Magnetic source imaging in non-lesional neocortical epilepsy: Additional value and comparison with ICEEG

ObjectiveTo investigate the utility of magnetic source imaging (MSI) for localizing the epileptogenic zone (EZ) and predicting epilepsy surgery outcome in non-lesional neocortical focal epilepsy (NLNE) patients.MethodsData from 18 consecutive patients with NLNE who underwent presurgical evaluation including intracranial electroencephalography (ICEEG) and MSI were studied. Follow-up after epilepsy surgery was ≥ 24 months. Intracranial electroencephalography and MSI results were classified using a sublobar classification.ResultsSublobar ICEEG focus was completely resected in 15 patients; seizure-free rate was 60%. Eight patients showed sublobar-concordant ICEEG/MSI results and complete resection of both regions; seizure-free rate was 87.5%. Seizure-free rate in cases not matching these criteria was only 30% (p = 0.013).ConclusionsMagnetoencephalography is a useful tool to localize the EZ and determine the site of surgical resection in NLNE patients. When sublobar concordance with ICEEG is observed, MSI increases the predictive value for a seizure-free epilepsy surgery outcome in these patients.

► We investigate Magnetic Source Imaging (MSI) in the presurgical evaluation of non-lesional neocortical epilepsies. ► MSI provides useful additional information compared to Intracranial EEG (ICEEG) alone. ► MSI is useful to localize the epileptogenic zone in these patients. ► Sublobar concordance of ICEEG/MSI results increases the predictive value for a seizure-free surgical outcome.