Diffusion-weighted magnetic resonance imaging in patients with subarachnoid hemorrhage

OBJECTIVE: To evaluate the occurrence and distribution of direct brain injury caused by acute subarachnoid hemorrhage (SAN) by the use of magnetic resonance imaging. METHODS: Computed tomography and magnetic resonance imaging, including diffusion-weighted imaging (DWI), were performed in 32 patients with SAH by use of a 1.5-T whole-body superconductive scanner equipped with an echo planar imaging system. In all cases, computed tomographic and magnetic resonance imaging scans were obtained at the time of admission, before angiography and surgical intervention. RESULTS: No abnormalities were revealed by DWI in any of the low-grade SAH patients. However, five (71%) of seven patients diagnosed as having poor-grade SAH (World Federation of Neurosurgical Societies Grades 4 and 5) displayed multiple, patchy focal abnormalities on DWI. Computed tomographic scans obtained at admission failed to clearly demonstrate all of the damaged areas of the brain that were visualized by DWI. These lesions were located in supratentorial cerebral parenchyma, but not in the thalamus, basal ganglia, or cerebellar hemisphere. These multiple widespread lesions exhibiting laminar involvement of the cerebral cortex were not associated with the site of the ruptured aneurysm. CONCLUSION: DWI revealed widespread multifocal lesions in the cerebral cortex of acute poor-grade SAH patients. DWI provides accurate images of all areas of brain damage directly attributable to SAH.