[Evaluation of the vocal tract during Japanese vowel production in myasthenia gravis using magnetic resonance imaging].

We report a 65-year-old Japanese female whose primary symptom of myasthenia gravis was related to rhinolalia aperta. The vocal tract during vowel production was evaluated using two-dimensional fast advanced spin echo (2D-FASE) MR images on supine and prone position. Before treatment, MRI on prone position demonstrated anterior shift of the palatine uvula and the tongue during Japanese "a", "u" and "o" production following the gravity, the former suggested the paresis of the sphenosalpingostaphylinus and elevator veli palatini muscle and the latter the paresis of the styloglossal and hypoglossal muscles. After treatment of steroid pulse and immune absorption, 2D-FASE images on prone position revealed the normalized configuration of the tongue and the soft palate during the Japanese five-vowel production. Kinetic MRI may be useful for evaluation of dynamics of the tongue and the soft palate.