Factors associated with persistent abnormal muscle responses in microvascular decompression for hemifacial spasm and prognostic analysis.

Objective: An abnormal muscle response (AMR) is an important electrophysiological indicator for the diagnosis, treatment, and prognosis of hemifacial spasm (HFS). The purpose of this study was to analyze the factors associated with and to establish a predictive model for the persistence of AMRs during microvascular decompression (MVD), while also evaluating the relationship between the disappearance of AMRs and delayed recovery.

Methods: In this retrospective study, authors collected clinical data from patients with HFS who underwent MVD at The First Affiliated Hospital of Dalian Medical University between August 2019 and August 2024. Factors associated with the persistence of AMRs were analyzed, and a predictive model for their persistence was developed.

Results: The results showed the disappearance of AMRs at a rate of 78.3% among the 157 patients included in the study. Factors influencing the persistence of AMRs included disease duration, preoperative symptom severity, carbamazepine use, number of responsible vessels, preoperative AMR amplitude, cerebellar retraction depth, and degree of responsible vessel displacement. The predictive model achieved an area under the curve of 0.931, indicating high accuracy. Follow-up data revealed that the persistence of AMRs was associated with recovery rates at 3 months postoperatively (p < 0.01).

Conclusions: Risk factors for the persistence of AMRs can be used to predict the probability of persistent intraoperative AMRs. An intraoperative AMR that persists despite having a low preoperative predicted probability may indicate inadequate facial nerve decompression or undetected offending vessels, requiring either additional surgical exploration or transposition of the offending vessels. Conversely, when an AMR persists in the context of a high preoperative predicted probability, the MVD procedure can be safely terminated after confirming adequate decompression to minimize surgical complications. Patients with persistent AMRs may experience delayed recovery, with symptom relief potentially taking 3 months. If symptoms persist without improvement for 6 months to a year, a second surgery can be considered.