Differences in gross appearance and histopathology of the outer membrane of the subdural hematoma envelope over time: A respective case series and literature review

Chronic subdural hematoma (CSDH) is a common disorder among elderly males. The most common theory of its cause is a minor brain injury resulting in the rupture of a bridging vein. The outer membrane of subdural hematoma (SDH) evolves like cutaneous wound healing with different phases. This report aims to use a surgical microscope and an electron microscope to show the pathophysiological differences in the temporal flow of the outer membrane of SDH. This study retrospectively reviewed the cases of 6 patients who underwent craniotomy from 2016 to 2021 at the single center of Chonnam National University Hospital. These patients had a history of intracranial hematoma (ICH) at the surgical site on brain computed tomography (CT) before craniotomy. This study aimed to observe the morphological changes over time in the outer membrane of SDH and analyzed them through macroscopic and pathological findings. The outer membrane of SDH was confirmed in all six patients who underwent surgery, and macroscopic analysis was performed using an operating microscope. Three patients underwent pathological analysis through histological examination, and through this, the difference according to ICH occurrence and detection time was analyzed. This study suggests that the outer membrane of SDH contains inflammatory and collagen cells in the early stages and thickens over time. This healing response is similar to cutaneous wound healing.