Revisiting Stimulation Polarity in Subthalamic Deep Brain Stimulation: Monopolar Anodic Programming for Freezing of Gait and Tremor Refractory to Cathodic Stimulation—A Case Series and Focused Clinical and Mechanistic Review

Background Tremor and freezing of gait (FOG) are two disabling symptoms that may defy currently available medical or stimulation therapies in some patients with Parkinson’s disease (PD). Objective To evaluate the effects of anodic stimulation in treatment-resistant FOG and tremors in PD patients undergoing STN DBS. Materials and Methods Five PD patients, four with treatment-refractory FOG and one with recurrent tremor, following bilateral STN-DBS were systematically assessed under both cathodic and anodic stimulation, with all other stimulation parameters held constant to isolate polarity-dependent effects. Results Compared with conventional cathodic stimulation, anodic stimulation was associated with clinically meaningful improvement in FOG and tremor in this selected cohort. Conclusion Anodic stimulation (AS) may offer an alternative programming strategy for resistant FOG and tremor cases. The findings need to be further confirmed by mechanistic and longitudinal studies integrating imaging, neurophysiology, and computational modeling to optimize individualized therapy.