Abstract
Although there have been numerous clinical and experimental studies of the etiology and clinical features of chronic subdural hematoma, certain details remain obscure. For instance, it is unknown whether the neomembranes (outer membranes) are peculiar to chronic subdural hematomas or whether they are caused by a general inflammatory reaction. The pathological features of these neomembranes were studied in relation to the clinical presentation in 46 patients with chronic subdural hematoma who underwent surgery at Nagoya City University. There were 34 males and 12 females, and their ages ranged from 26 to 84 years. Since attention has recently been focused on eosinophilic infiltration in the outer membranes, the patients were divided into two groups according to whether eosinophilic infiltration was extensive (Group A) or negligible (Group B). There was no significant sex difference between the groups; 47% of the males and 42% of the females were in Group A. There were no significant correlations between the extent of eosinophilic infiltration and either age or the interval from trauma to surgery. Intramembranous hemorrhage was observed more frequently in Group B. It was not possible to differentiate the two groups by computed tomography (CT) alone, as the preoperative hematoma densities were similarly distributed between them on CT scans. There was no correlation between the preoperative maximal thickness of the hematoma cavity and the extent of eosinophilic infiltration. The serum eosinophil counts were normal in all patients evaluated. Patients who showed no clinical improvement following surgery and/or required a second operation all belonged to Group B.
Some authors claim that eosinophils participate in the absorption of hematomas and the formation of granulation tissue, while others assert that eosinophilic infiltration can cause rebleeding. In the present study there was a higher incidence of intramembranous hemorrhage and a less favorable response to surgery in Group B than in Group A, which suggests that eosinophilic infiltration plays a key role in the formation of granulation tissue and the prevention of rebleeding.
