Clinical analysis of abnormal muscle response monitoring for hemifacial spasm during microvascular decompression: a retrospective study.

Background: Microvascular decompression (MVD) is a widely recognized therapeutic approach for the treatment of hemifacial spasm (HFS). Abnormal muscle response (AMR) is a distinctive electromyographic finding exclusively in patients with HFS. The purpose of our investigation was to determine the correlation between changes in intraoperative AMR and surgical efficacy, as well as the incidence of postoperative complications in patients with HFS after undergoing MVD.

Methods: In this retrospective study, we evaluated 145 patients with HFSs treated with MVD, which was maintained for 1 year postoperatively. The subjects were divided into two groups based on the persistence or disappearance of AMR. Continuous monitoring of AMR during surgery provided data on persistence. All patients were followed up 1 day, 30 days, and 1 year after MVD. A range of potential predictive factors, such as patient demographics, symptom duration, and morphology and latency of AMR, were analyzed using binary logistic regression to assess their relationship with postoperative non-cure and delayed cure rates.

Results: The 1 day postoperative cure rate was 77.9%, with a 1 year postoperative cure rate of 94.59% and 1 day postoperative relief rate of 87.6%. A marked distinction was noted between preoperative and 1 year postoperative Cohen grades (P < 0.05). Moreover, 1 day after surgery, the outcome demonstrated significant variability, as shown by the binary logistic regression model (χ² = 62.913, P < 0.05). The results suggested that factors such as age, symptom duration, disappearance of AMR, and preoperative carbamazepine treatment markedly influence outcomes 1 day after surgery. The binary logistic regression model for delayed cure at 1 year showed significant variability (χ² = 54.883, P < 0.05). Furthermore, analysis using generalized estimating equations revealed that the duration of postoperative follow-up significantly impacted Cohen grades, as did the disappearance of AMR, with the grade of AMR disappearance being only 10% of that of non-AMR disappearance (P < 0.05).

Conclusion: Our findings suggest that MVD is an effective intervention for HFS. Our findings also indicate that factors such as patient age, duration of symptoms, disappearance of AMR, and preoperative carbamazepine therapy are significant predictors of 1 day postoperative cure rate. Major predictors for delayed cure at 1 year include age, symptom duration, AMR disappearance, preoperative carbamazepine and botulinum neurotoxin administration, single morphology AMR, and offending vertebral artery.