Phenotyping Functional Gait Disorder: An Exploratory Analysis of Existing Frameworks

Area of Science:

• Neurology
• Clinical assessment
• Movement disorders

Background:

• Functional neurological disorder (FND) presents significant gait impairment.
• Current classification methods for functional gait disorder (FGD) phenotypes lack standardization.
• Six phenotypic frameworks have been proposed but their efficacy is unproven.

Purpose of the Study:

• To assess the utility of existing frameworks in classifying FGD videos.
• To determine inter-rater reliability for these classifications.
• To identify limitations in current FGD phenotyping.

Main Methods:

• Observational study design with inter-rater reliability assessment.
• Five raters evaluated 34 FGD videos using six distinct phenotypic frameworks.
• Krippendorf's alpha was employed to quantify inter-rater agreement.

Main Results:

• The Fung (2016) and Baik and Lang (2007) frameworks showed the highest classification rates (85% and 82%).
• Other frameworks classified between 53-65% of videos.
• Consistently low inter-rater agreement was observed across all frameworks (K-alpha: 0.287-0.507).

Conclusions:

• Current phenotypic frameworks demonstrate limited ability to categorize FGD videos comprehensively.
• No single framework could classify all observed cases.
• Low inter-rater reliability highlights the need for a more robust and standardized classification system for FGD.