To describe the management of stimulation-refractory gait freezing in Parkinson’s disease (PD) patients undergoing deep brain stimulation (DBS) of the globus pallidus internus (GPi).

Gait freezing gait is a recognized stimulation-induced phenomenon with DBS of the  subthalamic nucleus for PD and GPi for dystonia; however, limited reports exist of this complication following GPi DBS for PD.

An IRB-approved retrospective chart review was conducted of patients who experienced freezing of gait after programming of bilateral GPi DBS for idiopathic PD. We collected demographic, and phenotypic data, exam findings, stimulation parameters and total electrical energy delivered from each visit since time of stimulator placement to the last follow-up. We then classified the etiology of gait symptoms.

6 subjects (3M) met inclusion criteria, 3 tremor-dominant, 3 postural instability gait disorder subtype. Mean MDS-UPDRS-III (n=5) before stimulator placement was 69 +/- 13 on medication, 27 +/- 7 SD off medication. 5 subjects experienced gait freezing before DBS, 1 with on-period freezing, and all showed initial improvement after programming. Subjects underwent DBS surgery an average of 12 +/- 4 years after initial PD diagnosis, and refractory gait freezing began an average of 358 +/- 295 days after first DBS calibration. Freezing in 3 subjects was stimulation-induced, 2 due to disease progression and 1 due to suboptimal lead position with stimulation-limiting capsular effects. Medication and stimulator adjustments (higher and lower) were tried in all patients. Physical therapy helped 2/4 patients. In the three patients with stimulation-induced freezing, gait improved with reduced TEED (mean TEED 168.2 +/- 90.0 with gait freezing vs. 61.6 +/- 19.8 after re-programming).

Our study demonstrates three patterns of gait freezing following GPi DBS for PD: stimulation-induced, disease progression, and suboptimal lead position. Diagnostic strategies include stimulator and medication adjustment, assessment on/off meds and stim, and assessment of lead position.