Bilateral Temporal Lobe Epilepsy Research Articles

Hippocampal high frequency oscillations in unilateral and bilateral mesial temporal lobe epilepsy

ObjectiveThe main aim of this study was to investigate the potential differences in terms of interictal high frequency oscillations (HFOs) between both hippocampi in unilateral (U-MTLE) and bilateral mesial temporal lobe epilepsy (B-MTLE). MethodsSixteen patients with MTLE underwent bilateral hippocampal depth electrode implantation as part of epilepsy surgery evaluation. Interictal HFOs were detected automatically. The analyses entail comparisons of the rates and spatial distributions of ripples and fast ripples (FR) in hippocampi and amygdalae, with respect to the eventual finding of hippocampal sclerosis (HS). ResultsIn U-MTLE, higher ripple and FR rates were found in the hippocampi ipsilateral to the seizure onset than in the contralateral hippocampi. Non-epileptic hippocampi in U-MTLE were distinguished by significantly lower ripple rate than in the remaining analyzed hippocampi. There were not differences between the hippocampi in B-MTLE. In the hippocampi with proven HS, higher FR rates were observed in the ventral than in the dorsal parts. ConclusionsNon-epileptic hippocampi in U-MTLE demonstrated significantly lower ripple rates than those epileptic in U-MTLE and B-MTLE. SignificanceLow interictal HFO occurrence might be considered as a marker of the non-epileptic hippocampi in MTLE.

The methylation status of NKCC1 and KCC2 in the patients with refractory temporal lobe epilepsy.

Methylation is a key epigenetic modification of DNA and regarding its impact on epilepsy, it is argued that "DNA methylation may play an important role in seizure susceptibility and maintenance of the disorder". DNA methylation status of KCC2 (SCL12A5) and NKCC1 (SCL12A2) associated with refractory temporal lobe epilepsy was investigated in our study. Thirty-eight patients with temporal lobe epilepsy (TLE) who were diagnosed by video EEG monitoring and 32 healthy control subjects were included in the study. Twenty-three patients in TLE group were men and the remaining 15 were women. Among them, 27 had unilateral temporal focus (9 with right; 18 with left) and 11 patients had bilateral TLE. We analyzed promoter region methylation status of the KCC2 (SCL12A5) and NKCC1 (SCL12A2) genes in the case and control groups. Gene regions of interest were amplified through PCR and sequencing was accomplished with pyro-sequencing. We found a significant relationship between TLE and methylation on the NKCC1. However, there was no association between TLE and methylation on the KCC2 gene. Also, we found no association between right or left and unilateral or bilateral foci of TLE. There was no relationship between TLE and methylation on the NKCC1and KCC2 genes in terms of mesial temporal sclerosis in cranial MRI, head trauma or febrile convulsions. The methylation of NKCC1 can be a mecha-nism of refractory temporal lobe epilepsy. There are limited findings about DNA methylation in TLE. Therefore, further studies with large sample sizes are necessary.

T09. Seizure detection in temporal lobe epileptic patients using multi-modal fNIRS/EEG recordings

Introduction In recent years, multi-modal approaches have emerged integrating functional near-infrared spectroscopy (fNIRS) with electroencephalography (EEG) to offer dual hemodynamic and electro-potential characterization of a seizure event. Herein, we employ deep learning methods such as the recurrent neural network (RNN) with long short- term memory (LSTM) cell as it is well suited for sequential data to propose a novel means of seizure detection. Methods We designed a deep RNN-LSTM and used as input multi-modal data from 40 patients between the ages of 22–70 years of age suffering from recalcitrant bilateral temporal lobe epilepsy. Prior consent was obtained before recordings were performed in the epilepsy monitoring unit of Notre Dame Hospital, Montreal, Canada. For each recording, distinct seizure and non-seizure classes were partitioned. Initially, EEG data only was used as input into the RNN-LSTM, followed by multi-modal data. Results Through extensive hyper-parameter optimization and data regularization techniques, we show that multi-modal EEG-fNIRS data provides superior performance metrics in a seizure detection task with low generalization error and loss with sensitivity and specificity of 90%, 96% respectively as compared to EEG alone, with sensitivity and specificity of 82% and 90% respectively. The hemodynamic response to seizure non-routinely appeared prior to electrical discharges; thereby indicating cerebral oxygenation parameters are possible seizure harbinger. Conclusion These results exemplify the enhanced detection value of multi-modal neuroimaging, particularly fNIRS, in epileptic patients. Furthermore, the neural network models proposed and characterized herein offer a promising framework for future multi-modal EEG-fNIRS investigations in precocious seizure detection.

The surgical outcome of patients with bilateral temporal lobe epilepsy

ObjectivesThe purpose of this study is to explore the surgical outcome of unilateral anterior temporal lobectomy (ATL) for patients with bilateral temporal lobe epilepsy (BTLE). MethodsWe retrospectively reviewed the data of patients who were diagnosed with BTLE by scalp electroencephalogram (EEG) and underwent ATL from 2001 to 2015. In addition, 80 patients were randomly selected as a control group. ResultsOne hundred seventeen patients were included in this study and were divided into four groups by intracranial recordings as follows: 78 patients with unilateral seizure onset (Group 1), 13 patients with lateralizable dominant seizure onset (Group 2), 14 patients with lateralizable neuroimaging abnormalities (Group 3), and 12 patients without lateralizable dominant seizure onset or neuroimaging abnormalities (Group 4). The 12 patients in Group 4 declined surgical resection, whereas the remaining 105 patients received ATL, and 93 of them were followed up for more than 1 year after surgery. At the 1-, 2-, and 3-year follow-ups the percentage of patients who were seizure free was 52.9%, 56.5%, and 58.9%, respectively. For the mean postoperative efficacy, there was a statistical difference in patients who were seizure free either between Group 1 + Group 2 + Group 3 and the control group (44.1% vs. 67.5%, p = 0.002), or between Group 1 and the control group (48.5% vs. 67.5%, p = 0.019), or between Group 2 + Group 3 and the control group (32.0% vs. 67.5%, p = 0.002). However, the difference was significant only at the first year follow-up, and there was no significant difference afterward. SignificanceAlthough the surgical outcome of patients with BTLE is not as good as that of patients with unilateral TLE in short-term follow-up, quite a portion of these patients could benefit from unilateral temporal lobe resection in the long term.

Accuracy and Efficacy for Robotic Assistance in Implanting Responsive Neurostimulation Device Electrodes in Bilateral Mesial Temporal Lobe Epilepsy.

Responsive neurostimulation (RNS) is a relatively new treatment option that has been shown to be effective for patients with medically refractory focal epilepsy when resection is not possible, especially in bilateral mesial temporal onset. Robotic devices are becoming increasingly popular for use in stereotactic procedures such as stereoelectroencephalography, but have yet to be used when implanting RNS devices. To show that these 2 forms of advanced technology were compatible and could be used effectively in patient care. We implanted RNS devices in 3 patients with bilateral mesial temporal lobe epilepsy. Each patient was placed in the prone position, and electrode trajectories were planned via the robotic navigation system via a transoccipital approach. One lead was placed along each amygdalohippocampal complex. A small craniectomy was then created in the parietal region for RNS generator implantation. Actual and expected target locations and distance were calculated for each depth. There were no complications in this group. RNS devices with bilateral leads were successfully implanted in all 3 patients, with bilateral mesial temporal lobe onset. Follow-up ranged from 3 to 6 mo, and there were no complications in this group. The median distance between the estimate and actual targets was 2.18 (range = 1.11-3.27) mm. We show that implanting RNS devices with robotic assistance is feasible with excellent precision and accuracy. The advantages of using robotic assistance include higher flexibility, accuracy, precision, and consistency.

An SEEG study of bilateral temporal lobe epilepsy suggested by scalp EEG

Objective To explore the lateralizing value of stereotactic electroencephalography (SEEG) in bilateral temporal lobe epilepsy (BTLE) suggested by scalp EEG and to assess the surgical outcomes. Methods A retrospective study was conducted on the clinical features and SEEG monitoring results of 10 patients who were diagnosed as BTLE based on scalp EEG and underwent SEEG implantation from January 2014 to December 2015 at Renji Hospital, School of Medicine, Shanghai Jiaotong University. According to the SEEG results, anterior temporal lobectomy with amygdalohippocampectomy (ATL-AH) was performed for unilateral temporal lobe epilepsy (UTLE) and BTLE with unilaterally dominant epileptic focus, and neuromodulation was performed for BTLE without unilaterally dominant epileptic focus. Results SEEG monitoring data revealed UTLE in 7 out of the 10 patients and BTLE in the other 3 patients including 1 with unilaterally dominant epileptic focus. Among the 8 patients undergoing ATL-AH, 6 patients were classified as Engel I and 2 as Engel Ⅱ post surgery. Neuromodulation was performed in 2 patients and both reported an Engel class III outcome. Conclusions In patients with BTLE suggested by scalp EEG, unilateral onset might be identified in most cases which could achieve good surgical outcomes following ATL-AH. SEEG seems to be a safe and effective method to lateralize BTLE as indicated by scalp EEG. Patients with UTLE and BTLE with unilaterally dominant epileptic focus could obtain good outcomes (Engel class I and II) post ATL-AH. Moreover, neuromodulation seems to be an effective therapy for BTLE without unilaterally dominant epileptic focus. Key words: Epilepsy, temporal lobe; Stereoelectroencephalography; Neurosurgical procedures; Evaluation studies

Stereotactic bilateral transfrontal minimal radiofrequency thermocoagulation of the amygdalohippocampal complex for bilateral medial temporal lobe epilepsy: a retrospective study of 12 patients.

Some patients with temporal lobe epilepsy have bilateral discharges and a few have bilateral medial temporal sclerosis. Stereotactic bilateral radiofrequency thermocoagulation (RFTC) of the amygdalohippocampal complex can terminate seizures or reduce seizure severity in patients with bilateral medial temporal lobe epilepsy (BMTLE). To explore the safety and efficacy of bilateral transfrontal minimal RFTC of the amygdalohippocampal complex for the treatment of BMTLE. A total of 12 BMTLE patients were treated with bilateral transfrontal minimal RFTC of the amygdalohippocampal complex under limited coagulations. The volumes of coagulated lesions were less than 0.6cm3 Clinical outcomes were evaluated using Engel's classification, the Liverpool Seizure Severity Scale (LSSS) 2.0, Wechsler Adult Intelligence Scale-Revised (WAIS-R), and Wechsler Memory Scale-Revised (WMS-R). Quality of life (QOL) was evaluated using the 36-item Short Form Health Survey (SF-36). Of the 12 patients, five (42%) were assessed as Engel Class I during 12-62 months of follow-up. LSSS scores declined sharply compared with the baseline of patients not in the seizure-free category. Functions of memory and intelligence declined transiently without statistical significance (p>0.05) immediately after surgery, but improved significantly (p<0.05) six months later. The qualities of life improved except vitality. Bilateral transfrontal minimal RFTC of the amygdalohippocampal complex may terminate seizures or reduce seizure severity in patients with BMTLE. Under limited coagulations, neuropsychological function was not affected but improved along with seizure control.

Mismatch negativity is abnormal but not lateralizing in temporal lobe epilepsy.

We investigated the changes of mismatch negativity (MMN) in patients with temporal lobe epilepsy (TLE) and explored the possible role of MMN in lateralizing their seizure focus. Thirty patients with TLE and thirty healthy controls were included. MMN was elicited in each subject. Patients with TLE were divided into three subgroups: unilateral left TLE; unilateral right TLE, and bilateral TLE. MMN amplitudes and latencies were compared between the patients with TLE and the control group, and also among the three subgroups of TLE, using repeated measures analyses of variance (ANOVA). To assess the lateralizing value of MMN, MMN latencies and amplitudes at the mastoid sites between the ipsilateral and contralateral sides of epileptic focus in patients with unilateral TLE were compared using t-test. Compared with controls, each subgroup of patients with TLE had longer latencies of MMN at both fronto-central and mastoid sites, but the amplitudes of MMN were not significantly different. The amplitudes and latencies of MMN were not significantly different between the ipsilateral and contralateral sides of seizure focus at mastoid sites. The present findings of prolonged latencies of MMN are suggestive of cognitive impairment in TLE. Both the mastoid sites and the fronto-central sites are involved, which likely reflect widespread cortical abnormalities in TLE. However, the changes of MMN during the interictal phase are not useful for lateralizing the seizure focus in patients with TLE.

Contralateral Hippocampal Stimulation for Failed Unilateral Anterior Temporal Lobectomy in Patients with Bilateral Temporal Lobe Epilepsy

Aims: To prospectively study the surgical outcomes of unilateral anterior temporal lobectomy (ATL) in patients with intractable bilateral temporal lobe epilepsy (TLE) as well as two-staged contralateral hippocampal stimulation in patients after failed unilateral ATL. Methods: Eighteen carefully selected patients with bilateral TLE underwent unilateral ATL. Five cases with failed ATL underwent two-staged contralateral hippocampal stimulation. Seizure control and changes in intelligence quotient (IQ), memory quotient, and quality of life (QOL) were analyzed 2-5 years after treatment. Results: In the patients with unilateral ATL, the percentages seizure free were 55.6% (10/18), 50.0% (9/18), and 44.4% (4/9) at the 1-, 2-, and 5-year follow-up visits, respectively. There were significant difference in seizure control between the patients with unilateral ATL and the 12 cases in the medication group. Significant differences were also found in changes in the patients' QOL and full-scale IQ at the 2-year follow-up between the surgical and medication groups. Five patients who underwent contralateral hippocampal stimulation after failed unilateral ATL experienced 80-100% seizure reductions, and 80% were seizure free 1 year after hippocampal stimulation. Conclusion: Unilateral ATL provides good seizure control and does not cause serious memory or IQ injury in carefully selected patients with true bilateral TLE. Contralateral hippocampal stimulation is a useful approach for patients who experience unilateral ATL failure.

Interictal serum brain-derived neurotrophic factor level reflects white matter integrity, epilepsy severity, and cognitive dysfunction in chronic temporal lobe epilepsy.

Most patients with temporal lobe epilepsy (TLE) have epileptic foci originating from the medial temporal lobe, particularly the hippocampus. Brain-derived neurotrophic factor (BDNF) is a member of the neurotrophin growth factor mainly expressed in the hippocampus, though it is not known whether the circulating level of BDNF reflects cognitive performance or white matter structural changes in chronic TLE. Thirty-four patients with TLE and 22 healthy controls were enrolled for standardized cognitive tests, diffusion tensor imaging, and serum BDNF measurement. The patients were further divided into a subgroup with unilateral TLE (n=23) and a subgroup with bilateral TLE (n=11) for clinical and neuroimaging comparisons. There were significantly lower BDNF levels in the patients with TLE compared with the controls, with significance contributed mainly from the subgroup with bilateral TLE, which also had more frequent seizures. The BDNF levels correlated with epilepsy duration (σ=-0.355; p=0.040) and fractional anisotropy (FA) in the left temporal lobe, left thalamus, and right hippocampus. Using a regression model, BDNF level predicted verbal memory score. Further, design fluency scores were predicted by serum BDNF level via the interactions with left temporal FA. Serum BDNF levels reflected longer epilepsy duration, impaired white matter integrity, and poor cognitive function in patients with chronic TLE.

H-coil repetitive transcranial magnetic stimulation for treatment of temporal lobe epilepsy: A case report.

Low frequency repetitive TMS (rTMS) of a cortical seizure focus is emerging as an antiepileptic treatment. While conventional rTMS stimulators activate only superficial cortical areas, reaching deep epileptic foci, for example in temporal lobe epilepsy (TLE), is possible using specially designed H-coils. We report the results of rTMS in a young adult with pharmacoresistant bilateral TLE who underwent three courses (of 10, 15, and 30 daily sessions) of unilateral rTMS over the hemisphere from which seizures originated most often. Seizure frequency was assessed before and after each block of rTMS sessions, as was the tolerability of the procedure. Seizure frequency declined significantly, by 50 to 70% following each rTMS course. All sessions were well-tolerated.

DTI-based response-driven modeling of mTLE laterality.

PurposeTo develop lateralization models for distinguishing between unilateral and bilateral mesial temporal lobe epilepsy (mTLE) and determining laterality in cases of unilateral mTLE.BackgroundmTLE is the most common form of medically refractory focal epilepsy. Many mTLE patients fail to demonstrate an unambiguous unilateral ictal onset. Intracranial EEG (icEEG) monitoring can be performed to establish whether the ictal origin is unilateral or truly bilateral with independent bitemporal ictal origin. However, because of the expense and risk of intracranial electrode placement, much research has been done to determine if the need for icEEG can be obviated with noninvasive neuroimaging methods, such as diffusion tensor imaging (DTI).MethodsFractional anisotropy (FA) was used to quantify microstructural changes reflected in the diffusivity properties of the corpus callosum, cingulum, and fornix, in a retrospective cohort of 31 patients confirmed to have unilateral (n = 24) or bilateral (n = 7) mTLE. All unilateral mTLE patients underwent resection with an Engel class I outcome. Eleven were reported to have hippocampal sclerosis on pathological analysis; nine had undergone prior icEEG. The bilateral mTLE patients had undergone icEEG demonstrating independent epileptiform activity in both right and left hemispheres. Twenty-three nonepileptic subjects were included as controls.ResultsIn cases of right mTLE, FA showed significant differences from control in all callosal subregions, in both left and right superior cingulate subregions, and in forniceal crura. Comparison of right and left mTLE cases showed significant differences in FA of callosal genu, rostral body, and splenium and the right posteroinferior and superior cingulate subregions. In cases of left mTLE, FA showed significant differences from control only in the callosal isthmus. Significant differences in FA were identified when cases of right mTLE were compared with bilateral mTLE cases in the rostral and midbody callosal subregions and isthmus. Based on 11 FA measurements in the cingulate, callosal and forniceal subregions, a response-driven lateralization model successfully differentiated all cases (n = 54) into groups of unilateral right (n = 12), unilateral left (n = 12), and bilateral mTLE (n = 7), and nonepileptic control (23).ConclusionThe proposed response-driven DTI biomarker is intended to lessen diagnostic ambiguity of laterality in cases of mTLE and help optimize selection of surgical candidates. Application of this model shows promise in reducing the need for invasive icEEG in prospective cases.

Olfactory abnormalities in temporal lobe epilepsy

We studied olfactory function in a cohort of 25 temporal lobe epilepsy (TLE) patients and 25 healthy controls. Our objectives were to measure olfactory acuity in patients with right, left or bilateral TLE and compare them with age and sex matched controls, and to correlate olfactory acuity with duration of seizure, baseline seizure control and the number of drugs used. Olfactory impairment is common in neurological disorders and dysfunction of the temporo-limbic neural substrates involved in olfactory perception is noted in TLE. We measured olfactory acuity in 25 patients with TLE, nine with right, 10 with left and six with bilateral temporal lobe seizure activity, and compared them to the controls. Odor identification was assessed using the University of Pennsylvania Smell Identification Test (UPSIT) which is a 40 item olfactory test used to diagnose olfactory deficits. Our results showed that patients with TLE exhibited significant impairment in UPSIT performance compared to the controls. There was no significant difference in scores between the right and left TLE patients. The severity of olfactory impairment did not correlate with the duration of seizures, baseline seizure control and number of drugs used. We concluded that significant olfactory impairment is seen in both right and left TLE patients, unrelated to the duration and baseline frequency of seizures or drugs used.

MRI characterization of temporal lobe epilepsy using rapidly measurable spatial indices with hemisphere asymmetries and gender features

The paucity of morphometric markers for hemispheric asymmetries and gender variations in hippocampi and amygdalae in temporal lobe epilepsy (TLE) calls for better characterization of TLE by finding more useful prognostic MRI parameter(s). T1-weighted MRI (3 T) morphometry using multiple parameters of hippocampus-parahippocampus (angular and linear measures, volumetry) and amygdalae (volumetry) including their hemispheric asymmetry indices (AI) were evaluated in both genders. The cutoff values of parameters were statistically estimated from measurements of healthy subjects to characterize TLE (57 patients, 55% male) alterations. TLE had differential categories with hippocampal atrophy, parahippocampal angle (PHA) acuteness, and several other parametric changes. Bilateral TLE categories were much more prevalent compared to unilateral TLE categories. Female patients were considerably more disposed to bilateral TLE categories than male patients. Male patients displayed diverse categories of unilateral abnormalities. Few patients (both genders) had combined bilateral appearances of hippocampal atrophy, amygdala atrophy, PHA acuteness, and increase in hippocampal angle (HA) where medial distance ratio (MDR) varied among genders. TLE had gender-specific and hemispheric dominant alterations in AI of parameters. Maximum magnitude of parametric changes in TLE includes (a) AI increase in HA of both genders, (b) HA increase (bilateral) in female patients, and (c) increase in ratio of amygdale/hippocampal volume (unilateral, right hemispheric), and AI decrease in MDR, in male patients. Multiparametric MRI studies of hippocampus and amygdalae, including their hemispheric asymmetry, underscore better characterization of TLE. Rapidly measurable single-slice parameters (HA, PHA, MDR) can readily delineate TLE in a time-constrained clinical setting, which contrasts with customary three-dimensional hippocampal volumetry that requires many slice computation.

Intracranial electrographic analysis of preictal spiking and ictal onset in uni- and bitemporal epilepsy.

Ictal onset patterns in bilateral mesial temporal lobe epilepsy have not been comprehensively studied. A retrospective review of intracranial electrographic data was undertaken to establish whether it is possible to distinguish between unilateral and bilateral mesial temporal lobe epilepsy based on ictal onset patterns, including periodic preictal spiking. A total of 470 ictal onset patterns were analyzed by bitemporal extraoperative electrocorticography in 13 patients with medically intractable mesial temporal lobe epilepsy. Ictal onset patterns were categorized, by frequency, as type A (<12 Hz), type B (12-40 Hz) and type C (>40 Hz). Preictal rhythmic spiking, of at least five seconds duration, and time to contralateral propagation were also measured with each ictal event. We determined if the proportion of "ictal onset pattern frequencies" or "incidence of preictal spiking" differed between unilateral and bilateral mesial temporal lobe epilepsy. Seven patients with unilateral mesial temporal lobe epilepsy received surgery and achieved Engel class I outcomes, while the remaining six did not undergo resective surgery, due to the bilateral ictal onsets in extraoperative electrocorticography. The proportion of patients experiencing any preictal spikes was higher in unitemporal than in bitemporal cases (100% vs 50%;p=0.069). Ofthe470 ictal onset patterns analyzed (174 unitemporal and 296 bitemporal), a significant greater percentage of preictal spikes was found in unilateral cases (78% unitemporal vs 14% bitemporal; p=0.002). Low-frequency patterns were more evident in bitemporal cases (45%) than in unitemporal (10%), although the difference was not statistically significant (p=0.129). No differences were detected between the unitemporal and bitemporal groups regarding age at onset or at presentation. A greater proportion of pre ictal spiking, based on extraoperative electrocorticography, was present in unilateral, compared to bilateral, mesial temporal lobe epilepsy. Further studies are warranted to determine the causal significance of preictal spiking in mesial temporal lobe epilepsy.

Concordance rate between Wada and fMRI tests for visual memory assessment of patients with medically intractable temporal lobe epilepsy

Background: There is not enough evidence to prove either invasive Wada or non-invasive fMRI test predicts postoperative memory changes more accurately in patients with refractory temporal lobe epilepsy (TLE). In this study, concordance between fMRI and Wada test for postoperative assessment of visual memory is investigated. Methods: fMRI test with a novel scene-encoding task were conducted on our cohort of patients. fMRI laterality indices (LI) were then defined as a ratio (L-R)/(L+R) between the number of activated voxels in the left and right of two regions: hippocampus+parahippocampus (Region A) and temporal lobe - (hippocampus+parahippocampus) (Region B). fMRI results were divided into the right (LI &lt; -0.2), left (LI &gt; 0.2) or bilateral (-0.2 &lt; LI &lt;0.2) hemispheric memory dominance and compared to the results of the Wada test. Results: 19 patients were studied (14 left TLE, 3 right TLE and 2 bilateral TLE). The concordance rate between Wada and fMRI tests was 36.8% and 42.1% for regions A and B. Conclusions: Based on the results, the concordance rate between the Wada test and the fMRI test is not high. As a future work, we will investigate the correlation of each test to postoperative memory outcome.

The Risk-Benefit Ratio for Temporal Lobe Resection in Patients with Bilateral Mesial Temporal Lobe Epilepsy.

The Risk-Benefit Ratio for Temporal Lobe Resection in Patients with Bilateral Mesial Temporal Lobe Epilepsy.

18FDG‐PET in different subtypes of temporal lobe epilepsy: SEEG validation and predictive value

The objective of the study was to characterize interictal 18-fluorodeoxyglucose-positron emission tomography ((18) FDG-PET) whole-brain voxel-based metabolic patterns among distinct subtypes of temporal lobe epilepsy (TLE), as defined by stereo-electroencephalography (SEEG) and to determine predictive value of PET result on postoperative outcome. Fifty-four consecutive patients with pharmacoresistant TLE were enrolled retrospectively after a comprehensive presurgical evaluation. This evaluation defined: 7 lateral TLE, 17 mesial TLE, 14 "plus" TLE, and 16 bilateral TLE. Whole-brain voxel-based brain metabolism was studied in each group of patients, in comparison to 23 healthy subjects, and individual classification was evaluated by cross-validation using the found clusters. An (18) FDG-PET index was moreover calculated for each patient, based on the individual Z-score of the most significant cluster extracted on the comparison between patients' subgroup and healthy subjects. Logistic regression analysis was used to estimate factors associated with postoperative outcome (Engel's classes III-IV vs. I-II), including age, gender, disease duration, seizure frequency, as well as magnetic resonance imaging (MRI) and PET findings. Different patterns of hypometabolism were found inside and outside the epileptogenic zone, among patients with distinct subgroups of TLE, in comparison to healthy subjects (p < 0.001, corrected for the cluster). At individual level, cross-validation showed satisfactory discrimination between the four groups with 71.4-88.2% overall accuracy. Multivariate analysis shows that (18) FDG-PET index was the only significant predictor of postoperative outcome to distinguish between Engel's classes I-II and III-IV (p = 0.037). Overall, this whole-brain voxel-based analysis validates specific patterns of hypometabolism, inside and outside the EZ, in distinct subgroups of patients with TLE, as defined by SEEG gold standard, and in relation with postoperative outcome.

Temporal lobe epilepsy and emotion recognition without amygdala: a case study of Urbach‐Wiethe disease and review of the literature

We describe the epilepsy features and emotion recognition abilities (recognition of basic facial emotions and recognition of emotional prosody) in a patient with Urbach-Wiethe disease with bilateral amygdala calcifications. Our data, supported by ictal video-EEG recording, indicated that our patient suffered from mesial temporal lobe epilepsy. Emotion recognition abilities were compared to those of healthy controls and those of patients with bilateral mesial temporal lobe epilepsy. Our patient showed a selective impairment of the recognition of facial expression of fear, whereas recognition of emotional prosody was preserved, in contrast to bilateral mesial temporal lobe epilepsy patients that presented with deficits in both domains. We also reviewed the literature on epilepsy in Urbach-Wiethe disease (41 patients). Our findings suggest that in Urbach-Wiethe disease, the circumscribed damage of both amygdalae results in a selective dysfunction of fearful face processing, in contrast to bilateral mesial temporal lobe epilepsy patients who present with a widespread and multimodal impairment in the judgement of emotional stimuli.

Epilepsy surgery in patients with bilateral temporal lobe seizures: a systematic review.

We explored the association between magnetic resonance imaging (MRI) lesion, degree of seizure laterality on intracranial electroencephalography (iEEG), and seizure outcome in patients with ambiguous or presumed bilateral temporal lobe epilepsy (BiTLE) on scalp EEG. We systematically reviewed the literature using Embase and MEDLINE up to May 31, 2012. Patients with bilateral iEEG, temporal lobe surgery, and follow-up ≥1 year were included. We undertook three separate analyses on patients whose scalp EEG showed ambiguous onset or BiTLE (1) group data of those whose iEEG demonstrated unilateral TLE, (2) group data of those whose iEEG demonstrated BiTLE, (3) individual patient analysis in those with BiTLE for whom iEEG seizure laterality data were provided. Of 1,403 patients with ambiguous or presumed BiTLE on scalp EEG, 1,027 (73%) proved to have unilateral TLE on iEEG and contributed to the first analysis. Of these, 58% had Engel class I and 9% Engel class II outcomes. Of 132 patients in the second analysis (true BiTLE), Engel class I and II outcomes were achieved in 23% and 14%, respectively. Of 41 patients in the third analysis, 66% and 2% had Engel class I and II outcomes, respectively. The median proportion of seizures ipsilateral to the resection on iEEG did not differ between BiTLE patients with Engel class I-II (76%) and Engel III-IV (78%) outcomes (p = 0.87). Patients with ambiguous or independent bitemporal seizure onset on scalp EEG achieved good surgical outcomes. Overall, a significantly higher proportion of patients achieved good outcomes when iEEG showed unilateral TLE (67%) than when it showed true BiTLE (45%). However, the degree of seizure lateralization in those with BiTLE was not associated with seizure outcome, and it has a limited role in selecting the side of surgery.