Evaluation of pre-operative neuroimaging characteristics in patients with primary hemifacial spasm as a prognostic factor of microvascular decompression

•Smaller facial-nerve angle and cross-sectional area of CPA cistern may regard as possible pathogenic factors of primary HFS.•Facial-nerve angle and cross-sectional area of CPA cistern might be used to predict the long-term outcome of MVD.•Examination of entire length of facial nerve and total separation of arachnoid membranes during MVD surgery are essential. The aim of this study was to explore the possible pathogenesis of primary hemifacial spasm (HFS) according to the performances of preoperative high-resolution magnetic resonance (MR) sequence and investigate the correlations between the neuroimaging parameters and the prognosis of microvascular decompression (MVD). 106 patients with HFS and 121 age-matched and gender-matched healthy controls (HCs) were included in this study. Electronic medical records and neuroimaging data were collected. The facial-nerve angle, cross-sectional area of CPA cistern and length of the cistern segment of the facial nerve were measured on affected side and unaffected as well as healthy individuals. The receiver operating characteristic curve was used for assessing the predictive performances. 100 patients achieved complete relief postoperatively. 13 of the 100 complete relief patients developed a relapse in the follow-up. The preoperative facial-pontine angle and cross-sectional area of the CPA cistern on the affected side was significantly smaller than the unaffected side and HC. The facial-pontine angle and the cross-sectional area of the CPA cistern was significantly smaller in recurrent group than the non-recurrent group. The AUC value of both facial-pontine angle and cross-sectional area of the CPA cistern were over 0.7. Small facial-nerve angle and cross-sectional area of CPA cistern may be regarded as the possible pathogenesis of primary HFS. The measurement of facial-nerve angle and cross-sectional area of CPA cistern preoperatively might be used to predict the surgical effect of MVD.