Electromagnetic source imaging in presurgical workup of patients with epilepsy: a prospective study

Objective: To determine the diagnostic accuracy and clinical utility of electromagnetic source imaging (EMSI) in presurgical evaluation of patients with epilepsy.
Methods: We prospectively recorded magnetoencephalography (MEG) simultaneously with electroencephalography (EEG) and performed EMSI, comprising electric (ESI), magnetic source imaging (MSI) and analysis of combined MEG-EEG datasets (cEMSI), using two different software packages. As reference standard for irritative zone (IZ) and seizure onset zone (SOZ) we used intracranial recordings and for localization accuracy, outcome one year after operation.
Results: We included 141 consecutive patients. EMSI showed localized epileptiform discharges (ED) in 94 patients (67%). Most of the ED-clusters (72%) were identified by both modalities, 15% only by EEG and 14% only by MEG. Agreement was substantial between inverse solutions and moderate between software packages. EMSI provided new information that changed the management plan in 34% of the patients, and these changes were useful in 80%. Depending on the method, EMSI had a concordance of 53-89% with IZ and 35%-73% with SOZ. Localization accuracy of EMSI was between 44% and 57%, which was not significantly different from MRI (49-76%) and PET (54-85%). cEMSI achieved significantly higher odds ratio compared to ESI and MSI.
Conclusions: EMSI has accuracy similar to established imaging methods and provides clinically useful, new information in 34% of the patients.
Classification of Evidence: This study provides Class IV evidence that EMSI had a concordance of 53-89% and 35%-73% (depending on analysis) for the localization of epilepsy as compared with intracranial recordings - IZ zone and SOZ respectively.

研究目的：明确电磁源成像（electromagnetic source imaging, EMSI）在癫痫患者术前评估中的诊断准确性与临床应用价值。

研究方法：本研究前瞻性同步记录脑磁图（magnetoencephalography, MEG）与脑电图（electroencephalography, EEG），并采用两款不同软件包开展电磁源成像分析，涵盖电生理源成像（electric source imaging, ESI）、磁源成像（magnetic source imaging, MSI）以及联合MEG-EEG数据集分析（cEMSI）。以颅内记录作为激惹区（irritative zone, IZ）与发作起始区（seizure onset zone, SOZ）的参照标准，并以术后1年随访结局作为定位准确性的评估依据。

研究结果：本研究共纳入141例连续性患者。EMSI可在94例（67%）患者中检出局灶性痫样放电（epileptiform discharges, ED）。其中72%的痫样放电簇可通过两种检测模态共同识别，15%仅通过EEG检出，14%仅通过MEG检出。逆解算法之间具有高度一致性，不同软件包之间一致性中等。EMSI可为34%的患者提供可改变诊疗方案的新增信息，且其中80%的方案调整具备临床实用性。根据不同分析方法，EMSI与IZ的契合度为53%~89%，与SOZ的契合度为35%~73%。EMSI的定位准确率介于44%~57%，与MRI（49%~76%）及PET（54%~85%）的定位准确性无显著差异。联合MEG-EEG分析的cEMSI相较于ESI与MSI，具备显著更高的优势比。

研究结论：EMSI的诊断准确性与现有成熟影像学方法相当，且可为34%的患者提供具备临床实用价值的新增诊疗信息。

证据分级：本研究提供IV级证据，表明相较于颅内记录（分别对应IZ与SOZ），EMSI对癫痫灶的定位契合度分别为53%~89%与35%~73%（依分析方法不同而有所差异）。