Membrane formation in epidural and subperiosteal hematomas. Relationship with the neomembrane of chronic subdural hematomas

Abstract

Granulation tissues in four cases of chronic epidural hematoma, two of depressed fracture and two of ossified caput succenadeum were pathologically studied and compared with the neomembranes of subacute and chronic subdural hematomas. Five males and 3 females, ranging between 1 month and 51 years of age were examined. The elapsed time from trauma varied from 9 days to 3 months. Nine to fourteen day old epidural clots showed early granulation over the dural side. A zone of macrocapillaries and infiltration of the solid clots by endothelial cells and fibroblasts were seen microscopically. Three week old clots showed liquefaction and encapsulation. Microscopically, the sinusoidal channel layer and a zone of hemorrhage with widespread invasion of fibrovascular cells were noted. Next to the dura mater lay a layer of ossification. Small-sized brown-colored granulation tissues were found beneath the depressed bone fragments 13 to 21 days after trauma. Fibrous strands and residual clots with macrocapillaries were also seen. Ossified caput succenadeum contained bloody fluid with whitish and elastic capsules. Fibrous tissues intermingled with areas of macrocapillaries were microscopically noted. Thus, six cases of epidural clots, both large and small, induced a granulation reaction of the dura mater, similar to that found in subdural hematomas. Two cases of subperiosteal hematomas which had no contact with the dura showed a similar granulation reaction. Neomembrane formations in epidural hematoma as well as in subdural hematomas might be the result of the dura mater granulation reaction to blood clots, either solid or liquefied. Persistence of the subperiosteal hematoma would be analogous to Labadie's subcutaneously induced chronic subdural hematoma model in rats. Breakdown products of blood corpuscules such as hydroperoxides of prostaglandins were thought to induce these inflammatory reactions in the dura mater, as well as in other mesenchymal tissues.