Muscle imaging in facioscapulohumeral muscular dystrophy research: A scoping review and expert recommendations.

Clinical trial readiness is an important topic in the field of facioscapulohumeral muscular dystrophy (FSHD). As FSHD is a slowly progressive and clinically heterogeneous disease, imaging biomarkers have been proposed to complement clinical outcome measures. Muscle magnetic resonance imaging (MRI), ultrasound and dual energy X-ray absorptiometry (DEXA) have been used to measure disease severity, activity and progression. We conducted a scoping review of the literature on these imaging modalities to assess gaps in knowledge and subsequently collaborated with a panel of neuromuscular imaging experts to generate recommendations on the road ahead. We systematically searched PubMed, EMBASE and Cochrane Library databases. Three-hundred and twenty-eight studies were screened and one hundred and five studies were included. MRI indices related to intramuscular fat content, STIR positivity and T2 are used as diagnostic as well as prognostic and monitoring biomarkers. Ultrasound echogenicity can be used as a diagnostic and potentially as a prognostic and monitoring biomarker. DEXA lean muscle mass may be used as an additional monitoring biomarker. Each imaging modality has its own benefits but also challenges. Based on our expert opinions, we propose a roadmap to address these challenges, ensuring the optimal use of each modality in multi-center clinical trials in FSHD.