Vasospasm after subarachnoid hemorrhage: Diagnosis with MR angiography

BACKGROUND AND PURPOSE: The possibility of treating intracranial vasospasm has increased the significance of its diagnosis and follow-up; however, so far, no ideal method is available. The goal of this study was to assess the accuracy of MR angiography versus intraarterial angiography (IA-DSA) in de tecting vasospasm, METHODS: The study included 42 patients with acute spontaneous subarachnoid hemorrhage (SAH), Serial MR angiograms (minimum, two per patient within 10 days after the event; total, 149) were obtained prospectively using a 3D t ime-of-flight technique covering the circle of Willis at 0.5 T. Forty-seven MR angiograms could be compared with intraarterial angiograms obtained wit hin 24 hours of MR angiography. Vascular narrowing on both studies was rate d consensually by two pairs of neuroradiologists using a scale from 0 (no n arrowing) to 3 (severe narrowing), Categories 0 and 1 were considered an ab sence of vasospasm and categories 2 and 3 a presence of vasospasm, RESULTS: Agreement between MR angiography and IA-DSA (assessed with weighte d kappa statistics) was substantial for the middle and anterior cerebral ar teries (MCA and ACA) but moderate for the internal carotid artery (ICA), Th e sensitivity, specificity, accuracy, and positive and negative predictive values of MR angiography for detecting patients with vasospasm were 92%, 98 %, 96%, 92%, and 98%, respectively. Considering each vessel separately, spe cificity was high for all locations (95-99%) and sensitivity was excellent for the ACA (100%) but poorer for the ICA (25%) and MCA (56%), CONCLUSION: MR angiography at 0.5 T is capable of identifying vasospasm aft er acute SAH but is less sensitive than IA-DSA for depicting vasospasm in t he ICA and MCA.