Misa Trieu, Ajith Thomas
Chronic subdural hematoma (CSDH) is an increasingly common disorder characterized by persistent accumulation of blood products and inflammatory exudate within the dural border cell (DBC) layer. Its pathogenesis represents a self-sustaining cycle of inflammation, pathological angiogenesis, and impaired resolution. Injury of the head, which may be traumatic or nontraumatic, initiates cleavage of the DBC layer, leading to fibroproliferative membrane formation mediated by collagen synthesis and TGF-β1/SMAD signaling. The resulting outer membrane develops fragile neovasculature, driven primarily by vascular endothelial growth factor, facilitating recurrent microhemorrhage and fibrinolysis perpetuating hematoma expansion. Chronic inflammation sustains disease progression through macrophage polarization, cytokine release, and increased vascular permeability, processes amplified by age-related immune dysregulation and hypoxia-induced factor-1alpha signaling. Impaired tissue repair due to metabolic deficits further limits resolution. Concurrent dysfunction of meningeal lymphatic drainage and fibrotic arachnoid granulations compromises clearance of blood degradation products and inflammatory mediators, while matrix remodeling and cerebrospinal fluid ingress contribute to hematoma persistence. This narrative review presents a pathophysiologic framework highlighting CSDH as a dynamic inflammatory-angiogenic disorder. Pharmacological strategies targeting inflammation, angiogenesis, fibrinolysis, hypoxia, and matrix remodeling hold potential as complements or alternatives to established treatments, including surgical drainage and middle meningeal artery embolization. As the burden of CSDH on healthcare systems rises, translational research and controlled clinical trials will be critical to developing mechanism-driven, multimodal management paradigms.