Intraoperative detection of a false-negative facial motor evoked potential by direct facial nerve stimulation during vestibular schwannoma surgery: A case report

False-negative transcranial facial motor evoked potential (FMEP) findings have previously been recognized retrospectively through discrepancies between preserved intraoperative FMEPs and postoperative facial palsy. To the best of our knowledge, no previous report has demonstrated a false-negative FMEP finding intraoperatively using direct facial nerve stimulation....

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Surgeons operating on vestibular schwannoma should consider supplementing standard facial motor evoked potential monitoring with direct facial nerve stimulation to detect false-negative signals that could mask impending nerve injury.

False-negative intraoperative neuromonitoring is a known risk in vestibular schwannoma surgery; this case highlights a specific rescue technique that may reduce rates of postoperative facial palsy — a major quality-of-life outcome for patients.

1. 01Standard facial motor evoked potentials (fMEPs) produced a false-negative result during vestibular schwannoma resection.
2. 02Direct facial nerve stimulation successfully detected the monitoring failure in real time.
3. 03Timely detection allowed surgical adjustment, potentially preventing permanent facial nerve damage.
4. 04Case underscores limitations of relying on a single intraoperative neuromonitoring modality.
5. 05Published in Surgical Neurology International.

PMID

42974267

DOI

10.25259/SNI_941_2026.

Journal

Surgical Neurology International

Publication type

case_report

Evidence level

4

Sample size

1

Population

Single patient undergoing vestibular schwannoma surgical resection with intraoperative neuromonitoring

Intervention

Direct facial nerve stimulation as adjunct to standard facial motor evoked potential monitoring

Comparator

Standard facial motor evoked potential (fMEP) monitoring alone