Imaging of Facial Muscles in Facioscapulohumeral Muscular Dystrophy: An Exploratory Study Comparing Magnetic Resonance Imaging and Ultrasound

AIMS: Facioscapulohumeral muscular dystrophy (FSHD) is a genetic progressive muscle disorder often presenting with facial weakness. However, imaging studies specifically evaluating facial muscle involvement and its relationship with clinical severity remain limited. This preliminary study explored magnetic resonance imaging (MRI) and ultrasound (US) assessment of facial muscle involvement and correlations with clinical severity. METHODS: This single-center prospective study enrolled 12 genetically confirmed FSHD1 patients (mean age 57.8 years). Clinical evaluation included the FSHD score, Comprehensive Clinical Evaluation Form (CCEF), and Facial Weakness Score (FWS). Muscle thickness of the orbicularis oris (OOr) and zygomaticus major (ZMj) was measured on both MRI and US, while MRI was additionally used for qualitative assessment of muscle bulk. Inter-rater reliability was assessed for imaging measurements. RESULTS: MRI and US showed comparable facial muscle thickness, with mean ZMj thickness of 2.34 ± 0.75 mm and 2.12 ± 0.55 mm, and OOr thickness of 2.28 ± 0.70 mm and 2.20 ± 0.67 mm, respectively. Inter-rater reliability for MRI was high (ICC = 0.84), and reduced ZMj thickness showed moderate to strong correlation with greater disease severity (ρ up to 0.87, p < 0.001) and impaired facial gestures (ρ = 0.50-0.77, p < 0.05). DISCUSSION: Despite the small sample size, MRI, and US assessment of facial muscles correlated with clinical severity and functional outcomes in FSHD, supporting their use as complementary tools. Longitudinal studies are required to establish imaging's role in monitoring changes over time.