[Sleep apnea in well-controlled myasthenia gravis]

Polygraphic monitoring of the respiratory status during sleep provides a definitive test for the presence of the sleep apnea syndrome. This syndrome has been recognized in various kinds of neurological disorders. However, as far as we know, there have been no reports of describing the sleep apnea syndrome in myasthenia gravis (MG). We conducted overnight polygraphic sleep studies of 10 patients of clinically well-controlled MG.

We examined 10 patients of MG (4 men and 6 women). The subtypes of MG were IIA(1), IIB(8) and V(1) according to Osserman's criteria.

Six patients, with an average age of 47.8 and the average duration of 6.2 years, had polysomnographically obstructive and central types of sleep apnea, appearing longer than 10 seconds and more than 30 times in one night. Their mean Apnea Index (AI) was 14.6. The duration of mean apnea was 23.4 seconds and 99.0 times the average frequency. On the other hand, in four patients of MG, averaged age at 30.8 and for a 0.9-year duration, the sleep apnea syndrome was never seen. Therefore, the longest duration of MG tended to have the sleep apnea syndrome.

Six out of the 10 patients of MG had obstructive and central types of the sleep apnea syndrome. Since their respiratory functions examined in a daytime were normal and the physical findings concerned with MG were well controlled by medications, our findings of nocturnal sleep apnea might be indicative of a central cholinergic system disturbance in MG during sleep.