Effect of intravenous low-osmolality iodinated contrast media on patients with myasthenia gravis

To determine whether the intravenous administration of low-osmolality contrast material is associated with exacerbation of disease-related symptoms in patients with myasthenia gravis.

This HIPAA-compliant, retrospective cohort study was approved by the institutional review board. The requirement to obtain patient consent was waived. Computed tomography (CT) was performed in 267 patients with clinically confirmed myasthenia gravis between January 1, 1995, and December 31, 2011. CT was performed without intravenous administration of contrast material in 155 patients and with intravenous administration of low-osmolality contrast material in 112. Electronic medical records were searched to identify myasthenia gravis-related symptoms before (≤ 14 days) and after (≤ 45 days) each CT examination. The Mantel-Cox log-rank test was used to compare the time to symptom progression between the two groups. The Fisher exact test was used to compare rates of disease-related symptoms during three time periods: (a) 0-1 day after CT, (b) 2-7 days after CT, and (c) 8-45 days after CT.

The unenhanced and contrast-enhanced CT groups had similar thymectomy rates (P = .97) and disease-related symptom trends before CT (P = .58). The contrast-enhanced CT group was associated with a significant reduction in time to disease-related symptom progression following CT (median time to onset of symptom progression, 2.5 days with contrast-enhanced CT vs 14.0 days with unenhanced CT; P = .05). There were significantly more disease-related symptom exacerbations within 1 day of CT in the contrast-enhanced CT group compared with the unenhanced CT group (6.3% [seven of 112 patients] vs 0.6% [one of 155 patients], respectively; P = .01). Acute exacerbations were primarily respiratory (five patients with new-onset dyspnea [four in contrast-enhanced CT group and one in unenhanced CT group], two patients with progressive dyspnea [both in the contrast-enhanced CT group], and one patient with progressive weakness [in contrast-enhanced CT group]). There was no difference in symptoms between groups at 2-7 days (P = .70) or 8-45 days (P = .99).

Intravenous administration of low-osmolality contrast material is significantly associated with exacerbation of myasthenia gravis-related symptoms. Exacerbations most commonly manifest as new or progressive acute respiratory compromise.