Diffusion- and Perfusion-Weighted Imaging in Vasospasm After Subarachnoid Hemorrhage

Abstract

Background and Purpose-Better measures of cerebral tissue perfusion and earlier detection of ischemic injury are needed to guide therapy in subarachnoid hemorrhage (SAH) patients with vasospasm. We sought to identify tissue ischemia and early ischemic injury with combined diffusion-weighted (DW) and hemodynamically weighted (HW) MRI in patients with vasospasm after SAH. Methods-Combined DW and HW imaging was used to study 6 patients with clinical and angiographic vasospasm, 1 patient without clinical signs of vasospasm but with severe angiographic vasospasm, and 1 patient without angiographic spasm. Analysis of the passage of an intravenous contrast bolus through brain was used to construct multislice maps of relative cerebral blood volume (rCBV), relative cerebral blood flow (rCBF), and tissue mean transit time (tMTT). We hypothesize that large HW imaging (HWI) abnormalities would be present in treated patients at the time they develop neurological deficit due to vasospasm without matching DW imaging (DWI) abnormalities. Results-Small, sometimes multiple, ischemic lesions on DWI were seen encircled by a large area of decreased rCBF and increased tMTT in all patients with symptomatic vasospasm. Decreases in rCBV were not prominent. MRI hemodynamic abnormalities occurred in regions supplied by vessels with angiographic vasospasm or in their watershed territories. All patients with neurological deficit showed an area of abnormal tMTT much larger than the area of DWI abnormality. MRI images were normal in the asymptomatic patient with angiographic vasospasm and the patient with normal angiogram and no clinical signs of vasospasm. Conclusions-We

Diffusion-Perfusion Mismatch in Symptomatic Vasospasm After Subarachnoid Hemorrhage

“…24) Another study of perfusion-weighted imaging with MTT, CBV, and TTP was likely to detect excessive increases in MTT or TTP, because the space resolution of perfusion-weighted imaging cannot measure changes of circulation in a very small area. 13) The present method could detect the diffusionperfusion mismatch clearly in a relatively large area matched to the clinical symptoms, based on quantitative CBF measurement by perfusion-weighted imaging which was confirmed by comparing with CBF measurements by SPECT on the same day.…”

Cerebral perfusion imaging in vasospasm

“…37 In contrast, in patients with post-SAH vasospasm, a less severe decrease in relative CBF with preserved relative CBV was found to be the predominant abnormality. 33 In one study, large areas of brain with decreased relative CBF and increased mean transit time were seen on perfusion-weighted MR imaging in all patients with clinically symptomatic vasospasm, and the re-…”

“…23 Recently, the use of perfusion-weighted MR imaging in evaluating patients with post-SAH vasospasm was examined. 33 Results in patients with vasospasm show that diffusion-weighted MR imaging can be used to detect small regions of early ischemic injury within large regions of abnormal relative CBF and mean transit time. Widespread decreases in relative CBF and mean transit time occurred in each patient throughout regions supplied by vessels with angiographically demonstrated vasospasm.…”

3.0-t diffusion images after clipping of middle cerebral artery aneurysm.

“…Although AC is performed to decrease the risk of subarachnoid hemorrhage (SAH), these procedures can sometimes cause temporary or permanent neurological deficits (10,13,24,26,36). Most neurological complications that occur during or immediately after AC are reported (3,17,20,23,24,25,36) to result from cerebral ischemia caused by AC or temporary parent artery occlusion.…”