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65th Annual Meeting of the German Society of Neurosurgery (DGNC)

German Society of Neurosurgery (DGNC)

11 - 14 May 2014, Dresden

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Intraoperative subcortical stimulation: How far are you from the corticospinal tract?

Meeting Abstract

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  • Ehab Shiban - Neurochirurgische Klinik und Poliklinik, Klinikum rechts der Isar, Technische Universität München
  • Sandro Krieg - Neurochirurgische Klinik und Poliklinik, Klinikum rechts der Isar, Technische Universität München
  • Thomas Obermueller - Neurochirurgische Klinik und Poliklinik, Klinikum rechts der Isar, Technische Universität München
  • Maria Wostrack - Neurochirurgische Klinik und Poliklinik, Klinikum rechts der Isar, Technische Universität München
  • Bernhard Meyer - Neurochirurgische Klinik und Poliklinik, Klinikum rechts der Isar, Technische Universität München
  • Florian Ringel - Neurochirurgische Klinik und Poliklinik, Klinikum rechts der Isar, Technische Universität München

Deutsche Gesellschaft für Neurochirurgie. 65. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC). Dresden, 11.-14.05.2014. Düsseldorf: German Medical Science GMS Publishing House; 2014. DocMI.14.04

doi: 10.3205/14dgnc348, urn:nbn:de:0183-14dgnc3488

Published: May 13, 2014

© 2014 Shiban 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: Subcortical stimulation is a method to evaluate the distance from the stimulation site to the motor tract (CST) and to decide whether the resection should be terminated. A clear correlation between stimulation intensity and the distance to the CST has not been properly substantiated. To date various reports with different stimulation conditions have reached different results. The aim of this study was to investigate various stimulation conditions in order to better define the correlation between the subcortical stimulation and the distance to the CST.

Method: Monopolar subcortical stimulation (mSCS) was performed in addition to continuous MEP monitoring in 37 consecutive patients with a motor eloquent lesion. The functional boundaries of the resection were identified with the help of subcortical stimulation. At the end of resection, the point at which a MEP response was still measurable with minimal subcortical stimulation intensity was marked with a titanium clip was. At this point different stimulation variants were examined with cathodal or anodal stimulation at 0.3, 0.5 and 0.7 ms pulse duration, respectively. The distance between the CST (based on the postoperative DTI data) and the titanium clip was measured. The correlation between the distance and the mSCS the electric charge (µCoulumb) was calculated.

Results: mSCS was successful in all patients. One patient developed a postoperative bleed and displacement of the titanium clip and was therefore excluded from the study. There were no new postoperative deficits. Transient new postoperative neurological deficit was observed in 14% (5/36) of cases. Gross total resection was achieved in 75% (27/36) and subtotal resection (>80% of tumor mass) in 25% (9/36) of cases. Current intensity ( mA x ms) was blotted against the measured distance between the CST and the titanium clip. Regression analysis reviled a nonlinear correlation. For anodal stimulation: Current = Distance**0,709 (R2= 0,865). For cathodal stimulation: Current = Distance**0,606 (R2 = 0,889)

Conclusions: The subcortical stimulation is an excellent intraoperative method to determine the distance to the CST during resection of motor eloquent lesions. This should minimize the risk of injuring the CST. There is a nonlinear correlation between stimulation current and the distance to the CST.