The morphology of the outer and inner membranes of traumatic chronic
subdural hematomas (CSDHs) surgically removed from eight patients was
investigated by scanning electron microscopy (SEM). Hematomas were divided
into three groups based on time that had passed from the initiation of
trauma to surgery. Structure of the CSDHs showed gradual morphological
changes of the developing hematoma capsule. They initially included
angiogenic and aseptic inflammatory reactions followed by progressive
involvement of fibroblasts—proliferating and producing collagen
fibrils. Numerous capillaries suggesting formation of new blood vessels
were observed mainly in young hematomas removed between 15 and 21 days
after trauma. In “older” hematomas (40 days after trauma),
more numerous capillaries and thin-walled sinusoids were accompanied by
patent, larger diameter blood vessels. Within the fibrotic outer membrane
of the “oldest” hematoma capsules (60 or more days after
trauma), especially in the area over the hematoma cavity, blood vessels
were frequently occluded by clots. The results suggest dynamic changes in
cellular and vascular organization of traumatic CSDH capsules paralleling
the progression in hematoma age.