A Novel Noninvasive Approach Based on SPECT and EEG for the Location of the Epileptogenic Zone in Pharmacoresistant Non-Lesional Epilepsy

Abstract

Background and objectives: The aim of this study is to propose a methodology that combines non-invasive functional modalities electroencephalography (EEG) and single photon emission computed tomography (SPECT) to estimate the location of the epileptogenic zone (EZ) for the presurgical evaluation of patients with drug-resistant non-lesional epilepsy. Materials and Methods: This methodology consists of: (i) Estimation of ictal EEG source imaging (ESI); (ii) application of the subtraction of ictal and interictal SPECT co-registered with MRI (SISCOM) methodology; and (iii) estimation of ESI but using the output of the SISCOM as a priori information for the estimation of the sources. The methodology was implemented in a case series as an example of the application of this novel approach for the presurgical evaluation. A gold standard and a coincidence analysis based on measures of sensitivity and specificity were used as a preliminary assessment of the proposed methodology to localize EZ. Results: In patients with good postoperative evolution, the estimated EZ presented a spatial coincidence with the resection site represented by high values of sensitivity and specificity. For the patient with poor postoperative evolution, the methodology showed a partial incoherence between the estimated EZ and the resection site. In cases of multifocal epilepsy, the method proposed spatially extensive epileptogenic zones. Conclusions: The results of the case series provide preliminary evidence of the methodology’s potential to epileptogenic zone localization in non-lesion drug-resistant epilepsy. The novelty of the article consists in estimating the sources of ictal EEG using SISCOM result as a prior for the inverse solution. Future studies are necessary in order to validate the described methodology. The results constitute a starting point for further studies in order to support the clinical reliability of the proposed methodology and advocate for their implementation in the presurgical evaluation of patients with intractable non-lesional epilepsy.

Nuclear imaging for localization and surgical outcome prediction in epilepsy: A review of latest discoveries and future perspectives

“…The combination of SISCOM with other image modalities provides better EZ localization than using it alone. SISCOM plus EEG source imaging (ESI) showed good localization in TLE (61). From a meta-analysis, SISCOM had moderate sensitivity for EZ localization and gave additional information when MRI is negative (62).…”

Improving surgical outcome with electric source imaging and high field magnetic resonance imaging

“…Also, ictal ESI is less validated with large adequate studies than interictal ESI. Moreover, there is only one small study focusing on MRI-negative epilepsy [131], a subgroup of patients that would highly benefit from localization improvements. Large prospective multi-center studies, as the ongoing European PROMAESIS [132], will help to address these issues.…”

The diagnostic value of ictal SPECT—A retrospective, semiquantitative monocenter study

“…Additionally, the localization precision is improved by mapping the results to the structural MRI image of the subject. 5 , 6 , 17 , 18 Most SPECT studies focus on the concordance of SPECT results and the resected focus in a small cohort of operated individuals, 19 , 20 , 21 , 22 but only few studies have compared VSA and ISAS in a large, unselected cohort.…”