MR angiography in internal carotid artery dissection: improvement of diagnosis by selective demonstration of the intramural haematoma.

We studied eight consecutive patients with clinical and intra-arterial angiographic (DSA) diagnosis of internal carotid artery (ICA) dissection to analyse the accuracy of MRA in dissections, using a new technique with presaturation pulses. Spin-echo images of the head were followed by three-dimensional time-of-flight (TOF) MRA at the site of the dissection, with and without a special caudal saturation pulse in addition to the cranial one. The accuracy of MRA was assessed in 64 segments of 16 ICA, all examined with DSA and MRA. High-signal intramural haematoma in the ICA at the level of the dissection was observed in all patients either on the maximal-intensity projection (MIP) reconstructions or on the partitions with this presaturation pulse technique. MRA had a sensitivity to detect dissected vessels of 100%. Specificity for vessels correctly identified as not having a lesion was also 100%. There was good correlation between DSA and MRA in demonstrating the site of the dissected ICA segment and the degree of stenosis. In only two cases was there overestimation of the degree of stenosis on the MIP reconstructions of the 3-D MRA.