Lateralization Of Seizure Focus Research Articles

Shortened Motor Evoked Potential Latency in the Epileptic Hemisphere of Children With Focal Epilepsy.

Motor evoked potential (MEP) amplitude and latency are acquired routinely during neuronavigated transcranial magnetic stimulation, a method of functional mapping of the motor cortex before epilepsy surgery. Although MEP amplitude is routinely used to generate a motor map, MEP latency in patients with focal epilepsy has not been studied systematically. Given that epilepsy may alter myelination, we tested whether intrinsic hand muscle MEPs obtained from the hemisphere containing a seizure focus differ in latency from MEPs collected from the opposite hemisphere. Latencies of abductor pollicis brevis MEPs were obtained during routine motor mapping by neuronavigated transcranial magnetic stimulation in children with intractable, unihemispheric focal epilepsy. The primary motor cortex was stimulated bilaterally in all cases. Only data from patients without a lesion involving the corticospinal tract were included. We tested whether abductor pollicis brevis MEP latency varied as a function of seizure focus lateralization. In the 17 patients who met the inclusion criteria, the mean latency of MEPs with amplitudes in the top and bottom quartiles was shorter in the epileptic hemisphere. Interhemispheric latency difference was greater in patients with lesional epilepsy than in those with nonlesional epilepsy (0.7 ± 0.4 vs. 0.1 ± 0.6 milliseconds, P = 0.02). Motor evoked potential latency was shortened in the epileptic hemisphere of children with focal epilepsy.

Lateralization of interictal temporal lobe hypoperfusion in lesional and non-lesional temporal lobe epilepsy using arterial spin labeling MRI

PurposeNon-invasive imaging studies play a critical role in the presurgical evaluation of patients with drug-resistant temporal lobe epilepsy (TLE), particularly in helping to lateralize the seizure focus. Arterial Spin Labeling (ASL) MRI has been widely used to non-invasively study cerebral blood flow (CBF), with somewhat variable interictal alterations reported in TLE. Here, we compare temporal lobe subregional interictal perfusion and symmetry in lesional (MRI+) and non-lesional (MRI-) TLE compared to healthy volunteers (HVs). MethodsTwenty TLE patients (9 MRI+, 11 MRI-) and 14 HVs under went 3 T Pseudo-Continuous ASL MRI through an epilepsy imaging research protocol at the NIH Clinical Center. We compared normalized CBF and absolute asymmetry indices in multiple temporal lobe subregions. ResultsCompared to HVs, both MRI+ and MRI- TLE groups demonstrated significant ipsilateral mesial and lateral temporal hypoperfusion, specifically in the hippocampal and anterior temporal neocortical subregions, with additional hypoperfusion in the ipsilateral parahippocampal gyrus in the MRI+ and contralateral hippocampus in the MRI- TLE groups. Contralateral to the seizure focus, there was significant relative hypoperfusion in multiple subregions in the MRI- compared to the MRI+ TLE groups. The MRI+ group therefore had significantly greater asymmetry across multiple temporal subregions compared to the MRI- TLE and HV groups. No significant differences in asymmetry were found between the MRI- TLE and HV groups. ConclusionWe found a similar extent of interictal ipsilateral temporal hypoperfusion in MRI+ and MRI- TLE. However, significantly increased asymmetries were found only in the MRI+ group due to differences in perfusion contralateral to the seizure focus between the patient groups. The lack of asymmetry in the MRI- group may negatively impact the utility of interictal ASL for seizure focus lateralization in this patient population.

Atypical intrinsic neural timescales in temporal lobe epilepsy.

Temporal lobe epilepsy (TLE) is the most common pharmacoresistant epilepsy in adults. Here we profiled local neural function in TLE in vivo, building on prior evidence that has identified widespread structural alterations. Using resting-state functional magnetic resonance imaging (rs-fMRI), we mapped the whole-brain intrinsic neural timescales (INT), which reflect temporal hierarchies of neural processing. Parallel analysis of structural and diffusion MRI data examined associations with TLE-related structural compromise. Finally, we evaluated the clinical utility of INT. We studied 46 patients with TLE and 44 healthy controls from two independent sites, and mapped INT changes in patients relative to controls across hippocampal, subcortical, and neocortical regions. We examined region-specific associations to structural alterations and explored the effects of age and epilepsy duration. Supervised machine learning assessed the utility of INT for identifying patients with TLE vs controls and left- vs right-sided seizure onset. Relative to controls, TLE showed marked INT reductions across multiple regions bilaterally, indexing faster changing resting activity, with strongest effects in the ipsilateral medial and lateral temporal regions, and bilateral sensorimotor cortices as well as thalamus and hippocampus. Findings were similar, albeit with reduced effect sizes, when correcting for structural alterations. INT reductions in TLE increased with advancing disease duration, yet findings differed from the aging effects seen in controls. INT-derived classifiers discriminated patients vs controls (balanced accuracy, 5-fold: 76% ± 2.65%; cross-site, 72%-83%) and lateralized the focus in TLE (balanced accuracy, 5-fold: 96% ± 2.10%; cross-site, 95%-97%), with high accuracy and cross-site generalizability. Findings were consistent across both acquisition sites and robust when controlling for motion and several methodological confounds. Our findings demonstrate atypical macroscale function in TLE in a topography that extends beyond mesiotemporal epicenters. INT measurements can assist in TLE diagnosis, seizure focus lateralization, and monitoring of disease progression, which emphasizes promising clinical utility.

Emotional functioning in pediatric epilepsy: Evidence of greater externalizing behavior with left hemisphere onset

Though it is wellknown that psychiatric concerns are common in children with epilepsy, factors predicting such problems are not well understood. The present investigation studied rates of parent-reported psychological concerns in clinically referred children with epilepsy. Further, it investigated differences in psychological distress across epilepsy subtypes (i.e., focal, generalized, mixed), relationships with epilepsy severity variables, gender, and lateralization of seizure foci. The parents of 170 children and adolescents (ages 6–18 years, 78 girls, 92 boys) completed the Child Behavior Checklist (CBCL). Scale elevation frequencies (T-scores ≥ 65) were calculated and Chi square analyses examined rates of elevations between epilepsy groups. Internalizing problems (32.4%) were more common than externalizing problems (17.1%) for the sample, with attention problems being the most common concern across all epilepsy types (48.8%). While there were no significant relationships between epilepsy severity variables and CBCL broadband scales, the Total Problems scale was inversely related to intellectual functioning (r = −0.174, p = 0.023). Rates of anxiety and depression did not differ across epilepsy subtypes and no gender differences were found. Those with left-sided epilepsy had higher rates of externalizing problems (33.2%) than those with right (14.0%; χ2[1, 88] = 4.55, p = 0.03), with rule-breaking behaviors (15.4%) being more common in left-hemisphere epilepsy (15.4% versus 2.3%; χ2[1,88] = 4.66, p = 0.03). In summary, while no significant differences were found across epilepsy groups, the current study adds to the literature regarding lateralization effects and mood/behavior, with more externalizing problems in those with left hemisphere epilepsy.

Comparison of T2 relaxometry and PET CT in the evaluation of patients with mesial temporal lobe epilepsy using video EEG as the reference standard

PurposeOur study aimed to compare the sensitivity of T2 relaxometry and positron emission tomography – computed tomography (PET/CT) in patients with a history suggestive of mesial temporal lobe epilepsy using video electroencephalography (EEG) as the reference standard.Material and methodsIn our study, 35 patients with a history suggestive of mesial temporal lobe epilepsy were subjected to conventional magnetic resonance imaging (MRI), T2 relaxometry, and PET/CT. The results of each of the studies were compared with video EEG findings. Analyses were performed by using statistical software (SPSS version 20.0 for windows), and the sensitivity of conventional MRI, T2 relaxometry, and PET/CT were calculated.ResultsThe sensitivity of qualitative MRI (atrophy and T2 hyperintensity), quantitative MRI (T2 relaxometry), and PET/CT in lateralizing the seizure focus were 68.6% (n = 24), 85.7% (n = 30), and 88.6% (n = 31), respectively.ConclusionsThe sensitivity of MRI in lateralization and localization of seizure focus in temporal lobe epilepsy can be increased by adding the quantitative parameter (T2 relaxometry) with the conventional sequences. T2 Relaxometry is comparable to PET/CT for localization and lateralization of seizure focus and is a useful tool in the workup of TLE patients.

White matter microstructural differences between right and left mesial temporal lobe epilepsy.

Mesial temporal lobe epilepsy (mTLE) is a chronic focal epileptic disorder characterized by recalcitrant seizures often necessitating surgical intervention. Identifying the laterality of seizure focus is crucial for pre-surgical planning. We implemented diffusion MRI (DMRI) connectometry to identify differences in white matter connectivity in patients with left and right mTLE relative to healthy control subjects. We enrolled 12 patients with right mTLE, 12 patients with left mTLE, and 12 age/sex matched healthy controls (HCs). We used DMRI connectometry to identify local connectivity patterns of white matter tracts, based on quantitative anisotropy (QA). We compared QA of white matter to reconstruct tracts with significant difference in connectivity between patients and HCs and then between patients with left and right mTLE. Right mTLE patients show higher anisotropy in left inferior longitudinal fasciculus (ILF) and forceps minor and lower QA in genu of corpus callosum (CC), bilateral corticospinal tracts (CSTs), and bilateral middle cerebellar peduncles (MCPs) compared to HCs. Left mTLE patients show higher anisotropy in genu of CC, bilateral CSTs, and right MCP and decreased anisotropy in forceps minor compared to HCs. Compared to patients with right mTLE, left mTLE patients showed increased and decreased connectivity in some major tracts. Our study showed the pattern of microstructural disintegrity in mTLE patients relative to HCs. We demonstrated that left and right mTLE patients have discrepant alternations in their white matter microstructure. These results may indicate that left and right mTLE have different underlying pathologic mechanisms.

Patterns of brain functional connectivity in frontal and temporal lobe epilepsies

To examine alterations of functional connectivity (FC) of the brain in patients with frontal and temporal lobe epilepsies. Forty-three patients, aged 18-55 years, including 32 with temporal lobe epilepsy (TLE) and 11 with frontal lobe epilepsy (FLE), and 32 age/gender-matched healthy controls (HC) underwent structural and functional MRI on 1,5 T scanner. Imaging data were further analysed for functional connectivity characteristics by seed-based and ICA analyses. Most prominent in the TLE group, was a decrease in FC of insula and peri-insular cortical regions compared to HC. These alterations of FC in left-side TLE were significant on the left. An increase of FC between dorsal part of attention resting network and regions of temporal and parietal cortices characterized right-side TLE. In addition, TLE group had decreased FC between anterior cingulate and basal ganglia. All the significant alterations of FC in FLE related to increased FC in patients compared to HC. FC of temporal regions was altered to a greater extent. Localization and lateralization of seizure focus determines the alterations of brain FC in patients with focal epilepsy.

Comparison of Autonomic Function before and after Surgical Intervention in Patients with Temporal Lobe Epilepsy.

Background and PurposeRefractory temporal lobe epilepsy (TLE) is commonly associated with imbalances in cardiovascular (CV) parasympathetic and sympathetic functions, which are treated using TLE surgery. We investigated the effect of hemispheric lateralization of seizure foci on autonomic CV functions before and after TLE surgery.MethodsThe study was conducted on patients with left TLE (LTLE, n = 23) and right TLE (RTLE, n = 30) undergoing unilateral TLE surgery. To assess the autonomic CV functions, changes in the heart rate (ΔHR) and blood pressure (BP) were measured using a standardized battery of autonomic reactivity tests before surgery and at 3 and 6 months after surgery.ResultsBefore surgery, ΔHR and the expiration to inspiration ratio (E:I) during the deep breathing test were higher in the LTLE group than in the RTLE group (both p < 0.001), but both outcomes were comparable between the groups at 3 and 6 months. ΔHR decreased at 3 and 6 months (p < 0.001 and 0.01, respectively) compared with preoperative values. The E:I at 3 months in the LTLE group was lower (p = 0.04) than the preoperative values. Decrease in systolic BP during the head-up tilt test was greater in the LTLE group than in the RTLE group (p = 0.002) before surgery. The maximum increase in diastolic BP during the cold pressor test was lower in the RTLE group at 6 months than that before surgery (p = 0.001) and in the LTLE group (p = 0.002).ConclusionsWe found that hemispheric lateralization of seizure foci in the temporal lobe had a differential effect on autonomic CV functions before surgery. Before surgery, parasympathetic reactivity was higher in the LTLE group, and sympathetic reactivity was higher in the RTLE group. After surgery, autonomic CV functions were comparable between the groups, suggesting that TLE surgery stabilizes autonomic CV functions.

Attention deficits in children with epilepsy: Preliminary findings.

Attention difficulties are a common clinical complaint among children with epilepsy. We aimed to compare a range of attentional abilities between groups of children with two common epilepsy syndromes, Temporal Lobe Epilepsy (TLE) and Idiopathic Generalized Epilepsy (IGE), and to healthy controls. We also investigated whether epilepsy factors (laterality of seizure focus, epilepsy onset, duration, and severity) were related to attentional abilities. Multiple dimensions of attention (selective, sustained, and divided attention and attentional control) were assessed directly with standardized neuropsychological measures in 101 children aged 6-16years (23 children with TLE, 20 with IGE and 58 healthy controls). Attention was also assessed indirectly, via a parent-report measure. Children with TLE performed worse than children with IGE (p=0.013) and healthy controls (p<0.001) on a test of attentional control, but no between-group differences were apparent on tests of other attentional abilities. Compared to healthy controls, greater attention problems were reported by parents of children with TLE (p=0.006) and IGE (p=0.012). Left-hemisphere seizure focus and greater epilepsy severity were associated with poorer attentional control and sustained-divided attention, respectively, but no other epilepsy factors were associated with attentional abilities. These findings suggest that children with localization-related epilepsy, but not generalized epilepsy, may be at risk of deficits in attentional control. Interventions aimed at improving attentional control may be targeted at children with localization-related epilepsy, particularly those with a left-hemisphere seizure focus, who appear to be particularly susceptible to this type of attentional deficit.

Remembrance and time passed: Memory outcomes 4-11 years after pediatric epilepsy surgery.

Little is known about the long-term cognitive outcomes following pediatric epilepsy surgery. Although the evidence for change within the first 2 years is not compelling, the plasticity of the immature brain may allow for improvements in the long term. This study examined memory function in a cohort of surgical and nonsurgical patients at baseline and 4-11 years after. Participants were 88 patients (mean age 20.05, standard deviation [SD] 4.21 years) with childhood-onset intractable epilepsy; 53 had undergone resective epilepsy surgery. Verbal and visual memory were assessed at baseline and follow-up using standardized tests of recall of stories, faces, word pairs, and word lists. Improvements over time were not found; outcomes were largely independent of surgical status. Those who were seizure-free at follow-up had better story recall at both times (p = 0.028), and did not show improvement. Among patients with extratemporal lobe epilepsy, significant declines in word list recall were found over time irrespective of surgical or seizure status (p = 0.010). Effects of laterality of seizure focus were evident only when examining patients with temporal lobe epilepsy (TLE); patients with left TLE had lower story recall scores compared to patients with right TLE at long-term follow-up (p = 0.043). Patients who became seizure-free had some advantages in memory, but did not show improvements over time. These findings have important implications for understanding potential outcomes from surgery or continued use of antiepileptic medications.

1H-MRS metabolite’s ratios show temporal alternation in temporal lobe seizure: Comparison between interictal and postictal phases

PurposesTo determine 1H-MRSI metabolites changes in interictal and postictal phases of patients suffering from mesial temporal lobe epilepsy with hippocampal sclerosis and lateralization of seizure foci. Materials and methodsMR spectroscopic imaging was performed in 5 adult patients with refractory temporal lobe epilepsy interictally and immediately after the seizure and in 4 adult control subjects. All patients underwent MR imaging and VideoEEG Monitoring. ResultsThe results showed statistically significant decreases in N-acetylaspartate/Creatine, N-acetylaspartate/Choline and N-acetylaspartate/(creatine+choline) immediately after ictus in ipsilateral hippocampus as compared with control data and contralateral hippocampus of patients while no statistically significant difference was presented in interictal phase. ConclusionThe present study clearly indicates 1H-MRS abnormalities following an ictus of temporal lobe epilepsy with metabolite recovery in interictal phase. This finding suggests postictal 1H-MRS as a possible useful tool to assist in lateralizing and localizing of seizure foci in epileptic patients with structural lesions.

Novel assessment of global metabolism by 18F-FDG-PET for localizing affected lobe in temporal lobe epilepsy.

The aim of this study was to develop a novel method of global quantitative analysis for use in the diagnosis and treatment evaluation of temporal lobe epilepsy (TLE). We studied 16 patients diagnosed with TLE who underwent fluorine-18 fluorodeoxyglucose-PET (F-FDG-PET) and MRI at the Hospital of the University of Pennsylvania. To quantify temporal lobe hypometabolism, we averaged the mean standardized uptake value across regions of interest (ROIs) encompassing each lobe in its entirety and calculated the metabolic ratios and lateralization indices for each patient on the basis of global measurements. For comparison, we carried out a traditional 'punch biopsy' ROI analysis by averaging the mean standardized uptake value within 1 cm diameter ROIs across select slices. Both techniques were performed twice by the same rater to test intraobserver variability. An expert observer carried out visual analyses of both F-FDG-PET and MRI for reference. The global quantitative analysis identified a seizure focus lateralization in agreement with clinical evaluations for 91% of patients on both trials, with intraclass correlation coefficients of 0.97 and 0.92 for metabolic ratios and lateralization indices, respectively. The punch biopsy analysis was in agreement for 91 and 82% of patients on respective trials, with intraclass correlation coefficients of 0.90 and 0.75. Expert visual analyses carried out on F-FDG-PET and MRI were in agreement for 64 and 9% of patients, respectively. The global quantitative analysis proved to be the most accurate and reliable of the methods tested. This technique has the potential to improve metabolic analysis in TLE and other neuropsychiatric disorders.

Insights into Intrinsic Brain Networks based on Graph Theory and PET in right- compared to left-sided Temporal Lobe Epilepsy.

The human brain exhibits marked hemispheric differences, though it is not fully understood to what extent lateralization of the epileptic focus is relevant. Preoperative [18F]FDG-PET depicts lateralization of seizure focus in patients with temporal lobe epilepsy and reveals dysfunctional metabolic brain connectivity. The aim of the present study was to compare metabolic connectivity, inferred from inter-regional [18F]FDG PET uptake correlations, in right-sided (RTLE; n = 30) and left-sided TLE (LTLE; n = 32) with healthy controls (HC; n = 31) using graph theory based network analysis. Comparing LTLE and RTLE and patient groups separately to HC, we observed higher lobar connectivity weights in RTLE compared to LTLE for connections of the temporal and the parietal lobe of the contralateral hemisphere (CH). Moreover, especially in RTLE compared to LTLE higher local efficiency were found in the temporal cortices and other brain regions of the CH. The results of this investigation implicate altered metabolic networks in patients with TLE specific to the lateralization of seizure focus, and describe compensatory mechanisms especially in the CH of patients with RTLE. We propose that graph theoretical analysis of metabolic connectivity using [18F]FDG-PET offers an important additional modality to explore brain networks.

Whole-brain MRI phenotyping in dysplasia-related frontal lobe epilepsy.

To perform whole-brain morphometry in patients with frontal lobe epilepsy and evaluate the utility of group-level patterns for individualized diagnosis and prognosis. We compared MRI-based cortical thickness and folding complexity between 2 frontal lobe epilepsy cohorts with histologically verified focal cortical dysplasia (FCD) (13 type I; 28 type II) and 41 closely matched controls. Pattern learning algorithms evaluated the utility of group-level findings to predict histologic FCD subtype, the side of the seizure focus, and postsurgical seizure outcome in single individuals. Relative to controls, FCD type I displayed multilobar cortical thinning that was most marked in ipsilateral frontal cortices. Conversely, type II showed thickening in temporal and postcentral cortices. Cortical folding also diverged, with increased complexity in prefrontal cortices in type I and decreases in type II. Group-level findings successfully guided automated FCD subtype classification (type I: 100%; type II: 96%), seizure focus lateralization (type I: 92%; type II: 86%), and outcome prediction (type I: 92%; type II: 82%). FCD subtypes relate to diverse whole-brain structural phenotypes. While cortical thickening in type II may indicate delayed pruning, a thin cortex in type I likely results from combined effects of seizure excitotoxicity and the primary malformation. Group-level patterns have a high translational value in guiding individualized diagnostics.

The effect of medial temporal lobe epilepsy on visual memory encoding

Effective visual memory encoding, a function important for everyday functioning, relies on episodic and semantic memory processes. In patients with medial temporal lobe epilepsy (MTLE), memory deficits are common as the structures typically involved in seizure generation are also involved in acquisition, maintenance, and retrieval of episodic memories. In this study, we used group independent component analysis (GICA) combined with Granger causality analysis to investigate the neuronal networks involved in visual memory encoding during a complex fMRI scene-encoding task in patients with left MTLE (LMTLE; N=28) and in patients with right MTLE (RMTLE; N=18). Additionally, we built models of memory encoding in LMTLE and RMTLE and compared them with a model of healthy memory encoding (Nenert et al., 2014). For those with LMTLE, we identified and retained for further analyses and model generation 7 ICA task-related components that were attributed to four different networks: the frontal and posterior components of the DMN, visual network, auditory-insular network, and an “other” network. For those with RMTLE, ICA produced 9 task-related components that were attributed to the somatosensory and cerebellar networks in addition to the same networks as in patients with LMTLE. Granger causality analysis revealed group differences in causality relations within the visual memory network and MTLE-related deviations from normal network function. Our results demonstrate differences in the networks for visual memory encoding between those with LMTLE and those with RMTLE. Consistent with previous studies, the organization of memory encoding is dependent on laterality of seizure focus and may be mediated by functional reorganization in chronic epilepsy. These differences may underlie the observed differences in memory abilities between patients with LMTLE and patients with RMTLE and highlight the modulating effects of epilepsy on the network for memory encoding.

Multivariate hippocampal subfield analysis of local MRI intensity and volume: application to temporal lobe epilepsy.

We propose a multispectral MRI-based clinical decision support approach to carry out automated seizure focus lateralization in patients with temporal lobe epilepsy (TLE). Based on high-resolution T1- and T2-weighted MRI with hippocampal subfield segmentations, our approach samples MRI features along the medial sheet of each subfield to minimize partial volume effects. To establish correspondence of sampling points across subjects, we propagate a spherical harmonic parameterization derived from the hippocampal boundary along a Laplacian gradient field towards the medial sheet. Volume and intensity data sampled on the medial sheet are finally fed into a supervised classifier. Testing our approach in TLE patients in whom the seizure focus could not be lateralized using conventional MR volumetry, the proposed approach correctly lateralized all patients and outperformed classification performance based on global subfield volumes or mean T2-intensity (100% vs. 68%). Moreover, statistical group-level comparisons revealed patterns of subfield abnormalities that were not evident in the global measurements and that largely agree with known histopathological changes.

Evaluation of focus laterality in temporal lobe epilepsy: A quantitative study comparing double inversion-recovery MR imaging at 3T with FDG-PET

To quantitatively compare the diagnostic capability of double inversion-recovery (DIR) with F-18 fluorodeoxyglucose positron emission tomography (FDG-PET) for detection of seizure focus laterality in temporal lobe epilepsy (TLE). This study was approved by the institutional review board, and written informed consent was obtained. Fifteen patients with TLE and 38 healthy volunteers were enrolled. All magnetic resonance (MR) images were acquired using a 3T-MRI system. Voxel-based analysis (VBA) was conducted for FDG-PET images and white matter segments of DIR images (DIR-WM) focused on the whole temporal lobe (TL) and the anterior part of the temporal lobe (ATL). Distribution of hypometabolic areas on FDG-PET and increased signal intensity areas on DIR-WM were evaluated, and their laterality was compared with clinically determined seizure focus laterality. Correct diagnostic rates of laterality were evaluated, and agreement between DIR-WM and FDG-PET was assessed using κ statistics. Increased signal intensity areas on DIR-WM were located at the vicinity of the hypometabolic areas on FDG-PET, especially in the ATL. Correct diagnostic rates of seizure focus laterality for DIR-WM (0.80 and 0.67 for the TL and the ATL, respectively) were slightly higher than those for FDG-PET (0.67 and 0.60 for the TL and the ATL, respectively). Agreement of laterality between DIR-WM and FDG-PET was substantial for the TL and almost perfect for the ATL (κ=0.67 and 0.86, respectively). High agreement in localization between DIR-WM and FDG-PET and nearly equivalent detectability of them show us an additional role of MRI in TLE.

α-[ 11 C]-Methyl- l -tryptophan–PET in 191 patients with tuberous sclerosis complex

This was an observational study done on a large cohort of patients with tuberous sclerosis complex (TSC) to determine whether i) the presence of α-[(11)C]-methyl-l-tryptophan (AMT) hotspots is related to the duration of seizure intractability, ii) the presence of AMT hotspots is related to specific TSC gene mutations, and iii) there is concordance between areas with an AMT hotspot and seizure lateralization/localization on scalp EEG. One hundred ninety-one patients (mean age: 6.7 years; median: 5 years; range: 3 months to 37 years) with TSC and intractable epilepsy were included. All patients underwent AMT-PET scan. AMT uptake in each tuber and normal-appearing cortex was measured and correlated with clinical, scalp EEG, and, if available, electrocorticographic data. The longer the duration of seizure intractability, the greater the number of AMT hotspots (r = 0.2; p = 0.03). AMT hotspots were seen in both TSC1 and TSC2. There was excellent agreement in seizure focus lateralization between ictal scalp EEG and AMT-PET (Cohen κ 0.94) in 68 of 95 patients in whom both ictal video-EEG and AMT-PET showed lateralizing findings; in 28 of 68 patients (41%), AMT was more localizing. Furthermore, AMT-PET was localizing in 10 of 17 patients (58%) with nonlateralized ictal EEG. AMT-PET, when used together with video-EEG, provides additional lateralization/localization data, regardless of TSC mutation. The duration of seizure intractability may predict the multiplicity of areas with AMT hotspots.

Presurgical Lateralization of Seizure Focus in Temporal Lobe Epilepsy With Noninvasive Imaging

We retrospectively compared the seizure focus-localizing capability of interictal PET/CT to that of interictal magnetic resonance diffusion-weighted imaging and ictal SPECT in 21 patient candidate for neurosurgery with temporal lobe epilepsy (TLE) by assessing overall lateralizing ability of these modalities and concordance of findings on these studies with results of electroencephalography (EEG). PET/CT demonstrated the greatest lateralizing ability of any of the imaging modalities and had the highest concordance rate for lateralization with EEG, highlighting its increasing diagnostic utility in the preoperative imaging workup of patients with medically intractable TLE.

Anterior temporal lobe white matter abnormal signal (ATLAS) as an indicator of seizure focus laterality in temporal lobe epilepsy: comparison of double inversion recovery, FLAIR and T2W MR imaging

To investigate the diagnostic capability of anterior temporal lobe white matter abnormal signal (ATLAS) for determining seizure focus laterality in temporal lobe epilepsy (TLE) by comparing different MR sequences. This prospective study was approved by the institutional review board and written informed consent was obtained. Three 3D sequences (double inversion recovery (DIR), fluid-attenuated inversion recovery (FLAIR) and T2-weighted imaging (T2WI)) and two 2D sequences (FLAIR and T2WI) were acquired at 3 T. Signal changes in the anterior temporal white matter of 21 normal volunteers were evaluated. ATLAS laterality was evaluated in 21 TLE patients. Agreement of independent evaluations by two neuroradiologists was assessed using κ statistics. Differences in concordance between ATLAS laterality and clinically defined seizure focus laterality were analysed using McNemar's test with multiple comparisons. Pre-amygdala high signals (PAHS) were detected in all volunteers only on 3D-DIR. Inter-evaluator agreement was moderate to almost perfect for each sequence. Correct diagnosis of seizure laterality was significantly more frequent on 3D-DIR than on any other sequences (P ≤ 0.031 for each evaluator). The most sensitive sequence for detecting ATLAS laterality was 3D-DIR. ATLAS laterality on 3D-DIR can be a good indicator for determining seizure focus localization in TLE.