Alveolar hypoventilation and hyperosmnia in myotonic dystrophy.

A case of myotonic dystrophy accompanied by alveolar hypoventilation and hypersomnia is presented. Radiological studies and EMG examination of the intercostal muscles demonstrated that the respiratory muscles were affected by the disease, while polygraphic recordings showed that the alveolar hypoventilation and pulmonary hypertension worsened during sleep. The hypersomnia preceded the appearance of clinical signs of the muscular disease by many years and persisted even after treatment when the blood gas analysis values were greatly improved. During both diurnal and nocturnal sleep, the patient frequently fell asleep directly into a REM stage. The possibility is discussed that, concomitant with the respiratory musculature involvement, there is an alteration in the central nervous system in myotonic dystrophy which is at least partially responsible for both the alveolar hypoventilation and the hypersomnia.