ACUTE SUBDURAL-HEMATOMA - IS THE BLOOD ITSELF TOXIC

Recently developed rodent models of acute subdural hematoma have shown an associated large area of infarction underlying the clot. Excitotox ic processes have been postulated to play an important role in the ext ensive cell death seen with these models. However, whether increased p ressure, vasoactive effects, or toxicity of the blood itself is respon sible for initiating or sustaining these processes remains unclear. To study the effect of blood itself, an opaque layer of autologous clot was placed on the widely exposed parietal cortex of 15 Long-Evans rats and left in place for 72 h. In control animals the cortical surface w as exposed but no blood was placed and contact with blood products was carefully limited. These animals were compared to a group in whom blo od was injected into the closed subdural space. Histologic analysis sh owed that the majority of the cortex in both control and experimental animals in the open cranial model group appeared normal. Scattered sma ll, discrete hemorrhagic lesions on the cortical surface of both contr ol and experimental animals were seen, which had the appearance of foc al mechanical trauma or vessel avulsion. There was no significant diff erence in average volume of lesions between experimental and control a nimals (9.1 versus 9.7 mm(3), p = 0.85). No areas of infarction or sel ective neuronal loss were seen. In comparison, animals in which blood was injected into the subdural space had significantly larger lesions underlying clot, averaging 133.6 mm(3) in volume (p < 0.0003). Blood i n prolonged contact with the cortical surface in the absence of increa sed pressure, ischemia, or other insult is insufficient to cause under lying infarction like that seen when a similar volume of blood is inje cted into the closed subdural space.