Diffusion-weighted MR imaging of global cerebral anoxia

BACKGROUND AND PURPOSE: Diffuse cerebral anoxia is a devastating event, and its acute findings, as revealed by conventional MR imaging and CT scanning , may be subtle. We analyzed diffusion-weighted and conventional MR images of patients with diffuse cerebral anoxia to determine their usefulness in e stablishing the diagnosis during the acute period and in determining the ag e of insult. METHODS: We reviewed 11 MR imaging studies of 10 patients who had experienc ed prolonged cardiac arrest. All of the patients underwent echo-planar diff usion-weighted imaging with low- and high-strength B values and multiplanar unenhanced MR imaging. We considered bright areas on the high-strength dif fusion-weighted images to be abnormal when compared with low-strength image s. Special attention was given to the cortex, basal ganglia, thalami, hippo campi, cerebellum, and white matter. Conventional MR studies also were revi ewed, and abnormalities noted. The medical records of all of the patients w ere reviewed. RESULTS: Four patients who underwent imaging during the acute period (<24 h ours) had bright basal gauglia (n = 2), bright cerebellum (n = 3), and brig ht cortex (n = 1) shown on their diffusion-weighted images. For these patie nts, conventional MR images showed questionable increased T2-weighted signa l intensity in the basal ganglia (n = 1), and the results of two studies we re judged to be normal. During the early subacute period (24 hours-13 days) , four patients were studied, and were determined to have an abnormal corte x (n = 3) and basal ganglia (n = 2). For two of these patients, conventiona l MR images showed similar abnormalities, and the results of one study were normal. For two patients who underwent imaging during the late subacute pe riod (14-20 days), diffusion-weighted images showed abnormalities mostly co nfined to white matter. Two patients who underwent imaging during the chron ic phase (>21 days) had normal results of their diffusion-weighted imaging and one had evidence of laminar necrosis revealed by conventional MR imagin g. CONCLUSION: During the acute period, high-strength diffusion-weighted image s showed the abnormal basal ganglia, cerebellum, and cortex to a better ext ent than did conventional MR images. During the early subacute period, gray matter abnormalities were seen on diffusion-weighted images. During the la te subacute period, diffusion-weighted images showed mostly white matter ab normalities. During the chronic stage, the results of diffusion-weighted im aging were normal. Our findings suggest that diffusion-weighted images are helpful for evaluating and dating diffuse cerebral anoxia, and therefore ai d in the determination of prognosis and management of these patients.