Characterizing the face in facioscapulohumeral muscular dystrophy

Abstract

Objective: To evaluate facial weakness in patients with FSHD to better define clinical signs, and pilot a facial weakness severity score.

Methods: 87 FSHD patients and 55 controls were video recorded while performing seven facial tasks. The videos were assessed by three independent examiners to compile an overview of signs of facial weakness. Next, videos were semi-quantitatively assessed using a newly developed 4-point facial weakness score (FWS). This score was evaluated and correlated to other FSHD disease characteristics.

Results: Patients had lower scores on the total FWS than controls (mean score 43 ± 28, range 4-118, vs 14 ± 9, range 0-35, p < 0.001) and on all seven individual facial tasks (all p < 0.001). 54% of patients had FWS scores outside the range of controls. Patients had more asymmetry between the left and right side of the face than controls. About 10% of the patients had very mild facial weakness. These were mostly males (89%) with longer D4Z4 repeat sizes of 7-9 units. More severe facial weakness correlated to more severe overall disease severity and shorter D4Z4 repeat size, but not to disease duration. Interobserver agreement for the FWS between three raters was low with a Fleiss Kappa of 0.437.

Conclusion: This study provides an overview of the clinical spectrum of facial weakness and its relation to other disease characteristics. The 4-point scale we introduced to grade the severity of facial weakness enables correlation of facial weakness to disease characteristics, but is not suited as clinical outcome measure for longitudinal studies.

Keywords: Facial weakness; Facioscapulohumeral muscular dystrophy; Outcome measures.

Fig. 1

Face in rest and facial tasks in one of the controls. a Resting position; b closing the eyes gently; c closing the eyes firmly; d raising the eyebrows; e frowning; f pursing the lips; g showing the teeth and h puffing of the cheeks

Fig. 2

Examples of moderate and severe facial weakness per task (image taken of maximal movement possible)

Fig. 3

Facial weakness score per individual participant ranked per group from lowest to highest score

Fig. 4

Sum of absolute differences in FWS between observers per individual. For individuals with moderate weakness the variability between observers is higher than for individuals with mild and severe weakness

Fig. 5

Examples of subtle signs of facial weakness. a Signe de cils right eye (inability to bury the eyelashes completely when attempting to close the eyes tightly). b Asymmetry in raising the corners of the mouth with left corner being raised less high. c Asymmetry when pouting the lips due to right sided weakness of the muscles around the mouth. d Difficulty puffing the cheeks. Notice the asymmetry and the lips being sealed horizontally