MR in acute stroke: How useful for the clinician?

Background. Magnetic resonance (MR) imaging is increasingly indicated as the most informative instrumental investigation in acute stroke. We summarize our initial experience in the use of multiparametric MR in stroke patients investigated within the first few hours of onset. Method. Our imaging protocol includes T2-FLAIR, DWI, pre-contrast T1, MRA, PWI and post-contrast T1, all in the transverse plane. The complete protocol requires a total scanning time of about 20 min. Most of our patients also undergo an emergency non-enhanced CT on admission. Results. Up to now, we have studied 30 stroke patients within 12 h of onset. None received thrombolytic therapy. In all patients with acute ischemic stroke, DWI showed focal changes that allowed the diagnosis of lesion location and extent. DWI was also positive in patients with unremarkable CT. The pattern of cerebral blood volume (CBV), mean transit time (MTT), time-to-peak (TTP), and cerebral blood flow (CBF) correlated with the presence of arterial (mainly MCA) occlusion at MRA. Patients with initial DWI abnormalities always had a visible infarct on follow-up T2-FLAIR images. Baseline hemodynamic abnormalities helped predict the evolution of the infarct. Acute parenchymal hemorrhage and dural sinus thrombosis could also be diagnosed with MR. In these cases, susceptibility-based T2*-weighted sequences proved especially sensitive to the presence of bleeding. Conclusions. Multiparametric MR is an accurate diagnostic tool in acute stroke and in the clinical setting appears superior to conventional CT as it more often detects focal lesions and provide useful predictive parameters. With these characteristics MR seems to be the investigation of choice in selecting patients for specific treatment, including surgical or pharmacological reperfusion.