Waste clearance (WC) is an essential process for brain homeostasis, which is required for the proper and healthy functioning of all cerebrovascular and parenchymal brain cells. This review features our current understanding of brain WC, both within and external to the brain parenchyma. We describe the interplay of the blood-brain barrier (BBB), interstitial fluid (ISF), and perivascular spaces within the brain parenchyma for brain WC directly into the blood and/or cerebrospinal fluid (CSF). We also discuss the relevant role of the CSF and its exit routes in mediating WC. Recent discoveries of the glymphatic system and meningeal lymphatic vessels, and their relevance to brain WC are highlighted. Controversies related to brain WC research and potential future directions are presented.

The glymphatic system is a newly discovered waste drainage pathway in the brain; it plays an important role in many neurological diseases. Ongoing research utilizing various cerebrospinal fluid tracer infusions, either directly or indirectly into the brain parenchyma, is investigating clearance pathways by using distinct imaging techniques. In the present review, we discuss the role of the glymphatic system in various neurological diseases and efflux pathways of brain waste clearance based on current evidence and controversies. We mainly focus on new magnetic resonance imaging (MRI) modeling techniques, along with traditional computational modeling, for a better understanding of the glymphatic system function. Future sophisticated modeling techniques hold the potential to generate quantitative maps for glymphatic system parameters that could contribute to the diagnosis, monitoring, and prognosis of neurological diseases. The non-invasive nature of MRI may provide a safe and effective way to translate glymphatic system measurements from bench-to-bedside.

PRS Global Open • 2022 flaps. 30-day mortality following reconstruction was 3.9%. Median length-of-stay after initial debridement was 8 days (IQR5-15). Of patients with flaps, 54 (48%) required multiple debridements prior to closure, and 30 (27%) underwent reoperation after flap closure. Patients who needed only a single debridement were significantly less likely to have a complication requiring reoperation (N= 10/58 vs 20/54, 17% vs 37%, p=0.02), undergo a second flap (N=6/58 vs 17/54, 10% vs 32%, p<0.001) or, if plated, require removal of sternal plates (N=6/58 vs 11/22, 18% vs 50%, p=0.02). CONCLUSION:Although sternal dehiscence remains a complex challenge, an aggressive treatment algorithm, including debridement, flap closure and consideration of RSF, can achieve good long-term outcomes. In appropriately selected patients, RSF does not appear to increase the risk of reoperation. We hypothesize that earlier surgical intervention, before the development of systemic symptoms, may be associated with improved outcomes.