Abstracts

Rationale: It has been shown in several studies that high density EEG source imaging (HD-ESI) showed an excellent precision of the epileptic focus localization. We were interested in determining its capacity to localize vital cortex non-invasively with similar precision. We therefore compared localization obtained from ESI of somato-sensory evoked potentials (SEPs) from 128-256 channel scalp EEGs, intracranial SEPs, functional MRI and corticography results. Methods: 5 patients (age 9 - 35 years) with subdural grids over the hemispheric convexity were included in the study. Evoked potentials were obtained by repetitive airpuff stimulation of the thumb. All patients had previous scalp SEPs with 256 electrode scalp EEG, 3 had also fMRI using the same air puff stimuli. In all patients the airpuff stimulation was repeated while being recorded with implanted electrodes. The work-up included electrocorticography to determine motor, sensory and language cortex, using established stimulation parameters. Results: Intracranial SEPs showed cortical components whose gradient and localization was concordant with the corticography results in all patients. Multimodal co-registration of the source of scalp cortical component and the intracranial SEPs was concordant in 4/5 cases. Functional fMRI was slightly displaced in 1 case. Conclusions: Localization of the cortical component of SEPs, with the help of 256 channel EEG recordings, provided precise results in 4/5 patients compared to corticography. HD-ESI showed similar precision than fMRI. Thus, HD-ESI appears to be an interesting alternative to fMRI for those patients who cannot collaborate sufficiently for the fMRI session, e.g. children or patients with mental retardation. Supported by the Swiss National Science Foundation (SPUM consortium 33CM30-124089 and 320030-122073)