Multimodal noninvasive evaluation in MRI-negative operculoinsular epilepsy

Abstract

OBJECTIVEPresurgical evaluation of patients with operculoinsular epilepsy and negative MRI presents major challenges. Here the authors examined the yield of noninvasive modalities such as voxel-based morphometric MRI postprocessing, FDG-PET, subtraction ictal SPECT coregistered to MRI (SISCOM), and magnetoencephalography (MEG) in a cohort of patients with operculoinsular epilepsy and negative MRI.METHODSTwenty-two MRI-negative patients were included who had focal ictal onset from the operculoinsular cortex on intracranial EEG, and underwent focal resection limited to the operculoinsular cortex. MRI postprocessing was applied to presurgical T1-weighted volumetric MRI using a morphometric analysis program (MAP). Individual and combined localization yields of MAP, FDG-PET, MEG, and SISCOM were compared with the ictal onset location on intracranial EEG. Seizure outcomes were reported at 1 year and 2 years (when available) using the Engel classification.RESULTSTen patients (45.5%, 10/22) had operculoinsular abnormalities on MAP; 5 (23.8%, 5/21) had operculoinsular hypometabolism on FDG-PET; 4 (26.7%, 4/15) had operculoinsular hyperperfusion on SISCOM; and 6 (30.0%, 6/20) had an MEG cluster (3 tight, 3 loose) within the operculoinsular cortex. The highest yield of a 2-test combination was 59.1%, seen with MAP and SISCOM, followed by 54.5% with MAP and FDG-PET, and also 54.5% with MAP and MEG. The highest yield of a 3-test combination was 68.2%, seen with MAP, MEG, and SISCOM. The yield of the 4-test combination remained at 68.2%. When all other tests were negative or nonlocalizing, unique information was provided by MAP in 5, MEG in 1, SISCOM in 2, and FDG-PET in none of the patients. One-year follow-up was available in all patients, and showed 11 Engel class IA, 4 class IB, 4 class II, and 3 class III/IV. Two-year follow-up was available in 19 patients, and showed 9 class IA, 3 class IB, 1 class ID, 3 class II, and 3 class III/IV.CONCLUSIONSThis study highlights the individual and combined values of multiple noninvasive modalities for the evaluation of nonlesional operculoinsular epilepsy. The 3-test combination of MAP, MEG, and SISCOM represented structural, interictal, and ictal localization information, and constituted the highest yield. MAP showed the highest yield of unique information when other tests were negative or nonlocalizing.

Focal Cortical Dysplasia Type Ⅲ Related Medically Refractory Epilepsy: MRI Findings and Potential Predictors of Surgery Outcome

“…Generally, MRI is the preferred imaging technique for detecting the structural basis of epilepsy [ 9 , 10 ]. In the T2W fluid-attenuated inversion recovery (T2W FLAIR) imaging sequence, the cortical and subcortical hyper-signal is easier to detect [ 11 , 12 ].…”

Fluid and White Matter Suppression Imaging and Voxel-Based Morphometric Analysis in Conventional Magnetic Resonance Imaging-Negative Epilepsy

“…In this study, MAP revealed subtle abnormalities in 64.4% of patients, a finding generally consistent with previous literature ( 17 , 28 , 40 , 41 ). Detection rates of 45% for MRI-negative patients in insular epilepsy ( 42 ), 24.2% in extratemporal lobe epilepsy ( 43 ), 85% in FCD type II ( 24 ), and 43% in a large epilepsy cohort ( 17 ) have been reported using MAP. The slight variation of MAP detection rate among these studies was due to the difference in the definition of “MRI-negative” and the composition of patients included.…”

Optimizing the surgical management of MRI‐negative epilepsy in the neuromodulation era

“…1 About 20% to 40% of adult intractable epilepsy patients have no lesion on MRI, which can portend a poor surgical outcome due to the challenge of seizure onset localization. [2][3][4] There are a number of preoperative predictors of seizure outcome following resective surgery for MRI-negative epilepsy. These include the localization of 18-fluorodeoxyglucose positron emission tomography (FDG-PET) and ictal single-photon positron emission tomography (SPECT) scans, as well as the concordance of multiple diagnostic modalities to a single brain region.…”