MR-IMAGING OF MIDDLE CEREBRAL-ARTERY STENOSIS AND OCCLUSION - VALUE OF MR-ANGIOGRAPHY

PURPOSE: To investigate the effectiveness of MR angiography in conjunc tion with spin-echo imaging for evaluating vascular patency in patient s with middle cerebral artery (MCA) stenosis or occlusion. METHODS: Se ven patients with MCA stenosis or occlusion, verified with contrast an giography in five and correlated with transcranial Doppler sonography in two, were examined using two-dimensional and/or three-dimensional t ime-of-flight MR angiographic techniques as well as conventional spin- echo imaging. RESULTS: Of the seven patients, six demonstrated basal g anglionic and/or cortical infarct in the MCA territory. Except one cas e with minimal stenosis immediately distal to the MCA origin, all six cases with either severe stenosis or occlusion of the main trunk of th e MCA showed the absence of normal flow voids using spin-echo imaging in the sylvian fissure on the affected side. However, it was not possi ble to discriminate between stenosis and occlusion. Although different mechanisms (ie, flow-induced spin dephasing for the 2-D technique and progressive spin saturation for the 3-D technique) were predominantly responsible for the loss of signal through the area of stenosis, both the 2-D and 3-D MR angiograms clearly depicted the compromised flow o f the MCA: a focal discontinuity with decreased vessel caliber corresp onded to stenosis, and nonvisualization of distal MCA branches represe nted occlusion. CONCLUSION: Either 2-D or 3-D time-of-flight MR angiog raphy is a useful adjunct to conventional parenchymal spin-echo imagin g for evaluating vascular patency in patients with MCA stenosis or occ lusion, although it is important to recognize that each technique has a different basis for the loss of signal through the area of stenosis.