Muscle Strength, Balance, and Indoor Mobility in Oculopharyngeal Muscular Dystrophy: An Exploratory Canadian Multicenter Study

INTRODUCTION/AIMS: Oculopharyngeal muscular dystrophy (OPMD) is a neuromuscular disease presenting with dysphagia, ptosis, and proximal weakness. Muscle strength and indoor mobility capacity have rarely been studied using standardized clinical outcome assessments (COAs). The objectives of this study were to (1) document muscle strength, balance, and indoor mobility, and (2) explore factors contributing to indoor mobility limitations. METHODS: This cross-sectional study included 113 participants (mean age = 61.8 years) from four Canadian neuromuscular disease clinics (Saguenay, Quebec, Montreal, Ottawa). The COAs included upper and lower limb quantified muscle testing, Activities Balance and Confidence Scale, BERG Balance Scale, and for indoor mobility the 10-m Walk Test at self-selected (10mWTs-s) and maximal speed (10mWTm), 30-s Sit-to-Stand test (30s-STS), and 10-step stair test. Multiple linear regression models using backward selection were used to explore factors associated with each indoor mobility COA. RESULTS: Muscle strength in percentage of age- and sex-matched reference values ranged from 41.4% to 81.4%, hip flexors being the most severely impaired muscle group. The 10mWTs-s, 10mWTm, 30s-STS and 10-step stair test had percentages of reference values ranging from 44.9% to 83.3%. Balance, balance confidence, and lower limb muscle strength were found to be significant factors for all indoor mobility COAs. All models explained between 57.4% and 79.9% of the variance. DISCUSSION: This study provides clinically relevant outcome measures for assessing mobility in OPMD and identifies key factors that should be targeted in rehabilitation. These findings may also inform the selection of outcomes for future interventional studies.