Article
Threshold-level in transcranial motor evoked potentials during surgery for gliomas close to motor pathway
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Authors
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Tammam Abboud
- Klinik und Poliklinik für Neurochirurgie, Universitätsklinikum Hamburg-Eppendorf
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Miriam Schaper
- Klinik und Poliklinik für Neurochirurgie, Universitätsklinikum Hamburg-Eppendorf
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Cindy Schwarz
- Klinik und Poliklinik für Neurochirurgie, Universitätsklinikum Hamburg-Eppendorf
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Nils Ole Schmidt
- Klinik und Poliklinik für Neurochirurgie, Universitätsklinikum Hamburg-Eppendorf
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Manfred Westphal
- Klinik und Poliklinik für Neurochirurgie, Universitätsklinikum Hamburg-Eppendorf
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Tobias Martens
- Klinik und Poliklinik für Neurochirurgie, Universitätsklinikum Hamburg-Eppendorf
| Published: | June 2, 2015 |
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Outline
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Objective: Warning criteria for monitoring of motor evoked potentials (MEP) after direct cortical stimulation during surgery of supratentorial tumors have been well described. However, little is known about the value of MEP after transcranial electrical stimulation (TES) in predicting postoperative motor deficit when monitoring threshold-level. We aimed to evaluate the feasibility and value of this method in glioma surgery.
Method: Between 10/2013 and 10/2014, 62 patients underwent TES-MEP monitoring during resection of gliomas located close to central motor pathways put not involving the primary motor cortex. MEP were elicited by transcranial repetitive anodal monopolar train-stimulation. Bilateral MEP were continuously evaluated to assess increase of threshold-level (minimum voltage needed to evoke a motor response from each of the muscles being monitored). An increase in threshold-level of more than 20% was considered a warning signal. Recorded alterations were subsequently correlated with postoperative neurological deterioration and MRI findings.
Results: In 3 of 56 patients without preoperative paresis, a permanent increase of more than 20% in threshold-level was observed, all of them showed new paresis postoperatively (transient paresis in 2 patients and permanent paresis in 1 patient).
In 3 of 6 patients with preoperative paresis, a permanent increase of more than 20% in threshold-level was observed, all of them showed postoperative neurological deterioration (transient deterioration in 2 patients and permanent deterioration in 1 patient).
In 56/62 patients, no significant change of threshold-level was detected and except of one patient who developed a new permanent deficit, none of the patients showed postoperative neurological deterioration.
Estimated specificity was 100% and Sensitivity 86.7% (Fisher-Exact test, p≤0.001).
Postoperative MRI revealed gross tumor resection in 60% and subtotal resection in 40% of the patients; territorial ischemia was detected in the one patient with the false negative monitoring finding.
Conclusions: TES-MEP are feasible in glioma surgery. Compared to the reported false negative and false positive results in the literature when using amplitude monitoring, the use of threshold-level in MEP monitoring allows for high specificity and sensitivity.
