Intraoperative Use of nTMS, CCEPs, and DCS for Language Assessment in Brain Tumor Surgery

Overview

This report details a preliminary experience combining navigated Transcranial Magnetic Stimulation (nTMS), Cortico-Cortical Evoked Potentials (CCEPs), and Direct Cortical Stimulation (DCS) for intraoperative language mapping in a patient undergoing awake brain tumor resection. The integration of these modalities demonstrated spatial concordance and reliable identification of language areas, supporting a comprehensive approach to optimize surgical outcomes.

Background

Preservation of language function during neurosurgical tumor resection is critical, with the arcuate fasciculus playing a dominant role in language processing. Awake surgery with bipolar Penfield stimulation remains the gold standard for intraoperative language testing. However, newer technologies such as nTMS and CCEPs have been increasingly utilized to monitor language circuits, even under general anesthesia. Combining these modalities may enhance the safety and efficacy of tumor resections by providing complementary functional and anatomical information.

Data Highlights

Key Findings

• Preoperative nTMS language mapping guided the placement of CCEPs strips and DCS cortical mapping.
• There was a strong spatial correspondence between nTMS-positive spots, DCS-positive sites, and CCEPs recording electrodes, particularly in the pars opercularis of the inferior frontal gyrus and anterior superior temporal gyrus.
• CCEPs demonstrated characteristic evoked potentials (P1 at 7–8 ms, N1 at 20 ms, N2 at 110 ms) when stimulating frontal and recording temporal areas, confirming functional connectivity.
• The average spatial discrepancy among nTMS, DCS, and CCEPs positive points was approximately 5.1 mm, indicating high concordance.
• Awake surgery with integrated multimodal monitoring allowed gross total tumor resection without postoperative language or motor deficits.
• Statistical analysis showed 100% sensitivity, precision, and positive predictive value for the combined mapping approach.

Clinical Implications

Integrating nTMS, CCEPs, and DCS provides a synergistic and reliable method for intraoperative language mapping, potentially improving the safety of tumor resections near eloquent language areas. This multimodal approach may reduce the risk of postoperative language deficits and guide surgical decision-making more precisely, even under awake conditions. The use of nTMS to guide electrode placement for CCEPs and DCS enhances mapping accuracy and efficiency.

Conclusion

The combined use of nTMS, CCEPs, and DCS demonstrates promising concordance in identifying language areas intraoperatively, supporting a comprehensive strategy for brain tumor surgery. Further studies are warranted to validate these findings and refine protocols for broader clinical application.

References

1. Picht et al. 2013 -- Navigated Transcranial Magnetic Stimulation for Preoperative Language Mapping
2. Matsumoto et al. 2004 -- Cortico-Cortical Evoked Potentials in Language Mapping
3. Penfield & Boldrey 1937 -- Somatic Motor and Sensory Representation in the Cerebral Cortex