Language mapping in multilingual patients: electrocorticography and cortical stimulation during naming

Area of Science:

• Neuroscience
• Neurosurgery
• Epileptology

Background:

• Epilepsy surgery planning near language cortex is challenging for multilingual patients due to distinct cortical representations for each language.
• Routine electrocortical stimulation mapping (ESM) may not reveal these language-specific differences.
• Electrocorticography (ECoG) offers a potential method to detect functional brain activation through spectral perturbations.

Purpose of the Study:

• To investigate if ECoG, using broadband high gamma augmentation (HGA), can complement ESM in differentiating the cortical representations of first (L1) and second (L2) languages.
• To assess the predictive value of ECoG spectral mapping for post-operative language deficits.

Main Methods:

• Four adult patients with English as a second language underwent ECoG recordings and ESM during visual object naming tasks in L1 and L2.
• Broadband high gamma augmentation (HGA, 60-150 Hz) was used as an index of cortical activation during ECoG.
• Comparison of ECoG findings with ESM results and post-operative language deficits.

Main Results:

• ECoG identified language-specific activated sites in three of four patients that were not detected by ESM.
• Two patients showed greater ECoG HGA during L2 naming, suggesting increased cortical resource recruitment for the second language.
• Post-operative language deficits in three patients were predicted by ECoG spectral mapping but not by ESM.

Conclusions:

• ECoG spectral mapping, particularly HGA, is a valuable tool to complement ESM for pre-surgical language mapping in multilingual patients.
• Evaluating all utilized languages during pre-surgical mapping is crucial to avoid post-operative functional deficits.
• ECoG HGA mapping may help optimize surgical planning by identifying language-specific cortical areas.