Lateralization Of Epilepsy Research Articles

Global temporal lobe asymmetry as a semi-quantitative imaging biomarker for temporal lobe epilepsy lateralization: A machine learning classification study.

The purpose of this study was to evaluate the utility of global semi-quantitative analysis via fluorine-18-flurodeoxyglucose positron emission tomography (18F-FDG PET) at lateralizing seizure foci and diagnosing patients with unilateral temporal lobe epilepsy (TLE). Seventeen patients with unilateral TLE (11 right TLE and 6 left TLE) were retrospectively selected for semi-quantitative 18F-FDG PET analysis. Twenty-three control subjects with a Mini Mental State Examination (MMSE) score of 29 or greater were selected for comparison. Globally averaged standardized uptake value (gSUVmean) was computed for each temporal lobe. Lateralization indices (LI) and the absolute value of lateralization indices (|LI|) were calculated to assess the degree of asymmetry in each subject. Logistic regression analyses were performed at a probability cutoff of 0.5 to classify TLE patients as left or right TLE and to discriminate patients from control subjects. Receiver operating characteristic (ROC) curves were generated to evaluate the utility of LI and |LI| as classification predictors. The Bland Altman test was used to evaluate the reproducibility of the measurements. There was a statistically significant difference in gSUVmean computed LI between left and right TLE patients (P<0.01). There was no statistically significant difference in |LI| between the patient and control groups (P=0.22). Logistic regression revealed that 82% of TLE patients were lateralized correctly using LI as the sole predictor. The area under the ROC curve (AUC) was 0.80. Logistic regression using |LI| on the combined patient/control population showed a diagnostic accuracy of 65% and an AUC of 0.44. Bland Altman analysis revealed an intra-observer reproducibility of 96% and an inter-observer reproducibility of 96% and 91% on successive trials. We conclude that gSUVmean computed LI is a reliable and reproducible measure for predicting seizure lateralization in unilateral TLE patients. However, gSUVmean computed |LI| does not appear to be particularly effective at diagnosing TLE patients from control subjects. Further studies with more patients should investigate other machine learning techniques that combine gSUVmean with other diagnostic predictors.

Dysfunctional Brain Networking among Autonomic Regulatory Structures in Temporal Lobe Epilepsy Patients at High Risk of Sudden Unexpected Death in Epilepsy.

Sudden unexpected death in epilepsy (SUDEP) is common among young people with epilepsy. Individuals who are at high risk of SUDEP exhibit regional brain structural and functional connectivity (FC) alterations compared with low-risk patients. However, less is known about network-based FC differences among critical cortical and subcortical autonomic regulatory brain structures in temporal lobe epilepsy (TLE) patients at high risk of SUDEP. 32 TLE patients were risk-stratified according to the following clinical criteria: age of epilepsy onset, duration of epilepsy, frequency of generalized tonic-clonic seizures, and presence of nocturnal seizures, resulting in 14 high-risk and 18 low-risk cases. Resting-state functional magnetic resonance imaging (rs-fMRI) signal time courses were extracted from 11 bilateral cortical and subcortical brain regions involved in autonomic and other regulatory processes. After computing all pairwise correlations, FC matrices were analyzed using the network-based statistic. FC strength among the 11 brain regions was compared between the high- and low-risk patients. Increases and decreases in FC were sought, using high-risk > low-risk and low-risk > high-risk contrasts (with covariates age, gender, lateralization of epilepsy, and presence of hippocampal sclerosis). High-risk TLE patients showed a subnetwork with significantly reduced FC (t = 2.5, p = 0.029) involving the thalamus, brain stem, anterior cingulate, putamen and amygdala, and a second subnetwork with significantly elevated FC (t = 2.1, p = 0.031), which extended to medial/orbital frontal cortex, insula, hippocampus, amygdala, subcallosal cortex, brain stem, thalamus, caudate, and putamen. TLE patients at high risk of SUDEP showed widespread FC differences between key autonomic regulatory brain regions compared to those at low risk. The altered FC revealed here may help to shed light on the functional correlates of autonomic disturbances in epilepsy and mechanisms involved in SUDEP. Furthermore, these findings represent possible objective biomarkers which could help to identify high-risk patients and enhance SUDEP risk stratification via the use of non-invasive neuroimaging, which would require validation in larger cohorts, with extension to patients with other epilepsies and subjects who succumb to SUDEP.

Classification of ictal and seizure-free HRV signals with focus on lateralization of epilepsy.

Epileptic onsets often affect the autonomic function of the body during a seizure, whether it is in ictal, interictal or post-ictal periods. The different effects of localization and lateralization of seizures on heart rate variability (HRV) emphasize the importance of autonomic function changes in epileptic patients. On the other hand, the detection of seizures is of primary interests in evaluating the epileptic patients. In the current paper, we analyzed the HRV signal to develop a reliable offline seizure-detection algorithm to focus on the effects of lateralization on HRV. We assessed the HRV during 5-min segments of continuous electrocardiogram (ECG) recording with a total number of 170 seizures occurred in 16 patients, composed of 86 left-sided and 84 right-sided focus seizures. Relatively high and low-frequency components of the HRV were computed using spectral analysis. Poincaré parameters of each heart rate time series considered as non-linear features. We fed these features to the Support Vector Machines (SVMs) to find a robust classification method to classify epileptic and non-epileptic signals. Leave One Out Cross-Validation (LOOCV) approach was used to demonstrate the consistency of the classification results. Our obtained classification accuracy confirms that the proposed scheme has a potential in classifying HRV signals to epileptic and non-epileptic classes. The accuracy rates for right-sided and left-sided focus seizures were obtained as 86.74% and 79.41%, respectively. The main finding of our study is that the patients with right-sided focus epilepsy showed more reduction in parasympathetic activity and more increase in sympathetic activity. It can be a marker of impaired vagal activity associated with increased cardiovascular risk and arrhythmias. Our results suggest that lateralization of the seizure onset zone could exert different influences on heart rate changes. A right-sided seizure would cause an ictal tachycardia whereas a left-sided seizure would result in an ictal bradycardia.

Intact information sampling in mesial temporal lobe epilepsy.

Previous studies have reported deficits in decision making under ambiguity for patients with mesial temporal lobe epilepsy (mTLE). It is unknown whether mTLE is also associated with alterations at a predecisional stage. This study aimed to gain insight into predecisional processing of patients with mTLE. We compared performance of patients with mTLE (n = 25) with that of healthy controls (n = 75) on the information sampling task (IST), a task assessing reflection-impulsivity and predecisional information sampling. Patients and healthy controls showed a similar performance pattern in both conditions of the IST as indicated by the amount of information gathered, the degree of uncertainty tolerated, and the number of decision errors made. They both also demonstrated a significant sensitivity to the different reward characteristics of the task. For the patient group, we found no significant effects on performance on the IST of epilepsy lateralization, abnormality side, structural abnormality (hippocampus vs. amygdala), and medication (monotherapy vs. polytherapy). Reflection processes and predecisional information sampling as tested by the IST are intact in mTLE. Patients collect as much information as healthy individuals and adapt their behavior according to the changing reward conditions. Our findings indicate that in well-defined risk situations, where memory demands are sufficiently minimized, patients with mTLE should be able to gather sufficient information, weight risks and benefits, and make advantageous decisions.

Biceps electromyography in dialeptic and automotor seizures with and without secondary generalization

ObjectiveLocalization of seizure onset during presurgical video-EEG monitoring is indispensable for successful epilepsy surgery. Sometimes analysis of ictal EEG and video fails to identify this zone. Therefore, this study explored the hypothesis that ictal EMG recordings contribute to the lateralization or localization of focal epilepsy. MethodsAll patients with automotor or dialeptic seizures with or without secondary generalization were prospectively included during presurgical video-EEG monitoring over a 5years study period. We analyzed characteristics of ictal biceps EMG and compared the results to EEG and video findings. Results79 patients with 185 seizures were included (51.9% male; 73.5% automotor and 26.5% dialeptic seizures; 24.3% seizures secondarily generalized). Even in dialeptic seizures, muscle tone increased bilaterally within seconds after EEG seizure onset (66.7%) without clinical movements. Bilateral “spindle-shaped” EMG activity during the automotor phase predicted secondary generalization in 88.7%. Increase of muscle activity in the contralateral side of the body in the beginning of the secondarily generalized tonic–clonic phase was detected in 78.1% after automotor seizures whereas this phenomenon was less pronounced after dialeptic seizures (69.2%). 38.5% of dialeptic seizures evolved into generalized tonic–unilateral clonic seizures. ConclusionIctal EMG recordings provide lateralizing signs especially in secondarily generalized automotor seizures. In addition, the study suggested that secondary generalization in automotor seizures is determined early already during the automotor phase. Dialeptic seizures can evolve only unilaterally into a tonic–clonic seizure while the other side of the body remains tonic. SignificanceIctal biceps EMG can provide further information regarding lateralization of epileptic seizures.

Support Vector Machine with nonlinear-kernel optimization for lateralization of epileptogenic hippocampus in MR images.

Surgical treatment is suggested for seizure control in medically intractable epilepsy patients. Detailed pre-surgical evaluation and lateralization using Magnetic Resonance Images (MRI) is expected to result in a successful surgical outcome. In this study, an optimized pattern recognition approach is proposed for lateralization of mesial Temporal Lobe Epilepsy (mTLE) patients using asymmetry of imaging indices of hippocampus. T1-weighted and Fluid-Attenuated Inversion Recovery (FLAIR) images of 76 symptomatic mTLE patients are considered. First, hippocampus is segmented using automatic and manual segmentation methods; then, volumetric and intensity features are extracted from the MR images. A nonlinear Support Vector Machine (SVM) with optimized Gaussian Radial Basis Function (GRBF) kernel is used to classify the imaging features. Using leave-one-out cross validation, this method results in a correct lateralization rate of 82%, a probability of detection for the left side of 0.90 (with false alarm probability of 0.04) and a probability of detection for the right side of 0.69 (with zero false alarm probability). The lateralization results are compared to linear SVM, multi-layer perceptron Artificial Neural Network (ANN), and volumetry and FLAIR asymmetry analysis. This lateralization method is suggested for pre-surgical evaluation using MRI before surgical treatment in mTLE patients. It achieves a more correct lateralization rate and fewer false positives.

Time-shift homotopic connectivity in mesial temporal lobe epilepsy.

Voxel-mirrored intrinsic functional connectivity allows the depiction of interhemispheric homotopic connections in the human brain, whereas time-shift intrinsic functional connectivity allows the detection of the extent of brain injury by measuring hemodynamic properties. We combined time-shift voxel-mirrored homotopic connectivity analyses to investigate the alterations in homotopic connectivity in mesial temporal lobe epilepsy and assessed the value of applying this approach to epilepsy lateralization and the prediction of surgical outcomes in mesial temporal lobe epilepsy. Resting-state functional MR imaging data were acquired from patients with unilateral mesial temporal lobe epilepsy (n=62) (31 left- and 31 right-side) and healthy controls (n=33). Dynamic interhemispheric homotopic architecture seeding from each hemisphere was individually calculated by 0, 1, 2, and 3 repetition time time-shift voxel-mirrored homotopic connectivity. Voxel-mirrored homotopic connectivity maps were compared between the patient and control groups by using 1-way ANOVA for each time-shift condition, separately. Group comparisons were further performed on the laterality of voxel-mirrored homotopic connectivity in each time-shift condition. Finally, we correlated the interhemispheric homotopic connection to the surgical outcomes in a portion of the patients (n=20). The patients with mesial temporal lobe epilepsy showed decreased homotopic connectivity in the mesial temporal structures, temporal pole, and striatum. Alterations of the bihemispheric homotopic connectivity were lateralized along with delays in the time-shift in mesial temporal lobe epilepsy. The patients with unsuccessful surgical outcomes presented larger interhemispheric voxel-mirrored homotopic connectivity differences. This study showed whole patterns of dynamic alterations of interhemispheric homotopic connectivity in mesial temporal lobe epilepsy, extending the knowledge of abnormalities in interhemispheric connectivity in this condition. Time-shift voxel-mirrored homotopic connectivity has the potential for lateralization of unilateral mesial temporal lobe epilepsy and may have the capability of predicting surgical outcomes in this condition.

The overall pathological status of the left hippocampus determines preoperative verbal memory performance in left mesial temporal lobe epilepsy

Studies on hippocampal cell loss in epilepsy have produced diverging evidence as to which subfields are specifically related to memory. This may be due to rather small and often heterogeneous samples, or to different memory measures. Therefore, the current study examined hippocampal cell densities and memory in a large sample of patients with solely mesial temporal lobe epilepsy (mTLE), employing measures with proven sensitivity to mesiotemporal pathology. In 104 patients who had undergone epilepsy surgery for mTLE, we evaluated the role of segmental hippocampal cell loss and its underlying factor structure with regard to presurgical verbal and figural memory while controlling for side-of-surgery and hemispheric dominance. First of all, patients showed material-specific memory impairment concordant with the lateralization of epilepsy. Factor analysis of segmental cell loss revealed a single factor reflecting the overall integrity of the hippocampus. The overall pathological status of the left hippocampus correlated with verbal memory parameters (r = 0.33-0.34, P < 0.05), especially when controlling for atypical hemispheric dominance (r = 0.50-0.57, P < 0.01), and explained up to 33% of the observed variance. Further analyses revealed no superior role of a single subfield or cell loss pattern for memory performance. No systematic relations between neuronal cell densities of the right hippocampus and memory function were found, nor did left or right hippocampal pathology explain figural memory parameters. The results suggest that the overall pathological status of the left hippocampus - rather than a specific subfield pathology - is predictive for verbal memory in mTLE. The finding that figural memory parameters, although sensitive to right mTLE, were not related to neuronal cell densities of the right hippocampus, puts the left/right hippocampus verbal/nonverbal memory dichotomy into perspective.

Risk factors for spatial memory impairment in patients with temporal lobe epilepsy

At present, the risk factors for world-centered (allocentric) navigation impairment in patients with temporal lobe epilepsy (TLE) are not known. There is some evidence on the importance of the right hippocampus but other clinical features have not been investigated yet. In this study, we used an experimental human equivalent to the Morris water maze to examine spatial navigation performance in patients with drug-refractory unilateral TLE. We included 47 left-hemisphere speech dominant patients (25 right sided; 22 left sided). The aim of our study was to identify clinical and demographic characteristics of TLE patients who performed poorly in allocentric spatial memory tests.Our results demonstrate that poor spatial navigation is significantly associated with younger age at epilepsy onset, longer disease duration, and lower intelligence level. Allocentric navigation in TLE patients was impaired irrespective of epilepsy lateralization. Good and poor navigators did not differ in their age, gender, or preoperative/postoperative status.This study provides evidence on risk factors that increase the likelihood of allocentric navigation impairment in TLE patients. The results indicate that not only temporal lobe dysfunction itself but also low general cognitive abilities may contribute to the navigation impairment.

Ictal spitting in left temporal lobe epilepsy and fMRI speech lateralization

Ictal spitting is a “rare” peri-ictal vegetative sign (PIVS) observed n temporal lobe epilepsy (TLE). Some articles analyzing its lateralzing value have demonstrated that ictal spitting indicates a seizure nset in the non-dominant speech hemisphere [1]. Other studies nd case reports have not shown a lateralizing value for ictal spiting, probably because of low incidence and small sample size [2]. n a recent paper, ictal spitting occurred in 1.03% of patients with LE and 0.26% of seizures arising from the non-dominant temporal obe [3]. We report a man with pharmacoresistent epilepsy who ad a dysembryoplastic neuroepithelial tumor (DNET) in the left emporal lobe and who was considered as a surgical candidate. e recorded his typical seizures. His seizures were accompaied by ictal spitting that might suggest seizure origin from the on-dominant temporal lobe, but the fMRI language lateralization evealed speech activation on the left side.

Déjà-vu in temporal lobe epilepsy: Metabolic pattern of cortical involvement in patients with normal brain MRI

To contribute to the identification of brain regions involved in déjà-vu, we studied the metabolic pattern of cortical involvement in patients with seizures of temporal lobe origin presenting with or without déjà-vu. Using voxel-based analysis of 18FDG-PET brain scans, we compared glucose metabolic rate of 8 patients with déjà-vu, 8 patients without déjà-vu, and 20 age-matched healthy subjects. Patients were selected after comprehensive non-invasive presurgical evaluation, including normal brain MRI and surface electroclinical features compatible with unilateral temporal lobe epilepsy (TLE). Patients with and without déjà-vu did not differ in terms of age, gender, epilepsy lateralization, epilepsy onset, epilepsy duration, and other subjective ictal manifestations. TLE patients with déjà-vu exhibited ipsilateral hypometabolism of superior temporal gyrus and of parahippocampal region, in the vicinity of perirhinal/entorhinal cortex, in comparison either to healthy subjects or to TLE patients without déjà-vu ( p < 0.05 FDR-corrected). By contrast, no difference was found between patient subgroups for hypometabolism of hippocampus and amygdala. At an individual-level, in comparison to healthy subjects, hypometabolism of both parahippocampal region and superior temporal gyrus was present in 7/8 patients with déjà-vu. Hippocampal metabolism was spared in 3 of these 7 patients. These findings argue for metabolic dysfunction of a medial–lateral temporal network in patients with déjà-vu and normal brain MRI. Within the medial temporal lobe, specific involvement of the parahippocampal region, often in the absence of hippocampal impairment, suggests that the feeling of familiarity during seizures greatly depends on alteration of the recognition memory system.

Visual naming performance after ATL resection: Impact of atypical language dominance

Purpose To characterize the interaction between language dominance and lateralization of the epileptic focus for pre- and postoperative Boston Naming Test (BNT) performance in patients undergoing anterior temporal lobectomy (ATL). Methods Analysis of pre- and postoperative BNT scores depending on lateralization of language as measured by the intracarotid amobarbital procedure (IAP) versus lateralization of the temporal lobe epileptic focus. Results Changes between pre- and postoperative BNT performance depended on epilepsy lateralization (effect size = 0.189) with significant decrease in patients undergoing left ATL. Subgroup analysis in these showed that postoperative decline in BNT scores was significant in patients with atypical ( n = 14; p < 0.05), but did not reach statistical significance in patients with left language dominance ( n = 36; p = 0.09). Chi-square test revealed a trend of higher proportions of patients experiencing significant postsurgical deterioration in naming performance in atypical (57.1%) as compared to left language dominance (30.6%; p = 0.082). Surgical failure was also associated with greater decline of BNT scores and was more common in atypical than in left language dominant patients ( χ 2 (1, n = 98) = 4.62, p = 0.032). Age of onset, duration of epilepsy, and seizure frequency had no impact on changes in BNT performance. Conclusion Atypical language dominance is a predictor of change in visual naming performance after left ATL and may also impact postsurgical seizure control. This should be considered when counseling surgical candidates.

Neuropsychologie bei Epilepsie

In order to understand cognitive impairment associated with epilepsy, it is essential to appreciate that independent static and dynamic factors affect brain function in this disease. Whereas morphological lesions or structural changes are associated with more or less irreversible deficits, epileptic activity, seizures, and the treatment of epilepsy can cause dynamic and principally reversible impairment. The relative contribution of these factors differs depending on the type of epilepsy, the age at lesion/epilepsy onset, the localization and lateralization of epilepsy and individual demographic patient characteristics. Altered brain structure and function can result in epilepsy, but epilepsy can also alter the functional cerebral organization of the brain. Thus epilepsy-related cognitive impairment must be integrated within a developmental neuropsychological framework. The aetiology of epilepsy is strongly related to the age of onset. From a neuropsychological point of view, it makes a big difference for cognitive outcome as to whether epilepsy hits the maturing versus mature or aging brain. Dependent on this, epilepsy can result in retardation, loss of acquired functions, or accelerated mental decline. It will be demonstrated that cognitive impairments in epilepsy mostly exist from the beginning of epilepsy, that early onset lesions/epilepsy interfere with mental development, and that a progressive aetiology, severe seizures, and lesions secondary to epilepsy may accelerate mental decline. It will furthermore be discussed that uncontrolled epilepsy and epileptic activity may reversibly and irreversibly contribute to cognitive impairment. The same is demonstrated with regard to the pharmacological treatment of epilepsy. Finally, the cognitive risks and benefits of epilepsy surgery and the advantages of selective surgery will be addressed. The consequences for the neuropsychological assessment are discussed in part two of this review.

Use of Short Echo Time Two-Dimensional 1H-Magnetic Resonance Spectroscopy in Temporal Lobe Epilepsy with Negative Magnetic Resonance Imaging Findings

We evaluated short echo time two-dimensional 1H magnetic resonance spectroscopy (2D-1HMRS) with the point-resolved spatial selection (PRESS) protocol in temporal lobe epilepsy (TLE) patients with negative magnetic resonance imaging (MRI) findings and described the characteristics of 2D-(1)HMRS in the epileptic focus. Thirty-eight TLE patients with negative conventional MRI findings and 10 healthy controls were studied by 2D-1HMRS. A 128-channel prolonged video-electroencephalographic (EEG) method was used as the standard for epileptogenic focus localization to evaluate N-acetyl aspartate/(choline + creatine + phosphocreatine) (NAA/[Cho + Cr-PCr]), glutamate + glutamine/creatine (Glx/Cr-PCr) and myo-inositol/Cr-PCr ratios in patients with negative MRI findings. The 2D-1HMRS showed that 32/38 patients and all healthy controls had stable baselines and good signal-to-noise ratios. Compared with the healthy controls, 32 patients showed abnormal NAA/(Cho + Cr-PCr) ratios in the hippocampus and, in 25 of these patients, focus lateralization agreed with the EEG. It is concluded that short echo time 2D-1HMRS with the PRESS protocol can help find abnormalities in lateralization of temporal epilepsy in patients with negative MRI findings.

Is Behavior in Temporal Lobe Epilepsy Different than in Other Epilepsies? the Jury is Out

Interictal Depression, Anxiety, Personality Traits, and Psychological Dissociation in Patients with Temporal Lobe Epilepsy (TLE) and Extra-TLE. Swinkels WA, van Emde Boas W, Kuyk J, van Dyck R, Spinhoven P. Epilepsia 2006;47(12):2092–2103. PURPOSE: This study was performed to investigate the relation between symptoms of interictal depression, anxiety, personality traits, and psychological dissociation with the localization and lateralization of the epileptogenic zone in patients with partial epilepsy. METHODS: All patients were diagnosed according to the localization-related concept of the 1989 International League Against Epilepsy (ILAE) Classification of Epilepsies and Epileptic Syndromes, and the localization and lateralization of the epileptogenic zone was established by using the clinical criteria for noninvasive presurgical evaluation. This resulted in 67 patients with temporal lobe epilepsy (TLE) and 64 patients with extra-TLE. All patients were assessed on the various aspects of psychopathology by using a comprehensive battery of standardized diagnostic instruments. RESULTS: We did not find the hypothesized excess of psychiatric symptoms in patients with (mesial) TLE in comparison with patients with extra-TLE. We also found no differences between patients with the lateralization of epilepsy in the left versus the right hemisphere. CONCLUSIONS: TLE per se cannot be considered a risk factor in developing more or more severe symptoms of psychopathology in patients with partial epilepsy. Concomitant factors, such as the duration of epilepsy, seizure frequency, and frontal lobe dysfunction may play an additional role. Our findings support the hypothesis of a multifactorial explanation for the psychiatric symptoms in patients with epilepsy.

Interictal Depression, Anxiety, Personality Traits, and Psychological Dissociation in Patients with Temporal Lobe Epilepsy (TLE) and Extra‐TLE

This study was performed to investigate the relation between symptoms of interictal depression, anxiety, personality traits, and psychological dissociation with the localization and lateralization of the epileptogenic zone in patients with partial epilepsy. All patients were diagnosed according to the localization-related concept of the 1989 International League Against Epilepsy (ILAE) Classification of Epilepsies and Epileptic Syndromes, and the localization and lateralization of the epileptogenic zone was established by using the clinical criteria for noninvasive presurgical evaluation. This resulted in 67 patients with temporal lobe epilepsy (TLE) and 64 patients with extra-TLE. All patients were assessed on the various aspects of psychopathology by using a comprehensive battery of standardized diagnostic instruments. We did not find the hypothesized excess of psychiatric symptoms in patients with (mesial) TLE in comparison with patients with extra-TLE. We also found no differences between patients with the lateralization of epilepsy in the left versus the right hemisphere. TLE per se cannot be considered a risk factor in developing more or more severe symptoms of psychopathology in patients with partial epilepsy. Concomitant factors, such as the duration of epilepsy, seizure frequency, and frontal lobe dysfunction may play an additional role. Our findings support the hypothesis of a multifactorial explanation for the psychiatric symptoms in patients with epilepsy.

False Lateralization of Mesial Temporal Lobe Epilepsy by Noninvasive Neurophysiological Examinations-Case Report-

Mesial temporal lobe epilepsy (mTLE) is the most common form of symptomatic localization-related epilepsy and is surgically remediable. Lateralization of the seizure onset is particularly important to determine from a surgical perspective. A 39-year-old woman with intractable mTLE first exhibited seizure at the age of 3 years. She experienced epigastric sensation and placed her right hand on her abdomen before falling backward. Although interictal scalp electroencephalography (EEG), sphenoidal scalp ictal EEG, and magnetoencephalography showed right temporal side focus, computed tomography and magnetic resonance imaging showed atrophy of the left cerebral hemisphere. Single photon emission computed tomography with technetium-99m ethyl cysteinate dimmer and I-123 iomazenil showed obscure focus on the left side. As a discrepancy existed between the results of neurophysiological examinations and imaging, we performed subdural electrode implantation on the bilateral temporal lobe. Although a bemegride-induced seizure arose from the right side during the subdural recording, the onset of 5 habitual seizures was observed in the left hippocampus. On the basis of these results, the seizure was diagnosed as left mTLE, and left anterior temporal lobectomy and amygdalohippocampectomy were performed. The patient has been free from the seizures for more than 1.5 years of follow up. Bilateral subdural electrode measurement of habitual seizures is indispensable for clarifying the actual focus when a discrepancy exists between neuroimaging and noninvasive neurophysiological examinations.

Lateralization of human temporal lobe epilepsy by 31P NMR spectroscopic imaging at 4.1 T.

To compare the phosphorous metabolite ratios in the mesial temporal lobe of healthy volunteers (n = 20) with the corresponding ratios in patients with temporal lobe epilepsy (n = 30) using 31P NMR spectroscopic imaging and to lateralize the seizure focus in temporal lobe epilepsy patients using various phosphorous metabolite ratios-phosphocreatine to inorganic phosphate (PCr/Pi), PCr to adenosine triphosphate (PCr/gamma-ATP), and (gamma-ATP/Pi)--and to compare with clinical lateralization results. All 31P NMR spectroscopic imaging studies were performed on a high-field, 4.1 T, whole-body NMR spectroscopic imaging system using a 31P/1H double-tuned volume coil. We found an average reduction of 15% in the PCr/Pi and gamma-ATP/Pi ratios compared with the corresponding ratios in healthy volunteers in the entire mesial temporal lobe, and more than a 30% reduction in these two ratios in the anterior region of the epileptogenic mesial temporal lobe. These ratios were also reduced significantly in the ipsilateral lobe when compared with their corresponding values in the contralateral lobe. In patients we lateralized the seizure focus, based on these 31P NMR data, and compared the results with the clinical lateralization. The lateralization based on either the PCr/Pi or the gamma-ATP/Pi ratio yielded a correspondence of 70 to 73% with the final clinical lateralization. In the subgroup of patients (n = 9) that needed intracranial EEG for the presurgical lateralization because of inconclusive results from the noninvasive methods, a 78% correspondence was found with the 31P NMR-based lateralization, whereas MRI provided a correspondence of only 33%, and scalp EEG provided a correspondence of only 56%. These results suggest the utility of adding the 31P NMR method to the group of noninvasive modalities used for presurgical decision making in temporal lobe epilepsy patients.

Hemispheric lateralization of motor and speech functions after early brain lesion: Study of 73 epileptic patients with intracarotid amytal test

This study reports results of a bilateral intracarotid amytal test in 73 epileptic patients with medically intractable focal seizures. No right-handers but 50% of left-handers have a right dominance for speech in this particular population. Lateralization of cerebral speech functions, as well as manual preference, are dependent on the neurological disease and can shift conjointly or independently. We study the relationships of those shifts to different variables related to the cerebral pathology: age at onset and lateralization of epilepsy, extensive brain damage, neurological deficit.