gms | German Medical Science

68th Annual Meeting of the German Society of Neurosurgery (DGNC)
7th Joint Meeting with the British Neurosurgical Society (SBNS)

German Society of Neurosurgery (DGNC)

14 - 17 May 2017, Magdeburg

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Predictive value of transcranial motor-evoked potentials and electromyography for postoperative facial motor function after vestibular schwannoma surgery

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  • Georgios Naros - Department of Neurosurgery, Eberhard Karls University of Tübingen, Tübingen, Deutschland
  • Leonidas Trakolis - Department of Neurosurgery, Eberhard Karls University of Tübingen, Tübingen, Deutschland
  • Marina Liebsch - Department of Neurosurgery, Eberhard Karls University of Tübingen, Tübingen, Deutschland
  • Marcos Tatagiba - Department of Neurosurgery, Eberhard Karls University of Tübingen, Tübingen, Deutschland

Deutsche Gesellschaft für Neurochirurgie. Society of British Neurological Surgeons. 68. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC), 7. Joint Meeting mit der Society of British Neurological Surgeons (SBNS). Magdeburg, 14.-17.05.2017. Düsseldorf: German Medical Science GMS Publishing House; 2017. DocMi.18.07

doi: 10.3205/17dgnc490, urn:nbn:de:0183-17dgnc4907

Published: June 9, 2017

© 2017 Naros 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

Text

Objective: Maintaining facial nerve function is a major concern in vestibular schwannoma surgery. Still, tumor size is one of the most important factors predicting postoperative facial palsy (PFP). On the other side, continuous intraoperative neuromonitoring (INM) of transcranial facial motor-evoked potentials (fMEP) and free-running facial electromyography (fEMG) is applied routinely to prevent PFP. While fMEP amplitude reduction of 50% and the occurrence of spontaneous high-frequency fEMG activity (A-trains, AT) are accepted to indicate facial nerve distress, there is only limited data concerning the predictive value of these measures in the background of different tumor sizes.

Methods: This retrospective study includes 507 consecutive patients (age 49.1±12.9, 52.3% female) without any preoperative facial deficit undergoing surgical removal of a vestibular schwannoma under continuous INM (fMEP and fEMG). We evaluated the sensitivity (SENS) and specificity (SPEC) of fMEP amplitude reduction (>50%) and AT for the occurrence of a significant PFP on the House & Brackman Scale (H&B) ≥ 3. Tumor size was graded preoperatively by the Hannover classification T1-4 (T1/2: 26.9%, T3: 39.8%, T4: 33.3%).

Results: fMEPs were measurable in 480/507 patients (94.7%). AT showed an overall SENS 46.7%, SPEC 58.0% while fMEP had an overall SENS 45.2%, SPEC 88.6%. Combining fMEP and AT increased SENS while reducing SPEC (76,3 % and 52,8 %, respectively). For both fMEP and fEMG there was an increase of SENS in larger tumors while SPEC decreased.

Conclusion: INM of facial nerve function based on fMEPs showed higher sensitivity and specificity that INM based on AT. However, while fMEPs show a good specificity, we found a rather low sensitivity. The combination fMEP and fEMG revealed the best predictive value for the occurrence of postoperative facial palsy after vestibular schwannoma surgery.