Accurate source imaging based on high resolution scalp electroencephalography and individualized finite difference head models in epilepsy pre-surgical workup.

PURPOSE: High-density electroencephalographic source imaging (HD-ESI) has emerged as a useful tool for pre-surgical epilepsy workup. However, it is not routinely used in clinical evaluations due to several factors, one of which is the challenge associated with creating anatomically accurate head models. Reasonable solutions now exist and the present study aims to evaluate the use of these highly resolved individual head models in pre-surgical epilepsy evaluation.

METHODS: Nine patients with intractable epilepsy who were candidates for resective epilepsy surgeries participated in the study. For each patient, 256-channel electroencephalography data were acquired along with individual structural MRI data that was used to construct individual finite difference models (iFDM). Accuracy of HD-ESI based on iFDM (HD-ESI-iFDM) was evaluated using multiple criteria, including concordance with intracranial electroencephalography (icEEG) and location of surgical resection. Performance of HD-ESI-iFDM was also compared against MRI and positron emission tomography (PET) results.

RESULTS: In all but one patient resective surgeries resulted in seizure-free outcome. Source locations derived from HD-ESI-iFDM demonstrated concordance with surgical resection and with icEEG data, when available. The HD-ESI-iFDM also contributed to the planning of intracranial electrodes implantation. Compared to MRI or PET, HD-ESI-iFDM provided more accurate localization of the epileptogenic zone.

CONCLUSION: When acquired with high-density sensor arrays and source imaging is performed with anatomically accurate head models, electroencephalography can contribute meaningfully to epilepsy pre-surgical workup for localization of the epileptogenic zone. Now that both high-density electroencephalography and individualized FDM models can be routinely obtained, it can be incorporated as part of clinical practice.