Voxel-based morphometric MRI post-processing in MRI-negative focal cortical dysplasia followed by simultaneously recorded MEG and stereo-EEG

Epilepsy Center, Neurological Institute, Cleveland Clinic Foundation, United States.
Epilepsy research (Impact Factor: 2.02). 03/2012; 100(1-2):188-93. DOI: 10.1016/j.eplepsyres.2012.02.011
Source: PubMed


We aim to report on the usefulness of a voxel-based morphometric MRI post-processing technique in detecting subtle epileptogenic structural lesions. The MRI post-processing technique was implemented in a morphometric analysis program (MAP), in a 30-year-old male with pharmacoresistant focal epilepsy and negative MRI. MAP gray-white matter junction file facilitated the identification of a suspicious structural lesion in the right frontal opercular area. The electrophysiological data by simultaneously recorded stereo-EEG and MEG confirmed the epileptogenicity of the underlying subtle structural abnormality. The patient underwent a limited right frontal opercular resection, which completely included the area detected by MAP. Surgical pathology revealed focal cortical dysplasia (FCD) type IIb. Postoperatively the patient has been seizure-free for 2 years. This study demonstrates that MAP has promise in increasing the diagnostic yield of MRI reading in challenging patients with "non-lesional" MRIs. The clinical relevance and epileptogenicity of MAP abnormalities in patients with epilepsy have not been investigated systematically; therefore it is important to confirm their pertinence by performing electrophysiological recordings. When confirmed to be epileptogenic, such MAP abnormalities may reflect an underlying subtle cortical dysplasia whose complete resection can lead to seizure-free outcome.

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    • "analysis is more sensitive than conventional visual analysis alone (Wagner et al., 2011; Pail et al., 2012; Wang et al., 2012, 2015). "
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    ABSTRACT: Purpose: Focal cortical dysplasias (FCD) type IIb and cortical tubers in tuberous sclerosis complex (TSC) are histopathologically similar and are both epileptogenic lesions frequently causing pharmacoresistant epilepsies. Morphometric analysis of T1- and T2-weighted MRI volume data sets can enhance visualiza- tion of FCD. Here, we retrospectively investigated whether morphometric MRI analysis is of equal benefit for visualizing cortical tubers. Materials and methods: Morphometric analysis was applied to T1- and partly also T2-weighted 1.5 T or 3 T MRI volume data sets of 15 TSC patients using a fully automated MATLAB® script (i.e. MAP07) commonly used for FCD detection. In this study, focus was on the most sensitive of the resulting morphometric feature maps (i.e. the ‘junction image’) which highlights blurring of the gray–white matter junction in comparison to a normal database. The visualization of tubers in these ‘junction images’ was quantitatively compared with that in conventional MR sequences. Results: In all patients, morphometric analysis visualized almost all tubers detected in the normal MRI, and additionally highlighted on average 23% (range 3–50%) more tubers which were not detected by visual analysis of the conventional MR sequences. When T2 volume data sets from a 3 T scanner were available for postprocessing, the rate of additionally detected tubers increased to 29% on average. These formerly overlooked tubers were usually smaller than the tubers already found in the conventional MRI. Conclusion: Morphometric analysis of MRIs in TSC can highlight cortical tubers which are likely to be over- looked in conventional MRI sequences alone. Additionally detected tubers may be of potential importance for both presurgical evaluation and initial diagnosis of TSC.
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    • "Only the confirmed abnormalities were regarded as MAP+. This methodology is consistent with our previous report (Wang et al., 2012) and literature (Wagner et al., 2011). Images for this study were processed and reviewed as part of a large ongoing retrospective study, which examines the sensitivity and specificity of MAP to detect subtle abnormalities in a consecutive cohort of epilepsy patients with a negative MRI. Mixed with patient scans were control scans obtained from normal subjects . "
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    • "MEG is usually evaluated with simultaneouslyrecorded scalp EEG, because both modalities play a complementary role in spike evaluation (Ebersole and Ebersole, 2010). Recently, reports have demonstrated that it is possible to record and analyse simultaneous intracranial EEG and MEG to determine the presence of spikes (Mikuni et al., 1997; Oishi et al., 2002; Santiuste et al., 2008; Wang et al., 2012). "
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    ABSTRACT: Although previous studies have investigated the sensitivity of electroencephalography (EEG) and magnetoencephalography (MEG) to detect spikes by comparing simultaneous recordings, there are no published reports that focus on the relationship between spike dipole orientation or sensitivity of scalp EEG/MEG and the "gold standard" of intracranial recording (stereotactic EEG). We evaluated two patients with focal epilepsy; one with lateral temporal focus and the other with insular focus. Two MEG recordings were performed for both patients, each recorded simultaneously with initially scalp EEG, based on international 10-20 electrode placement with additional electrodes for anterior temporal regions, and subsequently stereotactic EEG. Localisation of MEG spike dipoles from both studies was concordant and all MEG spikes were detected by stereotactic EEG. For the patient with lateral temporal epilepsy, spike sensitivity of MEG and scalp EEG (relative to stereotactic EEG) was 55 and 0%, respectively. Of note, in this case, MEG spike dipoles were oriented tangentially to scalp surface in a tight cluster; the angle of the spike dipole to the vertical line was 3.6 degrees. For the patient with insular epilepsy, spike sensitivity of MEG and scalp EEG (relative to stereotactic EEG) was 83 and 44%, respectively; the angle of the spike dipole to the vertical line was 45.3 degrees. For the patient with lateral temporal epilepsy, tangential spikes from the lateral temporal cortex were difficult to detect based on scalp 10-20 EEG and for the patient with insular epilepsy, it was possible to evaluate operculum insular sources using MEG. We believe that these findings may be important for the interpretation of clinical EEG and MEG.
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