Impact of acute administration of sodium oxybate on nocturnal sleep polysomnography and on multiple sleep latency test in narcolepsy with cataplexy

To analyze the acute effects of sodium oxybate (SO) on polysomnographic night-time recordings (PSG) and multiple sleep latency test (MSLT) on patients with narcolepsy with cataplexy (NC).Sixteen NC adult patients were recruited, together with 16 normal controls. Two consecutive PSG followed by two MSLT sessions were carried out, before and during the first night of SO assumption, respectively.The administration of SO was followed by a significant decrease in number of stage shifts and awakenings, wakefulness after sleep onset, and percentage of sleep stage 1. Sleep efficiency and slow wave sleep percentage increased. REM latency decreased significantly from 73 to 12 min. Cyclic alternating pattern (CAP) rate remained unchanged but the percentage of CAP A3 subtypes decreased. The number of CAP A3 subtypes per hour of NREM sleep decreased significantly, whereas that of A1 remained unchanged. The duration of A1 and A3 subtypes was slightly increased. Chin muscle tone was not modified by SO as well as periodic leg movements during sleep, but their periodicity index decreased, becoming similar to that of controls. MSLT sleep latency also significantly improved after SO intake.The administration of SO in NC patients is followed by immediate important and complex effects on PSG parameters and MSLT, including an evident (over)increase in slow wave sleep, which does not display a physiological microstructure, a moderate decrease in periodic and isolated LMs, possibly mediated by a disinhibited dopaminergic neuronal activity, and an improvement on daytime mean sleep latency at the MSLT.