Contractile properties are impaired in congenital myopathies

• Published in: Neuromuscular disorders : NMD 2020-08, Vol.30 (8), p.649-655
• Main Authors: Eisum, Anne-Sofie Vibæk, Fornander, Freja, Poulsen, Nanna Scharff, Andersen, Annarita Ghosh, Dahlqvist, Julia, Andersen, Linda Kahr, Witting, Nanna, Vissing, John
• Format: Article
• Language: English
• Subjects: Congenital myopathy; Contractile cross-sectional area; Dixon technique; Muscle contractility
• ISSN: 0960-8966; 1873-2364
• DOI: 10.1016/j.nmd.2020.06.007

•Contractility is reduced in most muscles in congenital myopathy.•Contractility is impaired in both sarcomeric and non-sarcomeric protein defects.•Fat replacement does not affect muscle contractility in congenital myopathy. The ratio between muscle strength and muscle cross-sectional area is called the specific force. Fatty replacement of muscles is seen in many myopathies, affecting the specific force, without necessarily affecting the ability of the remaining muscle fibers to contract. This ability is called the contractility and is the ratio between muscle strength and the lean muscle cross-sectional area, i.e. the contractile cross-sectional area. We hypothesized that contractility is disrupted in patients with congenital myopathy, because of defects in contractile proteins of the sarcomere. Peak torque across ankle and knee joints was measured by isokinetic dynamometry in 16 patients with congenital myopathy and 13 healthy controls. Five patients only participated partially in the dynamometer measurements due to severe muscle weakness. Dixon MRI technique was used to quantify muscle fat fractions and calculate cross-sectional area. Patients with congenital myopathy had lower cross-sectional area in all muscle groups (P