Comparative analysis of thoracic structure and function using CT and dynamic MRI in pediatric thoracic insufficiency syndrome with and without neuromuscular disease.

Abstract

Purpose: Thoracic insufficiency syndrome (TIS) impairs normal respiration and lung growth. In pediatric patients with or without neuromuscular disease (NMD), the relationship between thoracic structure and regional respiratory function remains understudied. We aimed to evaluate these interrelationships using dynamic magnetic resonance imaging (dMRI) and computed tomography (CT).

Methods: This study included 25 pediatric TIS patients: 8 with NMD and 17 without NMD. Thoracic dMRI and CT images were analyzed to quantify intercostal muscle (ICM) volume, skeletal muscle (SM) volume, lung volumes at end-inspiration and end-expiration, chest wall excursion volume, and diaphragm excursion volume. Right-to-left volumetric symmetry ratios were compared using unpaired t-testing, and correlations between structural and functional parameters were assessed using Pearson correlation analysis.

Results: Lung and muscle volumes were generally larger in the TIS-NMD compared to TIS non-NMD, reflecting age-related differences, although lung tidal volumes and diaphragmatic and chest wall excursion volumes were generally similar. The degree of asymmetry reflected by diaphragmatic respiratory function symmetry ratios exceeded that of chest wall symmetry ratios in both groups, with greater disparity in TIS-NMD (3.6 vs 1.8 in TIS-NMD compared to 2.8 vs 2.5 in TIS non-NMD). Correlation between thoracic SM volume and tidal volume was stronger than the correlation between ICM volume and tidal volume in both groups. TIS-NMD patients demonstrated unique compensatory dynamics, including a negative correlation between SM volume and diaphragmatic excursion volume.

Conclusion: Distinct interrelationships exist between thoracic structure and function in TIS patients with and without NMD. These findings suggest that NMD significantly influences respiratory mechanics, emphasizing the role of SM and diaphragm interaction.