Glymphatic System Dysfunction in Central Nervous System Diseases.

In this review, we synthesize mechanistic and clinical evidence for glymphatic impairment in acute brain injury (ischemic and hemorrhagic stroke, traumatic brain injury) and chronic neurological disorders (Alzheimer's disease, Parkinson's disease, cerebral small vessel disease, multiple sclerosis, idiopathic normal pressure hydrocephalus, idiopathic intracranial hypertension, epilepsy, and headache disorders). Major mechanisms include (i) aquaporin-4 (AQP4) depolarization/mislocalization at astrocytic endfeet, reducing perivascular water transport; (ii) perivascular space compression or obstruction from cytotoxic/vasogenic edema, blood-derived products, protein aggregates, or altered extracellular matrix; (iii) loss of arterial pulsatility and vascular stiffening, weakening the driving forces for convective exchange; (iv) blood-brain barrier disruption and neuroinflammation, which remodel perivascular architecture and amplify clearance failure; and (v) sleep and autonomic dysregulation, including altered noradrenergic tone, which suppresses glymphatic activity during periods when clearance is normally maximal. Clinically, glymphatic dysfunction can be probed using diffusion tensor imaging-analysis along the perivascular space (DTI-ALPS), contrast-enhanced MRI approaches, and structural surrogates such as enlarged perivascular spaces, with emerging associations to cognition, mood, and disease severity. Finally, we discuss translational strategies aimed at restoring clearance, including sleep/circadian optimization, vascular risk control, anti-inflammatory approaches, AQP4- and TRPV4-oriented targets, and neuromodulation. Mechanism-guided, standardized imaging and longitudinal interventional studies are needed to establish glymphatic biomarkers as actionable therapeutic and prognostic tools.