Sleep related breathing patterns in patients with spinal muscular atrophy

A clinical and polygraphic study of nocturnal sleep was performed in 8 (4 males, 4 females; age range 10-37 years) patients with spinal muscular atrophy, whose baseline respiratory function assessment during wakefulness showed restrictive ventilatory syndrome but blood-gas tension within normal limits. No patient reported any significant sleep complaint suggestive of sleep-disordered breathing. However, in 4 patients HbSaO2 desaturations below 90% (HbSaO2 nadir 68%) were detected during nocturnal polysomnography. The HbSaO2 desaturations occurred during brief central apneas or hypopneas, mainly during REM sleep, the apnoea hypopnea index being within normal limits in all cases. The data suggest that nocturnal polysomnography can detect otherwise clinically silent hypoxemia in SMA patients without any predisposing factor to sleep-disordered breathing other than their illness and still showing normal blood-gas tensions during wakefulness. Further studies are needed to determine the long-term evolution and the prognostic significance of nocturnal hypoxemia in these patients.