EXPERIMENTAL STUDY ON HEMORRHAGE IN THE BRAIN STEM INDUCED BY AN INTRACRANIAL SPACE OCCUPYING LESION

Increased intracranial pressure was experimentally produced in dogs by inserting a rubber balloon epidurally in the left temporal region and then inflating the balloon with water. The animals were killed after a set interval and the hemorrhagic lesion in the brain stem examined in detail. 1. The hemorrhagic lesions in the brain stem could be microscopically classified into three types; arterial, venous and capillary. Massive hemorrhagic lesion was also observed in some animals. 2. Arterial hemorrhage was distributed mostly in the area supplied by the thalamo-perforating artery in the diencephalon and in the area supplied by the paramedian branches of the basilar artery in the lower brain stem. Venous hemorrhage was found mostly in the region of the terminal vein and basal vein in the diencephalon and in the region of the basilar vein in the lower brain stem. Capillary hemorrhage was extensive and the distribution corresponded approximately with that of venous hemorrhage but also in part with that of arterial lesions. 3. A relation was apparent between the hemorrhagic lesion in the brain stem and the amount of water instilled into the rubber balloon, which could be correlated to intracranial pressure. Capillary hemorrhage was observed in most cases in which over 3.5 ml of water was instilled. With instillation of 4.0 ml of water, all types of hemorrhage were observed profusely but venos hemorrhage predominated. With instillation of more than 4.5 ml of water, arterial hemorrhage was dominant. 4. The relation between the hemorrhagic lesions and the survival time after procedure was studied in the animals which had died naturally. Capillary hemorrhage was observed in almost all the animals irregardless of the survival time. Both arterial and venous hemorrhage were observed abundantly in animals which survived for over 10 hours. Arterial hemorrhage, in particular, was dominant in the cases which died within 12 hours and the venous type was dominant in the case surviving over 12 hours.