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66th Annual Meeting of the German Society of Neurosurgery (DGNC)
Friendship Meeting with the Italian Society of Neurosurgery (SINch)

German Society of Neurosurgery (DGNC)

7 - 10 June 2015, Karlsruhe

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Corticospinal tract reconstruction based on navigated transcranial stimulation in brainstem tumors: Description of technique and clinical potential

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  • Anna Zdunczyk - Klinik für Neurochirurgie, Charité - Universitätsmedizin Berlin
  • Brendon Bagley - Klinik für Neurochirurgie, Charité - Universitätsmedizin Berlin
  • Thomas Picht - Klinik für Neurochirurgie, Charité - Universitätsmedizin Berlin
  • Peter Vajkoczy - Klinik für Neurochirurgie, Charité - Universitätsmedizin Berlin

Deutsche Gesellschaft für Neurochirurgie. 66. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie (DGNC). Karlsruhe, 07.-10.06.2015. Düsseldorf: German Medical Science GMS Publishing House; 2015. DocMI.17.02

doi: 10.3205/15dgnc379, urn:nbn:de:0183-15dgnc3791

Published: June 2, 2015

© 2015 Zdunczyk 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

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Objective: Surgical resection of brainstem tumors is still associated with a high risk of postoperative motor deficit due to complex anatomy and possible impingement of the corticospinal tracts by the tumor. The current study aims at establishing a reliable and objective way to visualize descending motor pathways with navigated TMS-based fiber tracking.

Method: For this pilot study 10 patients with brainstem tumors were examined with nTMS prior to surgery. We depicted the resting motor threshold (RMT) and recruitment curve (RC) for the FDI muscle. Using the MEP responses at 105% RMT and 160% RMT the representation area of hand and leg function was determined. Coordinates for MEP responses were imported into the fiber tracking software and set as seed points for tractography. Then the individual FA threshold, which is the highest FA value leading to visualization of tracts at a predefined minimum fiber length of 110 mm, was determined. Lastly, fiber tracking was performed at a fractional anisotropy value of 75% of the individual FA threshold.

Results: Mapping of the motor cortex and corticospinal tract reconstruction was successful in all patients. Tractography results facilitated decision for surgical approach and intraoperative orientation resulting in a favorable postoperative outcome (modified ranking scale: 0 (30%), 1 (20%), 2 (30%), 4 (20%)). A comparison of nTMS results for RMT and RC in accordance to clinical status allowed for an individual evaluation of possible affected corticospinal tracts.

Conclusions: nTMS based fiber tracking represents an objective visualization method based on functional data. These results provide a valuable instrument for preoperative planning as well as intraoperative orientation and risk stratification.