PREDICTION OF VERTEBRAL ARTERY COMPRESSION IN PATIENTS WITH HEMIFACIAL SPASM USING OBLIQUE SAGITTAL MR-IMAGING

To discriminate between the Various compressing vessels of the facial nerves in patients with hemifacial spasm, pre-operative oblique sagitt al gradient-echo MR imaging was performed. Forty-two patients underwen t pre-operative MR imaging and microvascular decompression. The MR ima ges were divided according to findings into three groups as follows: G roup A, a thick and/or long high-intensity line along the root exit zo ne (REZ) of the facial nerve; Group B, a thin and/or short high-intens ity line along the REZ; and Group C, an unreliable image around the RE Z. Fifteen images were classified as Group A, 19 as Group B, and 8 as Group C.;In Group A, vertebral artery (VA) compression was confirmed i ntra-operatively in 12 cases and posterior inferior cerebellar artery (PICA) or anterior inferior cerebellar artery (AICA) compression in 3. In Group B, PICA or AICA compression was confirmed intra-operatively in all cases. In Group C, PICA or AICA compression was confirmed intra operatively in 7 cases and no compression in one. In all cases of VA c ompression of the facial nerve, the oblique sagittal gradient-echo ima ges demonstrated a thick and/or long high intensity line along the REZ . Oblique sagittal gradient-echo MR imaging is a useful preoperative p lanning aid, which can predict the possibility of VA compression prior to microvascular decompression for hemifacial spasm.