Implementation of a markerless motion analysis method to quantify hyperkinesis in males with fragile X syndrome

- Use of a markerless motion analysis system to quantify hyperkinesis.
- Outcome variables track travel distance of limb segments relative to body COM.
- Outcome variables discriminate normal from FXS cohort.
- Outcome variables correlate with clinical rating scales for hyperkinesis.

Hyperactive behavior - and implicitly, motion - in Fragile X syndrome (FXS) has been historically described using behavioral rating scales. While rating scales are the current standard outcome measures used in clinical research, they have limitations including their qualitative nature and subjectivity. The advent of new motion capture technologies has provided the opportunity to develop quantitative methods for measuring hyperactive motion. The hypotheses for this study were that a novel markerless motion analysis method (1) can quantitatively measure kinematic parameters, (2) can differentiate the level of hyperkinesis between control and FXS populations, and (3) will correlate with blind-reviewer synchronous video-capture methods and behavioral rating scale scores. Twenty young males (7-control, 13-FXS; ages 9-32) were studied using a standardized protocol in a markerless motion analysis suite. Behavioral scale questionnaires were filled out by parents and those scores were correlated with motion parameters (frequency and total traveled distance) of body segments during 30 s of story listening while standing in the observation space. The markerless system was able to track subjects and the two populations displayed significantly different quantities of motion, with larger amounts of motion in the FXS group (p < 0.05). Pearson's correlation coefficients between frequency counts obtained from the markerless system and rater-based video capture were between 0.969 and 0.996 (p < 0.001). Significant correlations between rating scale scores and motion parameters ranged from 0.462 ≤ r ≤ 0.568 (p ≤ 0.040). These results suggest feasibility and validity of a markerless system as a non-invasive method able to quantify motion in individuals with hyperkinesis.