Probabilistic mapping of gait changes after STN-DBS for Parkinson’s disease

Abstract

Abstract Objective. Gait disturbances causing impaired mobility are common in Parkinson’s disease after bilateral deep brain stimulation of the subthalamic nucleus. We describe subthalamic subregions where neurostimulation had a positive effect on gait or provoked gait disturbances. Methods. Sixty-eight patients were classified according to postoperative gait changes: (1) gait improvement, (2) no change, (3) de novo gait disturbances. We performed a segregation analysis for (1) and (3) by simulating volumes of tissue activated and comparing aggregated spatial data for the two groups and calculated probability maps to forecast gait performance and the parkinsonism control. Results. Twenty patients experienced complete remission of presurgical gait problems after stimulation. Nine patients showed de novo gait disturbances one year post-implantation. Active contacts were more ventrally located for de novo gait disturbances versus gait improvement. Strong correlations were found between clinical alterations in gait and the individual stimulation volume within the probabilistic outcome gait map (R2 = 0.78; p = 0.01), whereby clinical improvement in parkinsonism correlated with individual stimulation volume within the corresponding probabilistic outcome map (R2 = 0.39; p = 0.01). The probabilistic maps predict patients who experience long-term gait benefits based on their volume of tissue activated overlap, which was gait specific and showed no correlation with the global parkinsonism control heatmap. Interpretation. Probabilistic mapping showed high correlation for therapy outcomes, especially gait improvement. The concept of sweet- or badspots could not explain individual differences. The thin delineations between close substructures in the subthalamic nucleus correlated with individual gait changes after neurostimulation. Probabilistic mapping may direct future re-programming approaches for greater mobility in parkinsonian patients.