Although microvascular decompression (MVD) is a reliable treatment for hemifacial spasm (HFS), delayed postoperative relief is one of its main issues. We previously evaluated the morphology of the lateral spread response (LSR) and reported the correlation between delayed relief after MVD and polyphasic morphology of the LSR. The purpose of this study was to investigate the correlation between the morphology of the LSR with stimulation of the temporal and mandibular branches of the facial nerve and delayed relief of persistent HFS after MVD. We retrospectively analysed and compared data from 49 of 205 consecutive patients who underwent MVD for HFS at our hospital between January 2015 and March 2022. Based on the pattern of the initial LSR morphology, patients were divided into 4 groups (LSR with temporal branch stimulation/LSR with mandibular branch stimulation
polyphasic/polyphasic group, polyphasic/monophasic group, monophasic/polyphasic group, monophasic/monophasic group). The results of MVD surgery for HFS were evaluated 1 week, 1 month and 1 year postoperatively, by evaluating whether or not the symptoms of HFS persisted at the time of each follow-up. We found significant differences in residual postoperative HFS 1 week postoperatively among the 4 groups (p <
0.05), as assessed using m*n Yates chi-square test. There is a significant correlation between delayed relief after MVD and polyphasic morphology of the initial LSR in patients with HFS. The LSR with temporal rather than mandibular branch stimulation might be useful for predicting delayed relief following MVD in HFS patients.