The Role of the Brain-lymphatic Axis in Traumatic Brain Injury-associated Cognitive Impairment: From Glymphatic System Clearance Dysfunction to Peripheral Lymphatic Stasis

Traumatic brain injury (TBI)-associated cognitive impairment is highly prevalent, severely impacting patients’ daily life and social functioning, with its mechanisms incompletely understood. Globally, TBI affects over 69 million people annually, and post-TBI cognitive impairment may last for years, or even a lifetime, imposing heavy burdens on patients’ families. The brain-lymphatic axis (glymphatic + peripheral lymphatic systems, especially meningeal vessels) has gained attention: glymphatic dysfunction (dependent on astrocyte endfeet Aquaporin-4 polarization, key for clearing β-amyloid and other wastes) causes metabolic waste accumulation and neuroinflammation, while peripheral lymphatic stasis worsens cognitive decline. This review aims to summarize their roles, dissect mechanisms, and outline therapies. The review found that most current studies explore the glymphatic system and the peripheral lymphatic system in isolation, lacking understanding of their dynamic interplay (e.g., bidirectional inflammatory factor transmission, immune cell migration, synergistic dysfunction); longitudinal studies that track axis changes across TBI stages (acute, subacute, chronic) are scarce; diagnostic tools are insufficient (non-invasive biomarkers lack large-scale clinical validation, and imaging has limited clinical use); and existing therapeutic strategies mostly target single subsystems, with few combined interventions for the whole axis. In conclusion, this review highlights critical gaps in current knowledge and proposes integrated, axis-targeted approaches as a promising direction for future research and therapeutic development.