Vasospasm after subarachnoid hemorrhage - Interest in diffusion-weighted MR imaging

Background and Purpose-Vasospasm secondary to subarachnoid hemorrhage (SAH) is responsible for severe ischemic complications. Although effective, angi oplasty must be performed at a very early stage to produce any clinical rec overy. Diagnostic investigations to assess arterial narrowing (transcranial Doppler, angiography) or cerebral perfusion (xenon CT, single-photon emiss ion CT) do not provide evidence of the extent of parenchymal ischemia. In s troke, diffusion-weighted MR imaging (DWI) appears to be the most sensitive procedure to detect cerebral ischemia. We studied asymptomatic vasospasm i n patients with aneurysmal SAH to assess whether DWI provides predictive ma rkers of silent ischemic lesions and/or progression toward symptomatic isch emia. Methods-Seven asymptomatic vasospasm patients (average blood velocity rates > 120 cm/s), 3 patients with symptomatic vasospasm, and 4 patients with SA H but without vasospasm were studied at regular intervals by DWI, and their apparent diffusion coefficients (ADCs) were calculated. Results-All patients with vasospasm including those without symptoms presen ted abnormalities on DWI with a reduction of the ADC prevalently in the whi te matter. No such abnormalities were observed in patients without vasospas m. The abnormalities on DWI resolved completely in 4 of the 7 patients, wit h no parenchymal lesion. Resolution was partial in 3 patients whose white m atter still presented residual round, focal ischemic lesions. Conclusions-Being able to correlate abnormalities on DWI with parenchymal i nvolvement in asymptomatic patients would be of considerable clinical signi ficance. It is hoped that larger studies will be undertaken to determine wh ether the ADC has a reversibility threshold, because this would facilitate patient management.