A Probabilistic Approach to Functional Organization Based on Extraoperative Electrocortical Stimulation Mapping.

Area of Science:

• Neuroscience
• Neurosurgery
• Epileptology

Background:

• Direct electrocortical stimulation (DES) is crucial for mapping eloquent cortex.
• Existing functional atlases have limitations due to sampling biases and density-based methods.
• Interpatient variability and atypical language areas are poorly understood, especially in epilepsy with functional reorganization.

Purpose of the Study:

• Develop a probabilistic functional atlas using extraoperative DES.
• Characterize the functional organization of language, motor, and sensory cortex.
• Utilize data-driven methods to analyze structure-function relationships.

Main Methods:

• Retrospective observational study of 125 epilepsy patients (2008-2023) undergoing intracranial monitoring.
• Electrical stimulation during language tasks recorded language, motor, and sensory findings.
• Analysis in standard patient space using Human Connectome Project atlas and multilevel statistical framework (probability mapping, bootstrapping, kernel density estimation).

Main Results:

• Eloquent functions are distributed probabilistically, not in discrete regions.
• High interpatient variability in language disruption; middle frontal gyrus identified as a high-probability area for naming and speech arrest.
• Motor responses extended beyond the precentral gyrus; early seizure onset and temporal lobe lesions predicted lower language disruption probability in the temporal lobe.

Conclusions:

• The developed DES atlas serves as a benchmark for functional cortical organization in epilepsy.
• Language and motor systems are more distributed and variable than classically described.
• Individualized mapping is essential for safe neurosurgical planning due to substantial interpatient variability.