To report the results of expanded pulmonary assessments in patients with generalized myasthenia gravis (GMG) gathered in the neuromuscular clinic.

Muscle weakness leading to respiratory involvement can occur in patients with GMG, however, most scales assessing severity of myasthenia have limited methods of determining presence and extent of respiratory dysfunction. Seated forced vital capacity (FVC) is the most commonly used test to measure restrictive pattern dysfunction in MG, however, may not be sensitive enough to evaluate diaphragm dysfunction.

One hundred and thirty-seven patients ages 18 to 92 and mean duration of MG of 18.2 years and disease severity ranging from asymptomatic GMG to severe disease (mean MG-QOL 16.1) were included in the study. Excessive daytime sleepiness, measured by the Epworth scale, was present in 18% of patients. There was a relatively low burden of respiratory symptoms measured by the UCSD-SOB scale (mean score 23 out of a maximum score of 120), and the MRC Dyspnea scale (mean score 1 out of a maximum score of 4). Thirty-three percent of patients had abnormal seated FVC and an identical number had abnormal supine FVC.

Outpatients with GMG have a low burden of respiratory complaints, however, nearly 1 in 5 patients have excessive daytime sleepiness and one third of patients have abnormal vital capacity. No additional benefit to testing FVC in the supine position was shown in this study.