Article
Continuous dynamic mapping of the corticospinal tract during surgery of motor eloquent brain tumors: Evaluation of a new method
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Authors
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Kathleen Seidel
- Klinik für Neurochirurgie, Inselspital, Universitätsklinikum Bern, Schweiz
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Jürgen Beck
- Klinik für Neurochirurgie, Inselspital, Universitätsklinikum Bern, Schweiz
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Philippe Schucht
- Klinik für Neurochirurgie, Inselspital, Universitätsklinikum Bern, Schweiz
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Andreas Raabe
- Klinik für Neurochirurgie, Inselspital, Universitätsklinikum Bern, Schweiz
| Published: | May 13, 2014 |
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Outline
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Objective: We developed a new mapping technique to overcome the temporal and spatial limitations of classical subcortical mapping of the corticospinal tract (CST). The feasibility and safety of continuous (0.4-2 Hz) and dynamic (at the site of and synchronized with tissue resection) subcortical motor mapping was evaluated.
Method: We prospectively studied 128 patients who underwent tumor surgery adjacent to the CST (<1 cm using diffusion tension imaging (DTI) and fiber tracking) with simultaneous subcortical monopolar motor mapping (short train, inter-stimulus interval (ISI) 4.0 ms, pulse duration 500 µs) and a new acoustic motor evoked potential (MEP)-alarm. Continuous (temporal coverage) and dynamic (spatial coverage) mapping was technically realized by integrating the mapping probe at the tip of a new suction device with the concept that this device will be in contact with the tissue where the resection is performed. Motor function was assessed one day after surgery, at discharge, and at 3 months.
Results: All procedures were technically successful. There was a 1:1 correlation of motor thresholds (MTs) for stimulation sites simultaneously mapped with the new suction mapping device and the classic fingerstick probe (24 patients, 74 stimulation points, r=0.996, p<0.001). Lowest individual MTs were as follows (MT, number of patients): >20 mA, n=13; 11-20 mA, n=27; 6-10 mA, n=18; 4-5 mA, n=27; 1-3 mA, n=43. At 3 months, 4 patients (3%) had a persisting postoperative motor deficit, three of which were caused by a vascular injury. One patient had a permanent motor deficit caused by a mechanical injury of the CST.
Conclusions: Continuous dynamic mapping was found to be a feasible and ergonomic technique for localizing the exact site of the CST and distance to the motor fibers. The acoustic feedback and the ability to continuously stimulate the tissue exactly at the site of tissue removal improves the accuracy of mapping, especially at low (<5 mA) stimulation intensities. This new technique may increase the safety of motor eloquent tumor surgery.
