Abstract
Obstructive sleep apnea syndrome (OSA) and restless legs syndrome (RLS) with periodic limb movement during sleep (PLMS) are two sleep disorders characterized by repetitive respiratory or movement events associated with cortical arousals. We compared the cerebral hemodynamic changes linked to periodic apneas/hypopneas with arousals (AHA) in four OSA-patients with periodic limb movements (PLMA) with arousals in four patients with RLS-PLMS using near-infrared spectroscopy (NIRS). AHA induced homogenous pattern of periodic fluctuations in oxygenated (HbO2) and deoxygenated (HHb) hemoglobin, i.e., the decrease of HbO2 was accompanied by an increase of HHb during the respiratory event and resolved to reverse pattern when cortical arousal started. Blood volume (BV) showed the same pattern as HHb but with relative smaller amplitude in most of the AHA events.These changing patterns were significant as Wilcoxon signed-rank tests gave p < 0.001 when comparing the area under the curve of these hemodynamic parameters to zero. By contrast, in PLMA limb movements induced periodic increments in HbO2 and BV (Wilcoxon signed-rank tests, p < 0.001), but HHb changed more heterogeneously even during the events coming from the same patient. Heart rate (HR) also showed different patterns between AHA and PLMA. It significantly decreased during the respiratory event (Wilcoxon signed-rank test, p < 0.001) and then increased after the occurrence of cortical arousal (Wilcoxon signed-rank test, p < 0.001); while in PLMA HR first increased preceding the occurrence of cortical arousal (Wilcoxon signed-rank test, p < 0.001) and then decreased. The results of this preliminary study show that both AHA and PLMA induce changes in cerebral hemodynamics. The occurrence of cortical arousal is accompanied by increased HR in both events, but by different BV changes (i.e., decreased/increased BV in AHA/PLMA, respectively). HR changes may partially account for the increased cerebral hemodynamics during PLMA; whereas in AHA probable vasodilatation mediated by hypoxia/hypercapnia is more crucial for the post-arousal hemodynamics. The differences between changes of cerebral hemodynamics and HR may indicate different pathological mechanisms behind these two sleep disorder events.
Highlights
Obstructive sleep apnea syndrome (OSA) and restless legs syndrome (RLS) with periodic limb movement during sleep (PLMS) are two of the most common sleep disorders
Our results of different cerebral hemodynamic patterns in Periodic Limb Movement with Arousal (PLMA) and Apnea/Hypopnea with Arousal (AHA) challenge the hypothesis of common generator of these two events and point to different underlying mechanisms
We propose that Heart Rate (HR) changes may partly account for cerebral Blood volume (BV) changes in PLMA, but not for the ones in AHA
Summary
Obstructive sleep apnea syndrome (OSA) and restless legs syndrome (RLS) with periodic limb movement during sleep (PLMS) are two of the most common sleep disorders. The main features of PLMS are periodic, short-lasting and involuntary movements of the limbs during sleep, usually occurring in the legs and often associated with a partial arousal or awakening (Manconi et al, 2014). Patients with PLMS are usually unaware of their nocturnal movements and associated sleep disruption. OSA and PLMS usually share common features, such as the repetitive occurrence of respiratory and limb movement events (apnea phenomenon is characterized by a periodicity of 30–40 s, and PLMS’ periodicity is 20–40 s), both are variably associated with cortical electroencephalogram (EEG) changes (i.e., cortical arousals; Ferrillo et al, 2004; Kohler and Stradling, 2010). PLMS is a common finding in patients with OSA
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