The Usefulness of Swallowing Pressure Assessment in the Identification of Mild Pharyngeal Weakness of Myasthenia Gravis: A Case Report

Despite the clinical impact of dysphagia in myasthenia gravis (MG), a standard protocol for diagnosing dysphagia reliably has not yet been established. High-resolution manometry (HRM) provides precise information on pharyngeal pressure. We hypothesized that swallowing pressure assessment using HRM during the edrophonium chloride (EC) test could identify mild bulbar symptoms with no abnormalities on videoendoscopic (VE) and videofluorographic (VF) examination of swallowing, and we tested this hypothesis on a 72-year-old female patient diagnosed with ocular MG who developed slight pharyngeal discomfort over 3 months. The patient's ocular symptoms were stable with pyridostigmine medication. VE and VF revealed no abnormalities. The swallowing pressure along the pharynx was measured using HRM during the EC test. HRM parameters, including velopharyngeal contractile integral and meso-hypopharyngeal contractile integral, were evaluated. These parameters were assessed for three swallows using 3 mL of water. After EC injection, the values of the velopharyngeal contractile integral (78.0 ± 5.4 vs. 134.7 ± 1.3 mm Hg cm·s) and the meso-hypopharyngeal contractile integral were both higher (130.6 ± 1.5 vs. 284.2 ± 11.9 mm Hg cm·s) than those observed before EC injection. Chest computed tomography revealed a thymoma that had not been observed in previous examinations. The patient was diagnosed with thymoma-associated MG. Intravenous immunoglobulin therapy improved the mild dysphagia. We concluded that swallowing pressure assessment during the EC test may be helpful in identifying mild bulbar symptoms in patients with MG.