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60th Annual Meeting of the German Society of Neurosurgery (DGNC)
Joint Meeting with the Benelux countries and Bulgaria

German Society of Neurosurgery (DGNC)

24 - 27 May 2009, Münster

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Neurophysiological mapping and monitoring of the spinal cord during surgery for intramedullary spinal gliomas

Meeting Abstract

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  • O. Suess - Neurochirurgische Klinik, Campus Benjamin Franklin, Charité - Universitätsmedizin Berlin
  • T. Picht - Neurochirurgische Klinik, Campus Benjamin Franklin, Charité - Universitätsmedizin Berlin
  • M. Cabraja - Neurochirurgische Klinik, Campus Virchow-Klinikum, Charité - Universitätsmedizin Berlin
  • P. Vajkoczy - Neurochirurgische Klinik, Campus Virchow-Klinikum, Charité - Universitätsmedizin Berlin
  • T. Kombos - Neurochirurgische Klinik, Campus Benjamin Franklin, Charité - Universitätsmedizin Berlin

Deutsche Gesellschaft für Neurochirurgie. 60. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC), Joint Meeting mit den Benelux-Ländern und Bulgarien. Münster, 24.-27.05.2009. Düsseldorf: German Medical Science GMS Publishing House; 2009. DocP11-08

doi: 10.3205/09dgnc371, urn:nbn:de:0183-09dgnc3718

Published: May 20, 2009

© 2009 Suess et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by-nc-nd/3.0/deed.en). You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.

Outline

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Objective: Intramedullary spinal gliomas (IMSGs) are a rare pathology. They account for 20-25% of all intramedullary spinal cord tumors (ICSTs), which is only 6-8% of all intraspinal neoplasms and less than 0.8% of all CNS tumors. Gross total removal of IMSGs carries a high risk of surgical morbidity. That is why biopsy, dural decompression, and radiotherapy are favored by many surgeons. However, even biopsy remains challenging because of tumor-distorted anatomy, close relation of tumor and spinal tracts, and vulnerable spinal cord vascularization.

Methods: Muscle CMAP analysis was used in 8 cases of cervical and further 4 cases of thoracic spinal gliomas (7x WHO II, 5x WHO III) a) with direct bipolar stimulation of the exposed myelon [monophasic square wave impulse; 3.0 Hz; 0.1ms; 0.1-2.0mA] to map functional anatomy, and b) with a transcranial multipulse technique [cork screw electrodes at C1/2, C2/1, C3/4, C4/3 or Cz/6; train of 5; 500Hz; 0.3ms; max. 100mA] for continuous monitoring of the ascending and descending pathways. Tibialis SEPs were recorded from Cz/Cz+6cm and bilaterally evoked with 4.7Hz, 0.2ms and max. 60mA.

Results: IOM maps of the myelon showed corticospinal tract distortions as well as midline shifts due to tumor invasion of up to 4.8 mm. The sensitivity of evoked CMAP changes for new neurological deficits or an exacerbation of pre-existing symptoms was 97% with a specificity of 31%, positive predictive value was 0.153, and negative predictive value was 0.946. Correlation was highest with sustained mechanical traction, compression, and bipolar coagulation. In addition, SEP sensitivity was only 26% but with a specificity of 92%.

Conclusions: IOM allows to functionally map the spinal cord surface and to monitor spinal tract integrity, helping to define the best point of entry and to monitor impending danger to the myelon before irreversible damage occurs, as documented e.g. by high CMAP sensitivity and low positive predictive value. IOM provides online functional feedback to the surgeon and may predict postoperative neurological function. However, at least well-designed class II-evidence studies have to prove the ultimate benefit of IOM for the long-term outcome in IMSG surgery.