Warning Values of Intraoperative BAEP Monitoring During Microvascular  Decompression for Hemifacial Spasm: A Tool for Safety and Functional Preservation: WSSFN 2025 Interim Meeting. Abstract 0063

Gustavo Polo; Andrei Brinzeu; Vincent Marneffe; Catherine Fischer; Marc Sindou

doi:10.47924/neurotarget2025521

Autores/as

Gustavo Polo Hôpital Neurologique Lyon. France.
Andrei Brinzeu Hôpital Neurologique Lyon. France.
Vincent Marneffe Clinique Saint-Pierre Ottignies. France.
Catherine Fischer Hôpital Neurologique Lyon. France.
Marc Sindou Hôpital Neurologique Lyon. France.

DOI:

https://doi.org/10.47924/neurotarget2025521

Resumen

Introduction: Microvascular decompression (MVD) is the gold standard treatment for hemifacial spasm (HFS), but it carries a risk of auditory morbidity, primarily due to lateral traction on the eighth cranial nerve during exposure of the facial nerve. This study aimed to: (1) assess the incidence and mechanisms of hearing loss during MVD for HFS; (2) identify critical intraoperative changes in brainstem auditory evoked potentials (BAEPs) that predict postoperative outcomes; and (3) define practical intraoperative warning thresholds.
Method: We retrospectively analyzed 100 patients undergoing MVD for HFS, including 84 with detailed intraoperative BAEP recordings and 34 earlier cases. BAEPs were continuously monitored, focusing on Wave I–V interpeak latency, Wave V latency shifts, and amplitude changes. Pre- and postoperative auditory function was evaluated using pure tone average (PTA). Correlations between intraoperative changes and hearing outcomes were analyzed to identify risk thresholds.
Result: Hearing was preserved in 88% of monitored patients. Hearing loss occurred in 9.5%, and complete deafness in 2.3%. Wave V latency delay was the most sensitive intraoperative marker. Mean delay was 0.61 ms (±0.36) in patients without hearing loss, and 1.05 ms (±0.64) in those with hearing decline. Wave V abolition was associated with permanent deafness. Most BAEP changes occurred during cerebellar retraction. Earlier cases without systematic monitoring showed a higher deafness rate (3/7) than later ones (2/93).
Discussion: BAEP monitoring reduces the risk of hearing loss by detecting reversible changes during MVD. We propose three intraoperative warning thresholds: • 0.4 ms Wave V delay – “watching” • 0.6 ms – “warning” • 1.0 ms or BAEP loss – “critical” These thresholds help prevent irreversible auditory damage in functional neurosurgery.

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Citas

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Marneffe V, Polo G, Fischer C, Sindou M. Décompression Vasculaire Microchirurgicale Pour Spasme Hémifacial. Résultats cliniques à plus d’un an et facteurs pronostiques. Etude d’une série de 100 cas. Neurochirurgie. 2003;49(5):527-535.

Polo G, Fischer C, Sindou M, Marneffe V. Brainstem Auditory Evoked Potential (BAEP) Monitoring During Microvascular Decompression For Hemifacial Spasm: Intraoperative BAEP Changes And Warning Values To Prevent Hearing Loss- Prospective Study In A Consecutive Series Of 84 Patients. Neurosurgery. 2004; 54(1)

Polo G, Fischer C. Intraoperative monitoring of brainstem auditory evoked potentials during microvascular decompression of cranial nerves in cerebellopontine angle. Neurochirurgie. 2009;55(2):152-7.