warping the CIT168 basal ganglia atlas to each patient’s MRI using a 3-stage transformation within Advanced Normalization Tools. The coregistrations were manually verified and refined to include voxel intensities above 0.8. STN, GPi, and globus pallidus externus (GPe) volumes were calculated by summing non-zero voxels and multiplying by voxel volume. We calculated the Pearson correlation coefficient to measure the correlation between DBS target volume and side effect threshold at the four different lead contacts.

Results:

Forty-five STN DBS leads representing 39 unique patients and 153 GPi DBS leads representing 89 unique patients were analyzed. For the STN, no significant correlations were identified. For the GPi, there were significant positive correlations between GPi volume and side effect threshold at contacts two (r=0.17, p=0.03) and three (r=0.20, p=0.02). Additionally, there were significant correlations between GPe volume and side effect threshold at contacts one (r=0.17, p=0.03), two (r=0.27, p=0.0009), and three (r=0.27, p=0.0007) in subjects with GPi DBS.

Conclusions:

Subjects with smaller GPi and GPe volumes have narrower thresholds for stimulation-induced side effects at the more dorsal contacts. GPi and GPe volume could be important considerations when interpreting monopolar review data in the clinic and when assessing adequate lead placement for GPi DBS in the operating room.