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Updated: Nov 26, 2025
Transcranial Magnetic Stimulation for Investigating Causal Brain-behavioral Relationships and their Time Course
Published on: July 18, 2014
The Relationship Between Stimulation Current and Functional Site Localization During Brain Mapping
Rachel H Muster1, Jacob S Young2, Peter Y M Woo2
1School of Medicine, University of California, San Francisco, San Francisco, San Francisco, California.
Background:
Gliomas are often in close proximity to functional regions of the brain; therefore, electrocortical stimulation (ECS) mapping is a common technique utilized during glioma resection to identify functional areas. Stimulation-induced seizure (SIS) remains the most common reason for aborted procedures. Few studies have focused on oncological factors impacting cortical stimulation thresholds.
Objective:
To examine oncological factors thought to impact stimulation threshold in order to understand whether a linear relationship exists between stimulation current and number of functional cortical sites identified.
Methods:
We retrospectively reviewed single-institution prospectively collected brain mapping data of patients with dominant hemisphere gliomas. Comparisons of stimulation threshold were made using t-tests and ANOVAs. Associations between oncologic factors and stimulation threshold were made using multivariate regressions. The association between stimulation current and number of positive sites was made using a Poisson model.
Results:
Of the 586 patients included in the study, SIS occurred in 3.92% and the rate of SIS events differed by cortical location (frontal 8.5%, insular 1.6%, parietal 1.3%, and temporal 2.8%; P = .009). Stimulation current was lower when mapping frontal cortex (P = .002). Stimulation current was not associated with tumor plus peritumor edema volume, world health organization) (WHO grade, histology, or isocitrate dehydrogenase (IDH) mutation status but was associated with tumor volume within the frontal lobe (P = .018). Stimulation current was not associated with number of positive sites identified during ECS mapping (P = .118).
Conclusion:
SISs are rare but serious events during ECS mapping. SISs are most common when mapping the frontal lobe. Greater stimulation current is not associated with the identification of more cortical functional sites during glioma surgery.
Insights
Stimulation-induced seizures during glioma surgery are rare but more common in the frontal lobe. Higher electrical stimulation current does not identify more functional brain sites during surgery.
Area of Science:
- Neurosurgery
- Neuro-oncology
- Brain Mapping
Background:
- Gliomas often require electrocortical stimulation (ECS) mapping to identify functional brain areas during resection.
- Stimulation-induced seizures (SIS) are the primary cause for aborting glioma resection procedures.
- Oncological factors influencing cortical stimulation thresholds are not well-studied.
Purpose of the Study:
- To investigate oncological factors affecting stimulation thresholds during ECS mapping for gliomas.
- To determine if stimulation current correlates linearly with the number of identified functional cortical sites.
Main Methods:
- Retrospective review of prospectively collected brain mapping data from patients with dominant hemisphere gliomas.
- Statistical analysis including t-tests, ANOVAs, multivariate regressions, and Poisson models.
- Comparison of stimulation thresholds based on oncological factors and tumor characteristics.
Main Results:
- Stimulation-induced seizures occurred in 3.92% of cases, with higher rates in the frontal lobe (8.5%).
- Lower stimulation current was observed when mapping the frontal cortex.
- Tumor volume in the frontal lobe was associated with stimulation current, but WHO grade, IDH mutation, histology, or edema volume were not.
Conclusions:
- Stimulation-induced seizures are infrequent but significant complications during ECS mapping, particularly in the frontal lobe.
- Increased stimulation current does not correlate with identifying a greater number of functional cortical sites during glioma surgery.
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