[Electroglottographic studies in myasthenia gravis patients--swallowing in exacerbation and remission stage]

We quantitatively evaluated the electroglottographic changes in swallowing in patients with generalized myasthenia gravis during exacerbation and remission stages. Five patients with myasthenia gravis (Osserman's stage IIB, 55.3 +/- 3.1 years old) and 6 healthy control subjects (55.3 +/- 1.1 years old) were examined. The instrument delivered a 450 microA. 52 kHz carrier signal to a pair of surface electrodes on each side of the larynx at the level of the thyroid lamina. Tissue impedance across the neck was recorded via electroglottography (EGG) while swallowing 10 ml of water. Four trials were performed for each subject, and the EGG waveform was analyzed. The EGG waveform during the exacerbation stage exhibited a more significantly increased number of phases and longer duration than that during remission. In myasthenia gravis patients, the number of phases and the duration from exacerbation to remission was more significantly reduced than those in controls at an interval of 3 years (p < 0.001, p < 0.02). These findings suggest that changes in the number of phases and duration of the EGG waveform are objective and quantitative parameters for measuring therapeutic effectiveness in treating swallowing disturbance due to myasthenia gravis. EGG is a useful and noninvasive technique for evaluating swallowing change in myasthenia gravis patents.