Clinical patterns of gait freezing in Parkinson's disease and their response to interventions: An observer-blinded...

Freezing of gait (FOG) in Parkinson's disease (PD) is provoked by specific situations. The sensitivity of these situations to detect FOG and the relative FOG response to l-dopa and subthalamic nucleus deep brain stimulation (STN-DBS) is unknown.

Two blinded reviewers analyzed the video recordings of a standardized patient assessment before and 10 months after DBS-implantation of 124 PD patients with positive FOG according to the Unified Parkinson Rating Scale part II item 14. Baseline evaluations were done under 2 conditions (OFF- and ON-drug states). Postoperatively, the patients were evaluated under 4 conditions (OFF-drug/OFF-stim, OFF-drug/ON-stim, ON-drug/OFF-stim, and ON-drug/ON-stim). FOG frequency and its severity was rated during different provoking situations (start, turning, reaching a destination and open space hesitations) during a standardized walking task. Cumulative link mixed models were calculated to investigate the immediate and carry-over effect of medication and stimulation.

Eighty-one percent of patients presented FOG at least in one provoking situation on video assessment. During turning, the FOG severity was significantly worse than for the other subtypes (p < 0.0001). Both interventions improve all FOG subtypes similarly. The effect size of l-dopa and STN-DBS on subtypes were similar (p > 0.05), but the combined intervention had a stronger effect on FOG severity (p < 0.0001) compared to each intervention separately. FOG severity was lower at follow-up OFF compared to baseline OFF condition (p < 0.02) demonstrating a carry-over effect of STN-DBS.

Turning is the most sensitive provoking situation for gait freezing. STN-DBS and l-dopa improve all FOG subtypes similarly, their effect is stronger in combination.