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67th Annual Meeting of the German Society of Neurosurgery (DGNC)
Joint Meeting with the Korean Neurosurgical Society (KNS)

German Society of Neurosurgery (DGNC)

12 - 15 June 2016, Frankfurt am Main

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Robustness of intraoperative monitoring of facial nerve motor evoked potentials

Meeting Abstract

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  • Johannes Sarnthein - Klinik für Neurochirurgie, UniversitätsSpital Zürich, Switzerland; Universität Zürich, Switzerland; Zurich Neuroscience Center, ETHZ, Zurich, Switzerland
  • Niklaus Krayenbühl - Klinik für Neurochirurgie, UniversitätsSpital Zürich, Switzerland; Universität Zürich, Switzerland
  • Oliver Bozinov - Klinik für Neurochirurgie, UniversitätsSpital Zürich, Switzerland; Universität Zürich, Switzerland

Deutsche Gesellschaft für Neurochirurgie. 67. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC), 1. Joint Meeting mit der Koreanischen Gesellschaft für Neurochirurgie (KNS). Frankfurt am Main, 12.-15.06.2016. Düsseldorf: German Medical Science GMS Publishing House; 2016. DocMI.07.08

doi: 10.3205/16dgnc281, urn:nbn:de:0183-16dgnc2814

Published: June 8, 2016

© 2016 Sarnthein et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution 4.0 License. See license information at http://creativecommons.org/licenses/by/4.0/.

Outline

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Objective: To determine whether the facial nerve (FN) transcranial motor-evoked potential (FNMEP) during neurosurgical interventions is a robust modality of intraoperative neurophysiological monitoring.

Method: We included 200 consecutive surgeries 2011 - 2015 (mean patient age 43 ± 21y, 102 female) that were operated on with FNMEP monitoring. We routinely stimulated transcranially with a train of 5 pulses (width 0.5 ms, interval 2 ms) and ruled out peripheral conduction with an single control pulse preceding the train by >20ms. During surgery, we maintained constant response amplitude by increasing the stimulation intensity and aimed to establish a warning criterion based on the “threshold-level” method. A threshold increase of greater than 20 mA for eliciting the FNMEP in the most reliable facial nerve target muscle was considered evidence for possibly reduced postoperative facial nerve function and communicated to the surgeon.

Results: Monitoring of the FNMEP was feasible in 186/200 surgeries (93%) in at least one facial nerve target muscle. The orbicularis oris muscle yielded the best result (80% of the trials). The mean stimulation threshold was 74 mA for the FNMEP and 60 mA for the motor evoked potential (MEP) of the thenar muscles. A threshold increase was communicated in 50/186 surgeries (27%).

Conclusions: FNMEP monitoring can be applied routinely during neurosurgical interventions. Stimulation intensity is in the same range as upper limb MEP. FNMEP is complementary to direct electrical FN stimulation and continuous EMG monitoring of FN target muscles.