Objective: This study aimed to characterize turning performance and clinical characteristics in people with definite, probable or no Freezing of Gait (FoG) in a cohort of people with Parkinson’s disease (PD).

Background: FoG is common and debilitating in people with Parkinson’s disease (PD). Both clinical decision-making and pathophysiology research are based on classification of patients as ‘freezers’ or ‘non-freezers’.The question is whether these states are clearly distinct or there is a continuum of freezing with progressive worsening. We recently introduced an objective measure of FoG, FoG Ratio, based on the ratio of leg frequencies (0.5-3Hz and > 3 Hz) during a 360° turning in place task. Higher leg frequencies represent freezing, which could be helpful in tracking a potential continuum spectrum from absent to severe FoG.

Method: One hundred and forty-seven people with PD (Age: 69±8) off medication, and eighty-three healthy controls (Age: 68.5±8) turned 360° in place for 2 minuteswhile wearing three wearable sensors (one on each shin and one on the waist)that were used to calculate FoG Ratio. People with PD were classified as: ‘definite freezers’, new FoG questionnaire (NFOGQ) score >0 and clinically observed FoG (N=42, MDS-UPDRS III: 48±13), ‘non-freezers’, NFOGQ=0 and no FoG clinically observed (N=81, MDS-UPDRS III: 36±11); and ‘probable freezers’, either NFOGQ>0 but no FoG observed or NFOGQ=0 but FoG observed (N=24, MDS-UPDRS III: 43±9). To investigate whether the FoG Ratio differed between groups, linear mixed-models were fit accounting for disease severity (MDS-UPDRS Part III) as a covariate.

Results: A significant group effect (p<0.05) was found for FoG Ratio during turning. Figure 1 shows that FoG Ratio during turning was significantly higher in people with definite FoG compared to non-freezers (p<0.001), similar among people with probable FoG and non-freezers (p=0.10) as well as between people with probable FoG and definite FoG (p=0.04). In addition, FoG Ratio in both definite and probable FoG was higher than in healthy controls (p<0.01).

Conclusion: These preliminary findings suggest that an increase in FoG Ratio, objectively assessed with wearable sensors during a turning in place test, may be of help in characterizing people with PD transitioning from non-freezers to freezers. Future work is needed to examine video recordings and understand if there is a spectrum of FoG Ratio across the groups with higher FoG Ratio indicating more severe FoG.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/freezer-or-non-freezer-what-is-in-between/