gms | German Medical Science

61st Annual Meeting of the German Society of Neurosurgery (DGNC) as part of the Neurowoche 2010
Joint Meeting with the Brazilian Society of Neurosurgery on the 20 September 2010

German Society of Neurosurgery (DGNC)

21 - 25 September 2010, Mannheim

The value of facial motor evoked potentials in the microsurgical treatment of hemifacial spasm

Meeting Abstract

  • Florian Roser - Klinik für Neurochirurgie, Universitätsklinikum Tübingen, Germany
  • Marina Liebsch - Klinik für Neurochirurgie, Universitätsklinikum Tübingen, Germany
  • Artemisia Dimostheni - Klinik für Neurochirurgie, Universitätsklinikum Tübingen, Germany
  • FLorian H. Ebner - Klinik für Neurochirurgie, Universitätsklinikum Tübingen, Germany
  • Marcos S. Tatagiba - Klinik für Neurochirurgie, Universitätsklinikum Tübingen, Germany
  • Marcus Acioly de Sousa - Klinik für Neurochirurgie, Universitätsklinikum Tübingen, Germany

Deutsche Gesellschaft für Neurochirurgie. 61. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC) im Rahmen der Neurowoche 2010. Mannheim, 21.-25.09.2010. Düsseldorf: German Medical Science GMS Publishing House; 2010. DocV1668

DOI: 10.3205/10dgnc141, URN: urn:nbn:de:0183-10dgnc1414

Published: September 16, 2010

© 2010 Roser et al.
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Outline

Text

Objective: Hemifacial spasm (HFS) is thought to be due to facial motor nucleus hyperactivity related to chronic neurovascular contact. Microvascular decompression (MVD) is the only definite treatment rendering high rates of cure. Intraoperative monitoring has been advocated during such procedures by using lateral spread response (LSR) recordings in order to ensure adequate decompression. LSR is presumed to reflect changes in facial motor neuron excitability. As facial motor evoked potentials (FMEP) use the same efferent pathway as LSR, the authors speculated that FMEP should also reflect differences consistent with changes at the facial motor nucleus level and sought to evaluate these potentials following adequate MVD.

Methods: LSR and FMEP were recorded intraoperatively from ten consecutive patients undergoing MVD for HFS. LSR was performed using 5–10 pulses/sec stimulating a peripheral branch with the cathode placed proximally (20–30% above threshold of 1–3mA). Detection was recorded via the adjacent peripheral branch. FMEP was recorded via transcranial electrocortical stimulation using corkscrew electrodes positioned at hemispheric montage (C3/4 and Cz). The contralateral abductor pollicis brevis muscle was used as control response. LSR and FMEP recordings were evaluated at baseline, after MVD and at the end of the surgery.

Results: LSR resolved after MVD in all cases corresponding to successful clinical postoperative outcome. FMEP showed marked changes following MVD ranging from amplitude decrease at increased stimulating voltage to complete potential loss without clinical relevance.

Conclusions: FMEP represents an interesting and additional tool for studying the neurophysiological mechanisms and outcome prediction of HFS. Data in this study support the hypothesis that the development of HFS and its alleviation with MVD may be related to changes in facial motor nucleus activity.