ABNORMALITIES OF THE POSTERIOR INFERIOR CEREBELLAR ARTERY - MR-IMAGING FINDINGS

The purpose of this essay is to review the normal MR appearance of the posterior inferior cerebellar artery (PICA) and to illustrate the MR findings of representative PICA abnormalities. Because of beam-hardeni ng artifacts, the lower posterior fossa is difficult to evaluate with CT. MR imaging is not hampered by these artifacts. Moreover, the super b sensitivity of MR and its multiplanar imaging capability permit exce llent diagnostic accuracy in this region. The PICA is well suited for evaluation on routine MR images, particularly because of the inherent contrast (signal void) of large arteries due to rapid flow. MR imaging has greatly improved our ability to noninvasively diagnose abnormalit ies of cerebral blood vessels and their resultant manifestations. Some of the diseases that affect the PICA include neoplasms, aneurysms, ar teriovenous malformations, and occlusions. The MR images in this essay illustrate the normal appearance of the PICA, as well as these pathol ogic features. T1-weighted (e.g., 600/15 [TR/TE]), proton density-weig hted (e.g., 2000/20), and T2-weighted (e.g., 2400/80) MR images were o btained in axial, sagittal, and coronal planes. The PICA can be evalua ted with MR angiography also, although the relatively small size and t ortuosity of the artery may preclude adequate visualization.