Extraoperative Subdural Grid Electrode Stimulation for Primary Motor Cortex Localization in Medically Intractable
Panu Boontoterm1, Siraruj Sakoolnamarka1, Karanarak Urasyanandana1
1Department of Surgery, Phramongkutklao Hospital, Bangkok, Thailand.
Journal of Epilepsy Research
|June 25, 2026
Summary
Extraoperative cortical stimulation mapping accurately locates the primary motor cortex in epilepsy patients. Younger children require higher stimulation amplitudes, highlighting the need for direct functional mapping.
Area of Science:
- Neurosurgery
- Epileptology
- Neurophysiology
Background:
- Subdural grid electrode (SDE) implantation with cortical stimulation mapping (CSM) is crucial for presurgical evaluation in intractable epilepsy.
- Accurate identification of the primary motor cortex (PMC) is vital to prevent motor deficits, especially in pediatric cases.
Purpose of the Study:
- To assess the clinical utility of extraoperative CSM for PMC localization.
- To investigate factors influencing stimulation amplitude thresholds for PMC mapping.
Main Methods:
- Retrospective review of 297 patients with medically refractory epilepsy undergoing SDE implantation and extraoperative CSM.
- Standardized motor mapping, assessment of postoperative motor outcomes, and correlation with PMC preservation.
- Analysis of associations between stimulation amplitude thresholds and various patient/treatment factors.
Main Results:
- Successful PMC identification in all patients; atypical localization occurred in 11.1%.
- Preservation of mapped PMC correlated with reduced persistent motor deficits.
- Younger age (<7 years) showed an inverse correlation with stimulation amplitude thresholds, even after controlling for antiseizure medication (ASM) burden.
Conclusions:
- Extraoperative CSM with SDEs is a reliable method for PMC localization in epilepsy.
- Functional motor areas can deviate from anatomical landmarks, emphasizing the importance of direct functional mapping.
