Comparison of cerebral blood flow and injury following intracerebral and subdural hematoma in the rat

Abstract

Subdural hematomas (SDH) can induce ischemia and neuronal damage in the underlying cortex. However, the extent to which intracerebral hematomas (ICH) produce reductions in cerebral blood flow (CBF) sufficient to cause ischemic damage is uncertain. Intracranial hemorrhage was induced by the injection of 100 or 200 μl of blood into the subdural space (SDH) or into the caudate nucleus (ICH) of the rat. CBF was measured using [ 14 C ]-iodoantipyrine autoradiography at 4 h. Brain damage was measured using 2,3,5-triphenyl tetrazolium chloride (TTC) staining at 24 h and brain edema was measured using the wet/dry weight method. Brain ion contents were measured at 24 h using a flame photometer and chloridometer. In the CBF studies, the volume of tissue perfused below the ischemic threshold (<20 ml/100 g/min) for SDH was 122±35 mm 3 (sham: 3.3±1.7 mm 3). Following ICH, there was a small volume of tissue perfused below the ischemic threshold 50±11 mm 3 (sham: 3.3±2.5 mm 3) but this volume corresponded closely to the volume of clot (71±5 mm 3). The extent of brain damage, measured by TTC staining, in the cerebral cortex correlated with the increasing volume of the subdural blood clot (sham: 9±3 mm 3; 200 μl: 81±19 mm 3; P<0.01). Conversely, minimal brain damage was detected following ICH. The injection of blood into the subdural space or into the brain parenchyma induced blood volume-dependent increases in brain water content at 24 h. Increases in brain water content after SDH, were confined to the cerebral cortex (sham: 0.1±0.1 g/g dry weight; 200 μl: 0.8±0.3 g/g dry weight; P<0.001). In contrast, increases in brain water content after ICH were predominantly in the subcortical region (sham: 0.1±0.1 g/g dry weight; 200 μl: 0.4±0.2 g/g dry weight; P<0.01). The present investigations demonstrate differences in CBF, brain injury and edema formation following SDH and ICH indicating that these conditions may require different therapeutic interventions.