Postoperative oblique sagittal MR imaging of microvascular decompression for hemifacial spasm

Pre-operative and postoperative oblique sagittal gradient-echo magnetic res onance (MR) imaging was used to evaluate microvascular decompression of the facial nerves in 26 patients with hemifacial spasm. The pre-operative MR i mages were divided into two groups as follows: 22 images in Group I, clear imaging of a high-intensity line and/or spot at the root exit zone (REZ) of the facial nerve, and 3 in Group II, and unreliable image around the REZ. Surgery found that the causative vessel was the vertebral artery (VA) in 9 cases and the anterior inferior cerebellar artery (AICA) or the posterior i nferior cerebellar artery (PICA) in 13 cases in Group I. and the AICA or th e PICA in the 3 cases in Group II. Postoperative MR imaging showed clear de compression as the high-intensity line and/or spot completely separated fro m the REZ by a low- and/or iso- intensity area in 9 cases of VA compression repositioned to the petrous dura mater, in 11 cases of PICA or AICA compre ssion treated by shredded Teflon pledgers in Group I and in 3 cases in Grou p II. Postoperative MR imagining showed an incomplete separation of any hig h-intensity line and/or spot in the REZ in 2 cases of PICA or AICA compress ion in Group I and in one in Group II. The outcome was excellent in 22 of 2 3 cases with clear decompression. and in 1 of 3 cases of unclear decompress ion. Hemifacial spasm persisted in 3 cases. Oblique sagittal gradient-echo MR imaging is a useful method for postoperative follow-up which can demonst rate changes around the REZ of the facial nerve if hemifacial spasm recurs.