Neomembrane Formation Suggestive of an Organized Chronic Subdural Hematoma: An Incidental Cadaveric Finding.

Chronic subdural hematoma (cSDH) is an extra-axial lesion characterized by progressive organization and neomembrane formation. Although commonly diagnosed clinically, it may occasionally remain asymptomatic and be identified incidentally. During routine cadaveric dissection for undergraduate teaching, an unusual meningeal finding was observed in the cranial cavity of a 67-year-old male cadaver with no available clinical history. Gross examination revealed two thick, gray-white, well-organized membranous structures over the convexity of the left cerebral hemisphere, deep to the meningeal layer of the dura mater and superficial to the intact arachnoid mater, producing localized compression of the underlying parietal lobe. Histological evaluation demonstrated a multilayered neomembranous architecture with dense fibrocollagenous tissue, fibrovascular proliferation, organizing hematoma, and prominent neovascularization. This cadaveric gross and histological correlation highlights the structural organization of a lesion suggestive of an organized cSDH and may contribute to understanding the structural evolution of cSDH.