The meninges form a highly specialized barrier and immune interface that protects the central nervous system (CNS), regulates cerebrospinal fluid (CSF) dynamics, and coordinates communication between the CNS and the periphery. Each layer—dura mater, arachnoid mater and pia mater—possesses distinct structural, vascular and immunological features that collectively shape CNS homeostasis. A broad range of anatomical and molecular studies has revealed that meningeal compartments are far more heterogeneous and functionally complex than traditionally recognized, particularly with respect to their barrier architecture and immune interactions. In this review, we summarize current knowledge of meningeal structure and function, with a focus on barrier properties and immune-cell trafficking. We further discuss how meningeal dysfunction contributes to pathology in bacterial meningitis, multiple sclerosis and Alzheimer’s disease. Emerging evidence highlights the meninges as an active neuroimmune organ rather than a passive covering, critically influencing inflammation, solute clearance and disease progression. Understanding these mechanisms may open new therapeutic avenues targeting meningeal pathways across neurological disorders.
Joost et al. (Tue,) studied this question.