Diffusion- and perfusion-weighted imaging in vasospasm after subarachnoid hemorrhage

Background and Purpose-Better measures of cerebral tissue perfusion and ear lier detection of ischemic injury are needed to guide therapy in subarachno id hemorrhage (SAH) patients with vasospasm. We sought to identify tissue i schemia and early ischemic injury with combined diffusion-weighted (DW) and hemodynamically weighted (HW) MRT in patients with vasospasm after SAH, Methods-Combined DW and HW imaging was used to study 6 patients with clinic al and angiographic vasospasm, I patient without clinical signs of vasospas m but with severe angiographic vasospasm, and 1 patient without angiographi c spasm. Analysis of the passage of an intravenous contrast bolus through b rain was used to construct multislice maps of relative cerebral blood volum e (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 d ue to vasospasm without matching DW imaging (DWI) abnormalities. Results-Small, sometimes multiple, ischemic lesions on DWI were seen encirc led by a large area of decreased rCBF and increased tMTT in all patients wi th symptomatic vasospasm. Decreases in rCBV were not prominent. MRI hemodyn amic abnormalities occurred in regions supplied by vessels with angiographi c vasospasm or in their watershed territories. All patients with neurologic al deficit showed an area of abnormal tMTT much larger than the area of DWI abnormality. MRI images were normal in the asymptomatic patient with angio graphic vasospasm and the patient with normal angiogram and no clinical sig ns of vasospasm. Conclusions-We conclude that DW/HW MRI in symptomatic vasospasm can detect widespread changes in tissue hemodynamics that encircle early foci of ische mic injury. With additional study, the technique could become a useful tool in the clinical management of patients with SAH.