Comparative analysis of experimental epidural and subarachnoid bleedings in dogs.

The difference in the course and the lethal mechanism between intracranial, subarachnoid and epidural bleedings was studied in a dog model under varying conditions. Subarachnoid bleedings were usually shortlasting, self-restricting, and generally survivable. The epidural bleedings differed quantitatively and qualitatively from the subarachnoid bleedings in being larger and having a longer duration. The difference seems related mainly to the development of an arterio-venous shunt in the epidural space during the bleeding. It is suggested that the epidural arterio-venous shunt may be of importance for the course and the lethal mechanism in epidural bleeding.