gms | German Medical Science

59th Annual Meeting of the German Society of Neurosurgery (DGNC)
3rd Joint Meeting with the Italian Neurosurgical Society (SINch)

German Society of Neurosurgery (DGNC)

1 - 4 June 2008, Würzburg

Intraoperative monitoring of motor cranial nerves during surgery of tumors involving the lower brain stem and the floor of the fourth ventricle in children

Intraoperatives Monitoring der motorischen Hirnnerven während der mikrochirurgischen Resektion von Tumoren im Bereich des unteren Hirnstamms und vierten Ventrikels bei Kindern

Meeting Abstract

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  • corresponding author R. Sircar - Abt. Allgemeine Neurochirurgie, Universitätsklinikum Freiburg, Freiburg
  • M. J. Shah - Abt. Allgemeine Neurochirurgie, Universitätsklinikum Freiburg, Freiburg
  • V. Van Velthoven - Abt. Allgemeine Neurochirurgie, Universitätsklinikum Freiburg, Freiburg

Deutsche Gesellschaft für Neurochirurgie. Società Italiana di Neurochirurgia. 59. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie e.V. (DGNC), 3. Joint Meeting mit der Italienischen Gesellschaft für Neurochirurgie (SINch). Würzburg, 01.-04.06.2008. Düsseldorf: German Medical Science GMS Publishing House; 2008. DocMI.02.05

The electronic version of this article is the complete one and can be found online at:

Published: May 30, 2008

© 2008 Sircar et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.



Objective: The extent of tumor reduction through surgery is the main determining factor in the prognosis of invasive tumors of the posterior fossa in children and adults. In this study we assessed whether intraoperative monitoring and mapping of the motor cranial nerves and nuclei during surgery of tumors involving the fourth ventricle and lower brain stem helps to achieve radical tumor resection while preserving function in the pediatric patient population.

Methods: Electromyographic activity (EMG) was continually recorded from the target muscles of motor cranial nerves (CN) in 19 patients (11 male, 8 female; median age 7 years, range 5 months – 16 years), who were operated on tumors involving the lower brainstem and fourth ventricle between 2004 and 2007. EMG-recordings were obtained in all cases from the target muscles of CN VII, CN IX, CN X and CN XII with needle electrodes using a bipolar technique. In addition CN III, CN IV, CN V, CN VI and CN XI were recorded in some cases. Free-running EMG was recorded throughout and stored. Online analysis during surgery included detection of pathological muscle activity and localization of cranial nerves or their respective nuclei through electrical stimulation using a concentric bipolar stimulation probe. Additional monitoring consisted of SEP (9 patients), MEP (4 patients) and AEP (11 patients).

Results: Pathological muscle activity could be detected in 12 of 19 patients (63%). This resulted in a change of the operative strategy in 10 patients (52%). Mapping of cranial motor nuclei and nerves was performed successfully in 5 patients (26%). Five patients (36%) showed a new postoperative neurological deficit which recovered completely until discharge in 3 cases. 2 patients (10%) showed a persisting neurological deficit in the monitored muscle groups. Manipulation on the floor of the fourth ventricle could be readily detected in 9 patients (47%). Radical tumor resection could be achieved in 13 of 19 patients (68%).

Conclusions: Intraoperative monitoring of the EMG-activity of the cranial motor nerves resulted in a change of the surgical strategy in 10 of 19 patients (52%). This method proved to be a helpful tool in achieving radical resection of tumors involving the brainstem and the fourth ventricle while maintaining good life quality of the treated children.