The Guiding Value Of Mri In Facial Nerve Root Exit Zone (rez) For Microvascular Decompression

Objectives:By use of MRI on facial nerve root exit zone (REZ) to determine the corresponding vessels in patients with hemifacial spasm (HFS), and to provide a reliable operative method for microvascular decompression (MVD).Methods:45 patients with HFS (served as patient groups) and 30 healthy volunteers (as normal control groups) were examined with brain T2WI/3D/TSE and 3D-TOF-MRA to understand the neurovascular relationship at the facial nerve REZ. MRI results in diseased or contralateral side and normal control groups were analyzed and random control analysis were given on 45 cases with HFS in which received MVD.Results:(1) In 45 cases of patient groups, the images of neurovascular contact/ compression (NVC) on facial nerve REZ were 43 in the diseased side and 7 in the contralateral side. The images of NVC on facial nerve REZ were 14 in normal control groups. The positive rate of NVC in diseased side of patient groups were significantly higher than that in contralateral side and normal control groups, and the differences both had statistical significance (P<0.05), the positive rate of that in contralateral side and normal control groups had not statistical significance (P>0.05).(2)surgical findings: 45 cases in patient groups received MVD, and surgical results showed NCV on facial nerve REZ in 44 cases.(3) MRI showed that 43 sides of the facial nerve REZ had NVC in symptomatic sides. The corresponding vessels include 3 cases of vertebral artery, 19 cases of the anterior-inferior cerebellar artery, 14 cases of posterior-inferior cerebellar artery, 4 cases of anterior-inferior cerebellar artery and 3 cases of posterior-inferior cerebellar artery. The corresponding vessels form include 31 cases with vascular loop, 12 cases with rows. Operation had confirmed that 44 sides of the facial nerve REZ had NVC. The corresponding vessels include 2 cases of vertebral artery, 19 cases of the anterior-inferior cerebellar artery, 14 cases of posterior-inferior cerebellar artery, 6 cases of anterior-inferior cerebellar artery and 3 cases of posterior-inferior cerebellar artery. The corresponding vessels form include 31 cases with vascular loop, 13 cases with rows.(4) By comparing the results of MRI with operative findings, the true positive rate was 97.73% in 43 cases, false positive rate was 0 in 0 cases and false negative was 2.27 in 1 case. MR neurovascular imaging assessment was valuable for diagnosing HFS with sensitivity 97.73%, specificity 100%, accuracy (97.78%), positive predictive value (100%), negative predictive value (50%) and Youden index 0.98.(5) In 45 HFS patients on the treatment of MVD, symptoms disappeared immediately post-operation in 32 cases (account for 71.11%), and disappeared on 15~60th days after operation in 12 cases (26.67%). There was only one case with symptom relief (2.22%). In addition, there were hearing impairment in 3 cases and facial paralysis in 2 cases, but alleviated on 15~60th days post-operation. No death and disability occurred.Conclusions:NVC on facial nerve REZ were closely related to HFS. Anterior-inferior cerebellar artery was one of the most common corresponding vessels. The diagnostic accuracy and surgical effect of corresponding vessels were improved by MRI in which the sources and anatomical structures of corresponding vessels were clear.