Detection of covert lesions in focal epilepsy using computational analysis of multimodal magnetic resonance imaging data.

Baris Kanber,Maria Thom,Daniel C Alexander,Sjoerd B Vos,Roman Rodionov,Gavin P Winston,Fahmida Amin Chowdhury,Jane De Tisi,Tobias C Wood,John S Duncan,Gareth J Barker

doi:10.1111/epi.16836

Abstract

ObjectiveTo compare the location of suspect lesions detected by computational analysis of multimodal magnetic resonance imaging data with areas of seizure onset, early propagation, and interictal epileptiform discharges (IEDs) identified with stereoelectroencephalography (SEEG) in a cohort of patients with medically refractory focal epilepsy and radiologically normal magnetic resonance imaging (MRI) scans.MethodsWe developed a method of lesion detection using computational analysis of multimodal MRI data in a cohort of 62 control subjects, and 42 patients with focal epilepsy and MRI‐visible lesions. We then applied it to detect covert lesions in 27 focal epilepsy patients with radiologically normal MRI scans, comparing our findings with the areas of seizure onset, early propagation, and IEDs identified at SEEG.ResultsSeizure‐onset zones (SoZs) were identified at SEEG in 18 of the 27 patients (67%) with radiologically normal MRI scans. In 11 of these 18 cases (61%), concordant abnormalities were detected by our method. In the remaining seven cases, either early seizure propagation or IEDs were observed within the abnormalities detected, or there were additional areas of imaging abnormalities found by our method that were not sampled at SEEG. In one of the nine patients (11%) in whom SEEG was inconclusive, an abnormality, which may have been involved in seizures, was identified by our method and was not sampled at SEEG.SignificanceComputational analysis of multimodal MRI data revealed covert abnormalities in the majority of patients with refractory focal epilepsy and radiologically normal MRI that co‐located with SEEG defined zones of seizure onset. The method could help identify areas that should be targeted with SEEG when considering epilepsy surgery.

Highlights

Surgical intervention in medically refractory focal epilepsy is only recommended if the area of the brain responsible for seizures can be reliably localized and safely resected
It is noted that the values of dice score coefficient (DSC) should be read with the understanding that a value of 1.0 for DSC requires a perfect overlap between the detected lesional area and the manually drawn abnormality mask
The latter only reflects the extent of the abnormality that is visible on conventional magnetic resonance imaging (MRI) and does not necessarily correspond to the full extent of the epileptogenic lesion

Summary

Introduction

Surgical intervention in medically refractory focal epilepsy is only recommended if the area of the brain responsible for seizures can be reliably localized and safely resected. Recent research has shown that subtle imaging abnormalities that are not evident on visual reading exist in many individuals with MRI-negative epilepsy,3–5 and appropriate image analysis techniques may identify such covert abnormalities, while attempting to balance sensitivity and specificity.6–12 The reliability of these new methods need to be demonstrated[13] before consideration of a clinical trial to evaluate whether their inclusion in the clinical workflow results in a reduction in the number of patients that cannot be offered curative surgery, and an increase in postoperative seizure freedom

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Conclusion