Article
Continuous dynamic mapping to identify the corticospinal tract in motor eloquent brain tumours – experience in 391 cases
Kontinuierliches und dynamisches Mapping der Pyramidenbahn bei motorisch eloquenten Tumoren – Erfahrungen bei 391 Patienten
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Published: | May 8, 2019 |
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Objective: We recently developed a new subcortical mapping technique based on the concept to stimulate the tissue at the site of and synchronously with resection. Our hypothesis was that instead of sequentially performing resection and mapping, a synchronized resection and mapping could potentially improve deficit rates.
Methods: During 8 years, we prospectively included all patients who underwent tumor surgery adjacent to the CST (defined as <1 cm using diffusion tension imaging and fiber tracking) with simultaneous subcortical short train cathodal monopolar mapping, equipped with 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. Motor function was assessed using the Medical Research Council Scale (MRCS; M1–M5) one day after surgery, at discharge, and at 3 months.
Results: Technically, the method was successful in all except one cases (failure rate 0.3%). Lowest individual motor thresholds (MT) reached during resection were as follows (MT, number of patients): >10 mA, n=120; 6–10 mA, n=78; 4–5 mA, n=80; 1–3 mA, n=113. At 3 months, 28 patients (7%) had a persisting postoperative motor deficit, caused by direct mechanical injury in 9 patients (2.3%, 4 of 9 MRCS <M4), vascular injury in 9 patients (2.3%, 6 of 9 MRCS <M4), postoperative bleeding in 2 patients (0.5%, 2 of 2 MRCS <M4) and a residual SMA syndrome in 8 patients (2%, all patients with formal MRCS M5, but fine motor skills deficits). Intraoperative seizures were seen in 1.8% of patients.
Conclusion: 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. This new technique may improve the safety of motor eloquent tumor surgery.