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Updated: Sep 29, 2025
Microvascular Decompression: Salient Surgical Principles and Technical Nuances
Published on: July 5, 2011
Usefulness of intraoperative monitoring in microvascular decompression for hemifacial spasm: a systematic review and
Lyndon Sprenghers1, Robin Lemmens2, Johannes van Loon3
1Faculty of Medicine, University of Leuven, Leuven, Belgium.
Objective:
To review the diagnostic accuracy and possible added value of Brainstem Auditory Evoked Potentials (BAEP) monitoring and Lateral Spread Response (LSR) monitoring in microvascular decompression surgery for hemifacial spasms.
Methods:
For this systematic review we followed the PRISMA guidelines. We searched different databases and bibliographies of articles. We included studies on BAEP and LSR monitoring that reported data on hearing outcome or efficacy. Selected studies were assessed for bias using the MINORS tool.
Results:
64 articles were selected for qualitative synthesis, 42 met inclusion criteria for meta-analysis. The overall incidence of hearing loss was 3.4%. For BAEP monitoring AUC and pooled OR with 95% confidence interval were 0.911 (0.753-0.933) and 7.99 (3.85-16.60) respectively. Short-term data on LSR monitoring showed an overall spasm relief rate of 89% with pooled OR, sensitivity and specificity with a 95% confidence interval of 8.80 (4.82-16.08), 0.911 (0.863-0.943) and 0.451 (0.342-0.564) respectively. Long-term data on LSR monitoring showed an overall spasm relief rate of 95% with pooled OR, sensitivity and specificity with a 95% confidence interval of 4.06 (2.15-7.64), 0.871 (0.817-0.911) and 0.39 (0.294-0.495) respectively.
Conclusion:
The alarm criteria, a wave V latency prolongation of 1ms or a wave V amplitude decrement of 50%, proposed by the 'American Clinical Neurophysiology Society' are a sensitive predictor for postoperative hearing loss. Other BAEP wave changes, for example, complete loss of wave V, are more specific but correspond to irreversible damage and are therefore not useful as warning criteria. LSR monitoring has high diagnostic accuracy at short-term follow-up. At long-term follow-up, diagnostic accuracy decreases because most patients get spasm relief regardless of their LSR status. LSR persistence after surgery has a good long-term outcome, as long as an extensive exploration of the facial nerve has been performed.
Insights
Brainstem Auditory Evoked Potentials (BAEP) monitoring effectively predicts hearing loss after hemifacial spasm surgery. Lateral Spread Response (LSR) monitoring shows high accuracy for short-term spasm relief, with good long-term outcomes when the facial nerve is thoroughly explored.
Area of Science:
- Neurosurgery
- Neurophysiology
- Audiology
Background:
- Microvascular decompression surgery is a primary treatment for hemifacial spasms.
- Intraoperative monitoring is crucial for preserving neurological function during these procedures.
- Brainstem Auditory Evoked Potentials (BAEP) and Lateral Spread Response (LSR) are electrophysiological techniques used for monitoring.
Purpose of the Study:
- To systematically review the diagnostic accuracy and clinical utility of BAEP and LSR monitoring.
- To evaluate their added value in microvascular decompression surgery for hemifacial spasms.
- To assess the prediction of hearing outcomes and surgical efficacy.
Main Methods:
- Systematic review adhering to PRISMA guidelines.
- Searched multiple databases and article bibliographies for relevant studies.
- Included studies reporting hearing outcomes or efficacy data for BAEP and LSR monitoring; assessed bias using the MINORS tool.
Main Results:
- Overall incidence of hearing loss was 3.4%.
- BAEP monitoring showed high diagnostic accuracy (AUC 0.911) for predicting hearing loss.
- LSR monitoring demonstrated high short-term spasm relief rates (89%) and diagnostic accuracy (sensitivity 0.911), with excellent long-term relief (95%).
Conclusions:
- BAEP alarm criteria (1ms wave V latency prolongation or 50% amplitude decrement) are sensitive predictors of postoperative hearing loss.
- LSR monitoring offers high diagnostic accuracy in the short term, though its predictive value diminishes long-term as most patients achieve relief.
- Persistent LSR after surgery correlates with good long-term outcomes, provided extensive facial nerve exploration was performed.
