Cerebrospinal fluid egress to human parasagittal dura and the impact of sleep deprivation.

Emerging evidence suggests that the glymphatic system and meningeal lymphatic vessels are instrumental for clearance of toxic metabolites from the brain. Animal and human studies suggest that glymphatic circulation is up-regulated during sleep. Meningeal lymphatic clearance may be more efficient in the wake state, as shown in rodents. We have previously shown clearance of cerebrospinal fluid directly from the subarachnoid space to the parasagittal dura, which harbors meningeal lymphatic vessels. Hence, assessing molecular clearance from parasagittal dura provides an opportunity to decipher the role of sleep/sleep deprivation in human lymphatic clearance function. In this study, we applied magnetic resonance imaging to explore whether sleep deprivation modifies molecular clearance from human parasagittal dura, utilizing an intrathecal magnetic resonance imaging contrast agent as tracer. We hypothesized that tracer enhancement in parasagittal dura would differ after sleep deprivation. One group of individuals (n = 7) underwent one night's total sleep deprivation while a control group (n = 9) was allowed unrestricted sleep. There were no sleep restrictions after the 24-hour time point. After one night of sleep deprivation (at 24 h), we found neither evidence for altered tracer enrichment in the parasagittal dura, nor after a day of unrestricted sleep (at 48 h). The hypothesis of altered molecular egress to parasagittal dura after sleep deprivation was not supported by our data. Further studies are required to determine the role of sleep for molecular clearance from cerebrospinal fluid to meningeal lymphatic vessels in humans.