Persistent trigeminal artery variants detected by MR angiography

Persistent trigeminal artery (PTA) variants are cerebellar arteries that or iginate directly from the precavernous portion of the internal carotid arte ry (ICA). The goal of our study was to determine the incidence and MR angio graphic features of PTA variants. Between April 1996 and September 1999, 52 3 cranial MR angiographies were performed at our institution. Most of the p atients examined had or were suspected of having cerebrovascular disease. W e retrospectively reviewed these 523 MR angiograms. A 1.5-T scanner was use d in all studies, and maximum intensity projection (MIP) images obtained us ing the three-dimensional time-of-flight (3D TOF) technique were displayed stereoscopically. Four PTA variants were detected on MR angiograms, at a ra te of 0.76%. At least three of the four PTA variants were anterior inferior cerebellar arteries (AICAs), small tortuous arteries arising from the prec avernous portions of the ICAs and taking a posterior course. Although the c linical significance is not great, we found a relatively high incidence of PTA variants on MR angiograms. We stress that knowledge and recognition of these anomalous cerebellar arteries are useful and important in the interpr etation of cranial MR angiograms.