The Hypoxic-Glymphatic Axis: Deciphering the Failure of Perivascular Waste Clearance in Acute and Chronic Cerebral Oxygen Deprivation

Abstract The glymphatic system represents a critical brain-wide waste clearance pathway that operates through perivascular channels, facilitating the exchange of cerebrospinal fluid (CSF) and interstitial fluid (ISF). Cerebral hypoxia, whether acute or chronic, profoundly disrupts this clearance mechanism through multifactorial pathways including aquaporin-4 (AQP4) dysregulation, perivascular space compression, astrocytic end-feet swelling, and impaired cerebrovascular pulsatility. This review examines the mechanistic interplay between oxygen deprivation and glymphatic dysfunction, exploring how hypoxia-induced alterations in AQP4 polarization, extracellular matrix remodelling, and neurovascular unit integrity compromise waste clearance efficiency. We synthesize current evidence demonstrating that hypoxic conditions trigger a cascade of molecular and structural changes that impair both influx of CSF along periarterial spaces and efflux of ISF through perivenous pathways. Furthermore, we discuss how chronic hypoxic states, such as those observed in obstructive sleep apnea, high-altitude exposure, and cerebrovascular disease, establish sustained glymphatic impairment that may contribute to accelerated protein aggregation and neurodegeneration. Understanding the hypoxic-glymphatic axis provides critical insights into therapeutic strategies aimed at preserving brain waste clearance under conditions of oxygen insufficiency, with implications for stroke recovery, altitude medicine, and age-related cognitive decline. Keywords: Glymphatic system, cerebral hypoxia, aquaporin-4, perivascular clearance, neurovascular coupling, interstitial fluid dynamics