Subdural neomembranes, inner and outer: In this photomicrograph, stained with H&E, the dura lies at the top and an outer (middle of slide) and inner (bottom of slide) neomembrane occupy the remainder of the photomicrograph. The space occupied by the hematoma lies in between the outer and inner membranes. The continuity of these two membranes on the lower left side of the photomicrograph indicates that the section was taken at the margin of the subdural hematoma. Both the outer and inner neomembranes are formed from organizing elements that arise from the dura. The organizing tissue contains new blood vessels, proliferation of fibroblasts with collagen deposition, and scattered mononuclear cells. The outer and inner neomembranes serve to encapsulate the hematoma and partially organize it. Small subdural hematomas are probably completely organized and become static and asymptomatic. Larger subdural hematomas, however, present complications from gradual enlargement of the hematoma and compression of the underlying brain.