Acute changes in regional brain water content following experimental closed head injury

A Remington humane stunner was used to deliver blows to the skulls of anesthetized cats. The animals were sacrificed at 30 minutes or 1, 2, or 6 hours after trauma and selected for data collection on the basis of the following two categories of gross intracranial pathology: 1) unilateral contusion, with subarachnoid hemorrhage (SAH); or 2) SAH only. For selected cats, specific gravity was measured in 5- to 10-mg samples of uncontused tissue taken from coronal slices at the level of the frontoparietal suture. The regions tested included dorsal cerebral cortex, subcortical white matter, deep white matter, and caudate nucleus. Specific gravity data from injured animals were compared with those from similar areas in uninjured anesthetized cats to test for cerebral edema. At 30 minutes after head injury, contused hemispheres had significant edema of all tested except the caudate nucleus. Edema of the subcortical and deep white matter increased with time after the injury. Increase in water content of the cerebral cortex was transient and appeared unrelated to contusion. The caudate nucleus was edematous only at 6 hours, suggesting movement of fluid from the deep white matter compartment into the nucleus. The hemispheres opposite the contusion and those related to SAH had, with one exception, an absence of edema in the white matter and caudate nucleus, but a transient increase in water content of the cerebral cortex. These findings suggest that, in the presence of contusion, cerebral edema can contribute to brain swelling as early as 30 minutes after closed head trauma. In addition, a transient and minimal cortical edema, perhaps related to ischemia, occurred in all groups of hemispheres examined.