Quantitative assessment of muscle atrophy and structural changes in children with spinal muscular atrophy using ultrasound imaging

Abstract

Background: Spinal muscular atrophy (SMA) in children is a hereditary neuromuscular disorder characterized by motor neuron degeneration, which leads to progressive muscle weakness and impaired movement. Ultrasound imaging, owing to its non-invasive, radiation-free, and cost-effective nature, provides an invaluable tool for visualizing muscle morphology. This technique offers a significant advantage in the clinical evaluation of SMA. The aim of this study was to quantitatively assess muscle abnormalities in children with SMA using both conventional ultrasound and shear wave elastography (SWE), and to explore the potential of these imaging modalities in the assessment of the disease.

Methods: A total of 20 patients with type II or III SMA, who had not received any prior disease-modifying treatment (DMT), were included in the SMA group. These patients were enrolled between May 2022 and January 2024. The control group comprised 20 healthy children matched for age and gender. Muscle thickness (MT) and shear wave velocity (SWV) of the biceps brachii (BB) and quadriceps femoris (QF) were measured using B-mode ultrasound and SWE. Ultrasound parameters were compared between children with SMA and healthy controls. Additionally, motor function in the SMA group was assessed using the Hammersmith Functional Motor Scale Expanded (HFMSE), and the correlation between ultrasound parameters and HFMSE scores was analyzed.

Results: The BB-MT, BB-SWV, QF-MT and QF-SWV in the SMA group, were significantly lower than those in the control group (p = 0.030, 0.000, 0.004, and 0.001, respectively). Correlation analysis revealed a significant positive correlation between QF-MT and QF-SWV in the SMA group and the HFMSE score (r = 0.802, p = 0.000; r = 0.56, p = 0.000, respectively).

Conclusions: Ultrasound imaging is an effective modality for detecting and quantifying muscle atrophy and structural changes in children with SMA. Moreover, it demonstrates a significant correlation with motor function, providing valuable insights into the clinical assessment of SMA.

Keywords: B-mode ultrasound; Motor function; Muscle thickness; Shear wave elastography; Spinal muscular atrophy.