Three-Dimensional Short-Range MR Angiography and Multiplanar Reconstruction Images in the Evaluation of Neurovascular Compression in Hemifacial Spasm

ABSTRACT

PURPOSE: To evaluate the diagnostic efficacy of three-dimensional(3D) short-range MR angiography(MRA) andmultiplanar reconstruction(MPR) imaging in hemifacial spasm(HS). MATERIALS AND METHODS: Two hundreds patientswith HS were studied using a 1.5T MRI system with a 3D time-of-flight(TOF) MRA sequence. To reconstructshort-range MRA, 6-10 source images near the 7-8th cranial nerve complex were processed using a maximum-intensityprojection technique. In addition, an MPR technique was used to investigate neurovascular compression. We observedthe relationship between the root-exit zone(REZ) of the 7th cranial nerve and compressive vessel, and identifiedthe compressive vessels on symptomatic sides. To investigate neurovascular contact, asymptomatic contralateralsides were also evaluated. RESULTS: MRI showed that in 197 of 200 patients there was vascular compression orcontact with the facial nerve REZ on symptomatic sides. One of the three remaining patients was suffering fromacoustic neurinoma on the symptomatic side, while in two patients there were no definite abnormal findings. Compressive vessels were demonstrated in all 197 patients; 80 cases involved the anterior inferior cerebellarartery(AICA), 74 the posterior cerebellar artery(PICA), 13 the vertebral artery(VA), 16 the VA and AICA, eight theVA and PICA, and six the AICA and PICA. In all 197 patients, compressive vessels were reconstructed on one 3Dshort-range MRA image without discontinuation from vertebral or basilar arteries. 3D MPR studies providedadditional information such as the direction of compression and course of the compressive vessel. In 31 patientsthere was neurovascular contact on the contralateral side at the 7-8th cranial nerve complex. CONCLUSION: Inpatients with HS, 3D short-range MRA and MPR images are excellent and very helpful for the investigation ofneurovascular compression and the identification of compressive vessels.