Predictive Value of Intraoperative Facial Nerve Response Thresholds on the Recovery Effect After Facial Nerve Decompression

Objective To investigate the relationship between the thresholds of intraoperative facial nerve response and postoperative facial nerve function recovery in patients with Bell’s palsy. Methods Clinical data from Bell’s palsy patients who underwent facial nerve decompression surgery at Beijing Tiantan Hospital from October 2015 to October 2022 were collected. Patients who had intraoperative facial nerve monitoring with accurate recording of the facial nerve direct stimulation threshold and had at least 1 year of detailed follow-up were selected for analysis. Patients with postoperative facial nerve function recovery to grade I-II (HB grading) were defined as having good recovery, while those who recovered to grade III or higher were defined as having poor recovery. Patients were divided into two groups (A and B) according to facial nerve reaction excitability, with group A having a direct stimulation threshold of ≤1.5 mA and group B having a direct stimulation threshold of >1.5 mA or an increase in stimulation volume to 3mA, but no neural response waveform was recorded. The relationship between postoperative facial nerve function recovery and facial nerve direct stimulation threshold was compared. Results A total of 36 Bell’s palsy patients were included in this study and underwent facial nerve decompression surgery through the transmastoid-epitympanum approach within 1-3 months after onset. Of the 36 patients, 24 (66.7%) had good recovery and 12 (33.3%) had poor recovery. Only 20 (55.6%, 20/36) patients had facial nerve direct stimulation threshold recorded during the operation, and all were ≤1.5mA (0.1-1.5 mA). The reaction waveforms of 16 (44.4%, 16/36) patients could not be recorded even when facial nerve stimulation increased to 3mA. There was no significant difference in age, gender, lateral discourse, timing of surgery , and preoperative electroneurography (ENoG) in group A and group B, but the good recovery rate of patients in Group A was significantly higher than that in Group B, and the difference was statistically significant (P=0.009). Conclusion For patients with Bell’s palsy undergoing decompression surgery of the facial nerve, the intraoperative direct stimulation threshold of the facial nerve may have some predictive value for postoperative facial nerve function recovery.