Skeletal muscle ultrasonography in children with a dysfunction in the oxidative phosphorylation system

Objective: The aim of this prospective study was to investigate the diagnostic value of quantitative skeletal muscle ultrasonography in children suspected of having a mitochondrial disorder. Methods: Muscle thickness and quantitatively determined echo intensity of four muscles were established in 53 children with symptoms indicative of a mitochondrial disorder. Results: A sensitivity of 25 to 46% was found, depending on the chosen cut-off point (abnormal or borderline abnormal), with a specificity of 85 to 100%. Except for one, all abnormal ultrasound scans were found in children over five years of age. Within the group of patients with a mitochondrial disorder, a significant correlation was found between muscle echo intensity and age (r = 0.38; p = 0.047). Conclusions: We conclude that skeletal muscle ultrasound can be of additional value in the diagnosis of children with suspected mitochondrial disorders, especially in children over five years of age. With its low sensitivity, it is not suitable for screening purposes. However, since all abnormal ultrasound scans were found in children with a mitochondrial disorder, and no significant correlation with the MDC score was found, muscle ultrasound can be used complementary to this scoring system to facilitate the decision-making in pursuing further invasive diagnostics.