Characterizing the face in facioscapulohumeral muscular dystrophy

Area of Science:

• Neurology
• Genetics
• Clinical Research

Background:

• Facioscapulohumeral Dystrophy (FSHD) is a genetic myopathy characterized by progressive muscle weakness.
• Facial muscle involvement is a hallmark of FSHD, significantly impacting patients' quality of life.

Purpose of the Study:

• To comprehensively evaluate facial weakness in FSHD patients.
• To define the clinical spectrum of facial weakness in FSHD.
• To pilot a novel 4-point facial weakness score (FWS) for assessing severity and correlating it with disease characteristics.

Main Methods:

• Video recordings of 87 FSHD patients and 55 controls performing seven facial tasks.
• Assessment of facial weakness signs by three independent examiners.
• Semi-quantitative scoring using a newly developed 4-point facial weakness score (FWS).

Main Results:

• FSHD patients exhibited significantly lower FWS scores and poorer performance on all facial tasks compared to controls (p < 0.001).
• 54% of FSHD patients displayed FWS scores exceeding the control range, with increased facial asymmetry noted.
• Mild facial weakness in FSHD was associated with male gender and longer D4Z4 repeat lengths (7-9 units).
• More severe facial weakness correlated with greater overall disease severity and shorter D4Z4 repeat lengths, independent of disease duration.

Conclusions:

• The study delineates the clinical variability of facial weakness in FSHD and its relationship with disease markers.
• The developed 4-point FWS facilitates correlation between facial weakness and FSHD characteristics.
• The FWS is not recommended as a clinical outcome measure for longitudinal studies due to low interobserver agreement (Fleiss Kappa = 0.437).