Purpose: The aim of this study is to investigate the feasibility of recording invasive event-related potentials (iERP) to map language regions in children admitted for pre-surgical invasive stereo-EEG monitoring (SEEG).
Method: This prospective study included 16 children and adolescents with refractory epilepsy aged 5-17 years who were admitted for SEEG monitoring (9 left- and 7 right-sided implantations,
6-19 depth electrodes implanted). In 13 patients the underlying pathology was focal cortical dysplasia (10), tuberous sclerosis (2) and mesial temporal sclerosis (1). Patients completed several language tasks (verb generation, word repetition, listening to reversed words) (recording time on average 60 minutes).
Results: Robust iERP to language stimuli were obtained in all cases, independent of the side of the implantation. Regions around the peri-sylvian cortex were consistently implanted and 5 lateral electrode clusters were formed on an anatomical basis (Inferior frontal gyrus (IFG), subcentral/ frontal operculum (SC/FO), supramarginal/ angular gyrus (SMG/ANG) and superior temporal gyrus (STG)). An early biphasic component (peak at 150-200ms) followed by a sustained negative component was consistently recorded in the STG bilaterally. This cluster showed the highest amplitudes overall (max. -150μV). The SMG/ANG also showed similarities bilaterally with an early negative or positive peak at 150ms and amplitudes of 20-60μV. A lateralising feature was recorded in the IFG, where only the left IFG consistently showed a late positivity (peak: 600-700ms, 50-70μV, duration: 700-900ms), which was not seen in homotopic right IFG recordings.
Conclusion: This work showed that robust iERP can be recorded in response to language stimuli using SEEG. The distribution of language iERP components is compatible with the functional anatomy of the peri-sylvian language system. Language iERP may assist in functional mapping using SEEG of cortical regions under consideration for surgical resection.