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Updated: Aug 7, 2026
Microvascular Decompression: Salient Surgical Principles and Technical Nuances
Published on: July 5, 2011
[Abnormal muscle response monitoring during microvascular decompression for hemifacial spasm and long term results]
Masafumi Fukuda1, Shinya Yamashita, Tadashi Kawaguchi
1Department of Neurosurgery, Brain Research Institute, University of Niigata, 1-757 Asahimachi-dori, Niigata-City 951-8585, Japan. mfuku529@bri.niigata-u.ac.jp
Objective:
There is some debate over the reliability of intraoperative abnormal muscle response (AMR) monitoring as an indicator of postoperative long-term outcome in patients with hemifacial spasm (HFS). We investigated whether AMR findings obtained during microvascular decompression reflect postoperative long-term outcome. MATERIAS AND METHODS: Subjects were 51 HFS patients who underwent AMR monitoring during surgery. AMR recordings were obtained from the mentalis muscle by electrical stimulation of the temporal branch of the facial nerve and from the orbicularis oculi muscles by stimulation of the marginal mandibular branch. Postoperative follow-up was more than 5 years (range 61-118 months, mean 87 months).
Results:
In 37 patients, AMR disappeared after vascular decompression. Among those patients, only one presented with spasm at the final follow-up examination. In 6 of 7 patients with AMR that disappeared early before the completion of decompression, hemifacial spasm resolved completely. Five of six patients in whom AMR still remained but with decreased amplitude at the end of surgery experienced complete resolution.
Conclusions:
Our findings suggest that intraoperative cessation including prior to decompression or decreased amplitude of AMR at the end of surgery indicates a high likelihood of postoperative long-term relief of HFS. We believe that intraoperative AMR monitoring is useful in MVD surgery for HFS.
Insights
Intraoperative abnormal muscle response (AMR) monitoring during microvascular decompression for hemifacial spasm (HFS) can predict long-term outcomes. Cessation or decreased AMR amplitude suggests a high likelihood of sustained HFS relief.
Area of Science:
- Neurosurgery
- Neurology
- Clinical Electrophysiology
Context:
- Hemifacial spasm (HFS) is a neuromuscular disorder characterized by involuntary contractions of facial muscles.
- Microvascular decompression (MVD) is a primary surgical treatment for HFS, aiming to alleviate neurovascular compression.
- The reliability of intraoperative monitoring, specifically abnormal muscle response (AMR), in predicting long-term surgical success for HFS remains debated.
Purpose:
- To investigate the correlation between intraoperative abnormal muscle response (AMR) findings during microvascular decompression (MVD) and the long-term postoperative outcomes in patients with hemifacial spasm (HFS).
- To assess the predictive value of AMR cessation or amplitude changes for sustained relief of HFS symptoms following MVD surgery.
Summary:
- This study analyzed 51 patients undergoing MVD for HFS, monitoring AMR from the mentalis and orbicularis oculi muscles.
- A significant majority of patients (37) showed AMR disappearance post-decompression, with only one experiencing recurrent spasms at long-term follow-up (mean 87 months).
- Early AMR cessation or decreased amplitude at the end of surgery correlated strongly with complete or significant resolution of hemifacial spasm.
Impact:
- Intraoperative AMR monitoring appears to be a valuable tool for predicting the long-term efficacy of MVD in HFS patients.
- These findings support the routine use of AMR monitoring during MVD surgery to provide prognostic information.
- Confirmation of successful decompression via AMR can guide surgical decisions and patient expectations regarding HFS recurrence.
