Criticality of neuronal avalanches in human sleep and their relationship with sleep macro- and micro-architecture.

Sleep plays a key role in preserving brain function, keeping brain networks in a state that ensures optimal computation. Empirical evidence indicates that this state is consistent with criticality, where scale-free neuronal avalanches emerge. However, the connection between sleep architecture and brain tuning to criticality remains poorly understood. Here, we characterize the critical behavior of avalanches and study their relationship with sleep macro- and micro-architectures, in particular, the cyclic alternating pattern (CAP). We show that avalanches exhibit robust scaling behaviors, with exponents obeying scaling relations consistent with the mean-field directed percolation universality class. We demonstrate that avalanche dynamics is modulated by the NREM-REM cycles and that, within NREM sleep, avalanche occurrence correlates with CAP activation phases-indicating a potential link between CAP and brain tuning to criticality. The results open new perspectives on the collective dynamics underlying CAP function, and on the relationship between sleep architecture, avalanches, and self-organization to criticality.

Sleep medicine: Practice, challenges and new frontiers.

Sleep medicine is an ambitious cross-disciplinary challenge, requiring the mutual integration between complementary specialists in order to build a solid framework. Although knowledge in the sleep field is growing impressively thanks to technical and brain imaging support and through detailed clinic-epidemiologic observations, several topics are still dominated by outdated paradigms. In this review we explore the main novelties and gaps in the field of sleep medicine, assess the commonest sleep disturbances, provide advices for routine clinical practice and offer alternative insights and perspectives on the future of sleep research.

Sleep macro- and micro-structure in autoimmune encephalitis: single case report from the subacute phase of the disease to the follow-up.

Sleep disorders are frequently described in autoimmune encephalitis (AE); however, data on sleep texture are fragmentary. We analyzed the polysomnography of a woman affected by AE, and we performed cyclic alternating pattern (CAP) scoring during the subacute phase of the disease and at follow-up. The first polysomnography showed deviations both at macro and microstructure levels, with a marked reduction of CAP rate compare to healthy sleepers (20.8% vs 33%). After 6-months sleep macrostructure improved, whilst CAP parameters remained abnormal. This is the first polysomnographic analysis, comprehensive of microstructural data, performed in AE. We briefly discuss the results.

Sleep features in Lymphangioleiomyomatosis and their relationship with disease severity: a pilot study.

Lymphangioleiomyomatosis (LAM) is a rare pulmonary disease characterized by progressive airflow limitation. We conducted a pilot trial to investigate the incidence of sleep disorders, sleep quality and their relationship with disease severity. We performed pulmonary function tests, blood gas analysis, overnight 12-channels polysomnography and clinical assessments in 15 consecutive LAM patients. For statistics, p values < 0.05 were considered significant. Sleep efficiency (SE) was inversely correlated with RV/TLC (p = 0.035) and positively with daytime SpO2 (p = 0.010) and PaO2 (p = 0.011). Three cases had obstructive sleep apnea (OSA); seven patients (46.7%) showed a REMOSA. AHIREM was correlated with FEV1% (r = 0.75, p = 0.003), TLC% (r = 0.57, p = 0.026), RV% (r = 0.8, p=<0.0001) and RV/TLC (r = 0.77, p = 0.001). No correlations were observed between anxiety/depression and SE, CAP rate, pulmonary function test variables and AHIREM (p > 0.05). four subjects had nocturnal hypoxia (T90 ≥ 1% of TST) showing lower values of DLCO%, daytime SpO2%, PaO2, FEV1% and a higher value of VR/TLC comparing with the subgroup with normal T90 (p < 0.05). This pilot study shows that sleep alterations could be frequent in LAM and associated to disease severity. Nocturnal hypoxemia and SE were related to lung function impairment. A dysregulation of sleep seems to involve exclusively REM phase, while NREM appears to be preserved. This phenomenon might be linked to the pathophysiology of disease: our study, even with the limits of the small sample size, showed that the presence of REMOSA is related to the disease severity, in particular to the degree of airflow limitation and hyperinflation. More studies are needed to assess this topic.

Commonalities and Differences in NREM Parasomnias and Sleep-Related Epilepsy: Is There a Continuum Between the Two Conditions?

Introduction: Differential diagnosis between disorders of arousal (DoA) and sleep-related hypermotor epilepsy (SHE) often represents a clinical challenge. The two conditions may be indistinguishable from a semiological point of view and the scalp video-polysomnography is often uninformative. Both disorders are associated with variable hypermotor manifestations ranging from major events to fragments of a hierarchical continuum of increasing intensity, complexity, and duration. Given their semiological overlap we decided to explore the sleep texture of DoA and SHE seeking for similarities and differences. Methods: We analyzed sleep macrostructure and CAP (cyclic alternating pattern) parameters in a cohort of 35 adult DoA patients, 40 SHE patients and 24 healthy sleepers, all recorded and scored in the same sleep laboratory. Nocturnal behavioral manifestations included minor motor events, paroxysmal arousals and major attacks in SHE, and simple, rising, or complex arousal movements in DoA. Results: Compared to healthy controls, DoA and SHE showed similar amounts of sleep efficiency, light sleep, deep sleep, REM sleep, CAP subtypes. Both groups also showed slow wave sleep fragmentation and an increased representation of stage N3 in the second part of the night. The only discriminating elements between the two conditions regarded sleep length (more reduced in DoA) and sleep instability (more elevated in SHE). In DoA recordings, all motor episodes arose from NREM sleep: 37% during light NREM stages and 63% during stage N3 (simple arousal movements: 94%). In SHE recordings, 57% of major attacks occurred during stage N3. Conclusions: So far, emphasis has been placed on the differentiation of sleep-related epilepsy and NREM arousal disorders. However, the impressive analogies between DoA and SHE suggest the existence of an underestimated continuum across the conditions, linked by increased levels of sleep instability, higher amounts of slow wave sleep and NREM/REM sleep imbalance. Sleep texture is extremely similar in the two conditions, although CAP metrics disclose quantitative differences. In particular, SHE patients show a higher arousal instability compared to DoA subjects. Given their clinical and epidemiological overlap, a common genetic background is also hypothesized. In such a perspective, we suggest that the consolidated dichotomy DoA vs. SHE should be reappraised.

Obstructive sleep apnea, cpap and COVID-19: a brief review.

Obstructive sleep apnea (OSA) is a broadly diffused curable chronic low-grade inflammatory disease sharing impressive clinical and pathogenetic features with Covid-19. Moreover, a potential role of OSA as a detrimental factor for Covid-19 severity has been hypothesized. Continuous positive airway pressure (CPAP) is the mainstay treatment for moderate-severe OSA, but the beneficial effects of ventilation strongly depend on medical expertise and on the patient's adherence and compliance. Although several papers have analyzed the overlaps and outcomes of OSA and Covid-19, limited attention has been dedicated to ventilatory adherence and management of  OSA cohorts exposed to Covid-19. We briefly review the literature data, pointing out the main risks and benefits of CPAP for OSA patients in the pandemic setting.