Computed Tomography Assessment of Diaphragm Thickness in Myasthenia Gravis With Clinical and Functional Correlations

Myasthenia gravis (MG) is an autoimmune disorder of the neuromuscular junction in which respiratory muscle involvement, particularly of the diaphragm, constitutes the principal risk factor for myasthenic crisis and respiratory failure. Objective structural evaluation of the diaphragm in MG remains incompletely standardized. This narrative review synthesizes published evidence on diaphragm thickness measurement in generalized MG, with attention to measurement reproducibility, normative reference values, structural-functional linkages, and potential clinical applications of computed tomography (CT). Studies were identified through a targeted search of peer-reviewed databases covering neuromuscular imaging, diaphragm physiology, and respiratory failure, with emphasis on MG. Studies reporting diaphragm measurements with explicit methodological details or clinical outcomes were prioritized, in both MG cohorts and mixed populations, with particular attention to CT. A small number of studies have used diaphragm ultrasound in MG to assess increased fatigability and predict extubation failure. Direct CT-ultrasound matching in myasthenic patients is lacking; however, in non-myasthenic populations, CT measurements at the L1 vertebral level and at the celiac trunk are reproducible and show consistent associations with ultrasound-derived functional indices of diaphragm dysfunction. Left-sided CT measurements correlate more strongly with multiple functional parameters, whereas right-sided measurements show moderate associations with selected indices. Interobserver agreement for CT is good in non-myasthenic cohorts. Because the available structural-functional evidence derives almost entirely from non-myasthenic, mixed neuromuscular, ICU, or diaphragmatic paralysis cohorts rather than MG-specific populations, these findings are hypothesis-generating: CT-based diaphragm assessment is a candidate structural surrogate for functional impairment in MG and a potential adjunct to risk stratification and therapeutic monitoring. The evidence base remains limited by small cohorts and reliance on mixed disease populations. CT is therefore currently best regarded as complementary rather than definitive, and prospective MG-specific studies, stratified by the Myasthenia Gravis Foundation of America (MGFA) class and antibody subtype (acetylcholine receptor, muscle-specific kinase, low-density lipoprotein receptor-related protein 4, seronegative) and integrated with diaphragmatic compound muscle action potential, diaphragm ultrasound, forced vital capacity, and negative inspiratory force trends, are needed before firm clinical thresholds can be established.