How to Annotate Freezing of Gait from Video: A Standardized Method Using Open-Source Software

Abstract

Visually scoring freezing of gait (FOG) from video is increasingly recognized as the gold-standard for assessing FOG severity in Parkinson's disease. Surprisingly, no guidelines exist on how to visually score FOG. Here, I present a free template that can be implemented in open-source software to annotate FOG from video. I provide a user guide on how to implement the template and standardize the scoring of FOG and the percentage of time spent with FOG (%FOG). It is hoped that by disseminating this method investigators will be better able to employ %FOG as an outcome in their studies and therapeutic trials.

The New Freezing of Gait Questionnaire: Unsuitable as an Outcome in Clinical Trials?

“…The NFOG‐Q scores did not correlate with either the duration ( r = 0.35, P = 0.095) or frequency ( r = 0.30, P = 0.15) of the video‐rated procedure. Several studies suggested that video annotations of FOG‐provoking tasks could be used as the gold standard for rating freezing severity . However, this method is very labor intensive as it should ideally be done by at least 2 independent raters in a standardized manner to allow for comparison between studies .…”

“…Therefore, in the future, the field needs to move toward unobtrusive home‐based assessment of FOG using digitized mobility outcomes, as was recently suggested by Mancini and colleagues . Combining video annotations with wearable sensor‐based data collected during standardized tests will permit the necessary validation of FOG algorithms for domestic use, allowing data collection spanning for much longer time periods (days or potentially even weeks) . Whether objectively and remotely measured FOG detection during spontaneous daily mobility is suitable as a primary outcome for clinical trials (with good test‐retest and MDC values) remains to be determined.…”

“…Several studies suggested that video annotations of FOG-provoking tasks could be used as the gold standard for rating freezing severity. [45][46][47] However, this method is very labor intensive as it should ideally be done by at least 2 independent raters in a standardized manner to allow for comparison between studies. 46,47 Automated video algorithms may enable faster and standardized FOG video annotations.…”

“…[45][46][47] However, this method is very labor intensive as it should ideally be done by at least 2 independent raters in a standardized manner to allow for comparison between studies. 46,47 Automated video algorithms may enable faster and standardized FOG video annotations. 48 However, the testing effect elicited by standardized assessments in a laboratory or a home setting may preclude many FOG episodes from occurring, even when off medication.…”

Freezing of Gait in People with Parkinson’s Disease: Nature, Occurrence, and Risk Factors

“…The main strength of this study is the volume of captured gait interruptions that included over 550 freezes, cognitive stops and stumbles from a series of walks that varied in cognitive and motor complexity. We used definitions and terminology similar to that described in recent study that also used video recording to document FOG episodes [44]. One difference relates to the commencement of FOG where Gilat defined FOG starting when the foot no longer takes an effective step, whereas we took the last heel strike of the last full step as the FOG commencement point as it is easier to precisely identify.…”