Objective: Determine the validity of a ‘freezing-provoking protocol’ (FOG-PP) in the home setting and assess the effects of medication on freezing of gait (FOG) during several FOG-triggers in people with Parkinson’s disease.

Background: FOG is difficult to elicit in a laboratory due to 1) its episodic nature, 2) its complex relation with dopaminergic medication, and 3) the so-called white-coat effect. Here, we aim to test the validity of percentage time frozen (%TF) during a FOG-PP in the home setting when OFF and ON medication.

Method: A FOG-PP was performed by 29 freezers after overnight withdrawal of antiparkinsonian medications (OFF) and 1 hour after regular drug intake (ON). It consisted of: four-meter walk back and forth (4MW), the Timed Up and Go test (single task/dual-task (ST/DT)), 360° turning in place in alternating directions (ST/DT), negotiating a narrow doorway, and moving in a FOG ‘hotspot’, defined as the patient’s location that most often provoked FOG. The New FOG Questionnaire (NFOG-Q) was used as the gold standard to determine construct validity of the FOG-PP.

Results: Patients were on average 68.7±6.3 years old, had a disease duration of 11.7±6.9 years, and an NFOG-Q score of 21.4±3.9. All subjects had FOG in OFF and 18/29 had it in ON, amounting to a total of 725 episodes and 65.1 minutes of FOG. The NFOG-Q score was related to %TF in OFF (ρ=0.47, p=0.01), but not in ON. There was no significant difference between ST and DT conditions. 360° turns provoked the most FOG, which was significantly different from all other conditions in OFF except for the hotspot. In ON, only the difference between 360° turns and 4MW remained significant after multiple comparison correction (Fig. 1). Four patients did not have FOG during 360° turns. %TF was significantly different between OFF and ON for all conditions, except for the 360° turns (Table 1).

[Figure1]
[Table1]

Conclusion: Construct validity was confirmed against the NFOG-Q for %TF in OFF and was higher in OFF, underscoring the importance of OFF tests to objectively capture and evoke FOG. Still, over 60% of patients had FOG in ON. The 360° turns proved the most effective trigger. All FOG-triggers were sensitive to medication effects, apart from the 360° turns suggesting a different underlying mechanism. We conclude that %TF from a FOG-PP in patient homes is a valid outcome.

« Back to MDS Virtual Congress 2021

MDS Abstracts - https://www.mdsabstracts.org/abstract/medication-effects-and-validity-of-home-based-freezing-tests-in-parkinsons-disease/