The value of intraoperative electrocorticography in surgical decision making for temporal lobe epilepsy with normal MRI

Purpose: We hypothesized that acute intraoperative electrocorticography (ECoG) might identify a subset of patients with magnetic resonance imaging (MRI)–negative temporal lobe epilepsy (TLE) who could proceed directly to standard anteromesial resection (SAMR), obviating the need for chronic electrode implantation to guide resection. Methods: Patients with TLE and a normal MRI who underwent acute ECoG prior to chronic electrode recording of ictal onsets were evaluated. Intraoperative interictal spikes were classified as mesial (M), lateral (L), or mesial/lateral (ML). Results of the acute ECoG were correlated with the ictal‐onset zone following chronic ECoG. Onsets were also classified as “M,”“L,” or “ML.” Positron emission tomography (PET), scalp‐EEG (electroencephalography), and Wada were evaluated as adjuncts. Key Findings: Sixteen patients fit criteria for inclusion. Outcomes were Engel class I in nine patients, Engel II in two, Engel III in four, and Engel IV in one. Mean postoperative follow‐up was 45.2 months. Scalp EEG and PET correlated with ictal onsets in 69% and 64% of patients, respectively. Wada correlated with onsets in 47% of patients. Acute intraoperative ECoG correlated with seizure onsets on chronic ECoG in all 16 patients. All eight patients with “M” pattern ECoG underwent SAMR, and six (75%) experienced Engel class I outcomes. Three of eight patients with “L” or “ML” onsets (38%) had Engel class I outcomes. Significance: Intraoperative ECoG may be useful in identifying a subset of patients with MRI‐negative TLE who will benefit from SAMR without chronic implantation of electrodes. These patients have uniquely mesial interictal spikes and can go on to have improved postoperative seizure‐free outcomes.     

Lateralizing value of behavioral arrest in patients with temporal lobe epilepsy

Analysis of ictal semiology is essential to presurgical evaluation of patients with epilepsy. To assess the localizing value of behavioral arrest in temporal lobe epilepsy (TLE), we analyzed 107 video/EEG monitoring-documented seizures of 107 adult patients with TLE for a set of defined seizure phenomena with respect to frequency and sequence of occurrence in relation to epileptogenic (mesial vs extramesial, left vs right) origin. Behavioral arrest was observed more frequently in left-sided temporal seizures: 25.7% of left-sided mesial seizures and 25.0% of left-sided extramesial seizures exhibited behavioral arrest, whereas only 3.4% of right-sided mesial seizures and 10.5% of right-sided extramesial seizures were associated with behavioral arrest. In addition, occurence of behavioral arrest within the sequence of seizure phenomena was remarkably consistent, being observed mainly as the first apparent feature of seizure onset. Thus, behavioral arrest is a valuable early indicator of a left-sided temporal epileptogenic focus in adult patients with TLE.     

Postoperative changes in cerebral metabolism in temporal lobe epilepsy

BACKGROUND: Fludeoxyglucose F 18 positron emission tomography ((18)F-FDG-PET) can detect focal metabolic abnormalities ipsilateral to the seizure focus in 80% of patients with temporal lobe epilepsy (TLE). Regions outside the epileptogenic zone can also be affected. We hypothesized that these remote regions might show altered metabolism, tending to return toward normal values, after surgery. DESIGN: Interictal preoperative and postoperative (18)F-FDG-PET metabolism were compared in patients with refractory TLE. Based on pathological findings, disease was classified in the following 3 groups: mesial temporal sclerosis, mass lesions, and no pathological diagnosis. Quantitative PET data analysis was performed using the region-of-interest template previously described. Global normalization was used to adjust for the effect of antiepileptic medication changes. Data were analyzed by Wilcoxon signed rank test and analysis of variance. SETTING: The Clinical Epilepsy Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health. PATIENTS: Twenty-two patients with refractory TLE. RESULTS: Preoperatively, in all groups, cerebral metabolic rate for glucose was decreased ipsilateral to the resection site in inferior lateral temporal, inferior mesial temporal, and inferior frontal areas and thalamus. Postoperatively, in all groups, cerebral metabolic rate for glucose increased in ipsilateral inferior frontal area and thalamus. In the mesial temporal sclerosis group, we found a statistically significant increase in the contralateral thalamus. CONCLUSION: Temporal lobe epilepsy is associated with extensive preoperative decreased metabolism in inferior lateral temporal, inferior mesial temporal, and inferior frontal areas and thalamus. Postoperatively, we found increased IF and thalamic metabolism. Seizures may have a reversible effect on brain areas connected with, but remote from, the epileptogenic cortex. Arch Neurol. 2000;57:1447-1452     

Volumetric evidence of bilateral damage in unilateral mesial temporal lobe epilepsy

PURPOSE: We sought to analyze the contralateral volumes of the temporal pole, posterior segment of the temporal lobe, amygdala, hippocampus, and parahippocampal gyrus in patients with temporal lobe epilepsy (TLE) due to histologically proven mesial temporal lobe sclerosis (MTLS), seizure free for >or=4 years of postsurgical follow-up. METHODS: Forty-six (23 male) TLE patients, operated on between 1996 and 2001, with histopathologic diagnosis of MTLS, and a postsurgical follow-up of >or=4 years, had their temporal lobe structures manually segmented, measured, and compared with those of 23 normal volunteers, paired as groups for sex, age, and handedness. RESULTS: The mean volumes of the contralateral temporal pole, hippocampus, and parahippocampal gyrus in TLE patients were significantly lower than those in controls. CONCLUSIONS: MRI volumetric data show that the damage in TLE due to MTS may be more widespread and bilateral, even in patients with unilateral TLE by clinical and neurophysiological criteria. Our results are relevant to the discussion of epileptogenic mechanisms in TLE.     

儿童难治性颞叶癫痫的手术治疗

目的 探讨儿童难治性颞叶癫痫术前评估和手术方法 及影响癫痫预后的因素.方法 回顾性分析2007年7月至2009年2月手术治疗的21例儿童难治性癫痫患者中得到随访的19例临床资料,主要为复杂部分性发作.多数患者有腹部不适等发作先兆和咂嘴等发作时伴随自动动作.MRI扫描15例异常.6例行PET扫描均异常.头皮脑电图示局灶痫性放电7例,多灶痫性放电12例.施行一侧颞前叶+海马、杏仁核切除术15例,一侧颞前叶、海马、杏仁核+部分额叶皮层切除术4例.结果 随访12-30个月,癫痫发作结果 ,Engel Ⅰ级13例;Ⅱ级3例;Ⅲ级1例;Ⅳ级2例.随访期间对4例进行神经心理学评估,2例明显好于术前.无永久性神经缺损并发症.术后切除标本病理诊断结果 为颞叶皮层发育不良和颞叶内侧硬化等.结论 颞叶切除治疗儿童难治性癫痫多数预后良好.该手术安全、并发症少.发作表现、EEG以及神经影像学检查对致痫灶定位相互符合时,预示预后良好.早期手术可能对患儿的神经心理学改善有帮助.     

Effects of illness duration on memory processing of patients with temporal lobe epilepsy

PURPOSE: To examine the effects of illness duration on the neural processing of memory in patients with temporal lobe epilepsy (TLE) by using functional MRI. METHODS: Twenty-three TLE patients (16 left, seven right) performed a complex visual scene-encoding task during functional MRI. Region-of-interest (ROI) analyses were used to quantity functional activation in the mesial temporal and frontal lobes. The patients' verbal and visual memory performances were evaluated by standardized neuropsychological tests. Analyses included group comparison and correlations of duration of epilepsy with functional activation and memory performance. RESULTS: Compared with normal controls, TLE patients demonstrated reduced activation bilaterally in the mesial temporal lobe (p=0.003), and the reduction was more pronounced on the ipsilateral side of the seizure focus. Moreover, a longer duration of illness was associated with fewer voxels activated in both the left (p=0.038) and right (p=0.017) mesial temporal lobe. Furthermore, the duration of illness was found to be significantly and negatively correlated with both verbal (p=0.020) and visual (p=0.000) memory functioning. CONCLUSIONS: TLE seems to affect the memory processes in the mesial temporal lobes progressively (i.e., the longer the duration of illness, the lower the brain activation). In turn, the reduction of brain activation negatively affects memory functioning. Finally, the reduction is not limited to the side of seizure but also is observed in the contralateral hemisphere.     

Small temporal pole encephaloceles: A treatable cause of “lesion negative” temporal lobe epilepsy

Epilepsy due to encephaloceles of the temporal pole may be an under recognized, treatable cause of refractory temporal lobe epilepsy (TLE). We describe three adult patients initially labeled “lesion negative” TLE. In all, video–electroencephalography (EEG) revealed ictal theta in the left temporal region and positron emission tomography (PET) showed temporal lobe hypometabolism, but neuropsychology revealed preserved verbal memory. Close inspection of structural magnetic resonance imaging (MRI) suggested subtle abnormalities at the tip of the left temporal lobe. High resolution computed tomography (CT) confirmed bony defects in the inner table of the skull. 3T MRI with fine coronal and sagittal slices indicated cerebrospinal fluid (CSF) and brain tissue protruding into the defects. All proceeded to resection of the temporal tip and became seizure free. Patients with “lesion negative” TLE should have careful review of images covering the temporal pole. If encephalocele is suspected, further imaging with high‐resolution CT and MRI can be helpful. Temporal polar resection, sparing mesial structures, appears to be curative.     

Graph theory findings in the pathophysiology of temporal lobe epilepsy

Temporal lobe epilepsy (TLE) is the most common form of adult epilepsy. Accumulating evidence has shown that TLE is a disorder of abnormal epileptogenic networks, rather than focal sources. Graph theory allows for a network-based representation of TLE brain networks, and has potential to illuminate characteristics of brain topology conducive to TLE pathophysiology, including seizure initiation and spread. We review basic concepts which we believe will prove helpful in interpreting results rapidly emerging from graph theory research in TLE. In addition, we summarize the current state of graph theory findings in TLE as they pertain its pathophysiology. Several common findings have emerged from the many modalities which have been used to study TLE using graph theory, including structural MRI, diffusion tensor imaging, surface EEG, intracranial EEG, magnetoencephalography, functional MRI, cell cultures, simulated models, and mouse models, involving increased regularity of the interictal network configuration, altered local segregation and global integration of the TLE network, and network reorganization of temporal lobe and limbic structures. As different modalities provide different views of the same phenomenon, future studies integrating data from multiple modalities are needed to clarify findings and contribute to the formation of a coherent theory on the pathophysiology of TLE.     

Prognostic factors in anterior temporal lobe resections for mesial temporal lobe epilepsy: multivariate analysis

PURPOSE: Even though there have been several studies on the prognostic factors of temporal lobe epilepsy (TLE) after lobectomy, no studies have been performed for homogeneous mesial TLE. Furthermore, most studies on the predictors of outcome of epileptic surgery were based on univariate analyses and did not consider modern epileptic surgery investigation modalities such as brain magnetic resonance imaging (MRI) and positron emission tomography (PET). We attempted to identify the prognostic factors in anterior temporal lobectomy (ATL) for mesial TLE with multivariate analysis. METHODS: Ninety-three patients with mesial TLE (54 men and 39 women, mean age at surgery, 28.3 +/- 8.2 years) were included in the study. The primary outcome variable was the status of patients in the second postoperative year, classified as either seizure free (except aura), or not seizure free. Clinical, electroencephalographic, MRI, PET, Wada test, and pathological data were considered. RESULTS: Seventy-eight (84.0%) patients had remission of seizures. With univariate analysis, age at surgery (p < 0.001), epilepsy duration before surgery (p = 0.04), and ipsilateral hippocampal sclerosis on MRI (p = 0.02) were found to be significant. By using multivariate analysis, age at surgery (p = 0.001) and ipsilateral hippocampal sclerosis on MRI (p = 0.03) were found to be the most significant prognostic factors. CONCLUSIONS: Age at surgery and hippocampal sclerosis are independent prognostic factors for ATL in mesial TLE. These findings suggest that mesial TLE may be a progressive disorder, and surgical outcome is better when early ATL is performed.     

Clinical correlates of graph theory findings in temporal lobe epilepsy

PurposeTemporal lobe epilepsy (TLE) is considered a brain network disorder, additionally representing the most common form of pharmaco-resistant epilepsy in adults. There is increasing evidence that seizures in TLE arise from abnormal epileptogenic networks, which extend beyond the clinico-radiologically determined epileptogenic zone and may contribute to the failure rate of 30–50% following epilepsy surgery. Graph theory allows for a network-based representation of TLE brain networks using several neuroimaging and electrophysiologic modalities, and has potential to provide clinicians with clinically useful biomarkers for diagnostic and prognostic purposes.MethodsWe performed a review of the current state of graph theory findings in TLE as they pertain to localization of the epileptogenic zone, prediction of pre- and post-surgical seizure frequency and cognitive performance, and monitoring cognitive decline in TLE.ResultsAlthough different neuroimaging and electrophysiologic modalities have yielded occasionally conflicting results, several potential biomarkers have been characterized for identifying the epileptogenic zone, pre-/post-surgical seizure prediction, and assessing cognitive performance. For localization, graph theory measures of centrality have shown the most potential, including betweenness centrality, outdegree, and graph index complexity, whereas for prediction of seizure frequency, measures of synchronizability have shown the most potential. The utility of clustering coefficient and characteristic path length for assessing cognitive performance in TLE is also discussed.ConclusionsFuture studies integrating data from multiple modalities and testing predictive models are needed to clarify findings and develop graph theory for its clinical utility.     

Foramen ovale electrodes in the preoperative evaluation of temporal lobe epilepsy in children

Purpose:  Foramen ovale electrodes (FOEs) can localize the epileptogenic zone in adults with mesial temporal lobe epilepsy (TLE). Our aim was to investigate the feasibility and safety of using FOEs to investigate refractory TLE in children.
Methods:  Thirty-eight children with seizure semiology and video-EEG (electroencephalography) consistent with medically refractory TLE, and/or the presence of a lesion in the temporal lobe, had FOEs inserted. Complications occurring during the monitoring and up to 3 months after surgery and the long-term seizure outcome were registered.
Results:  Forty electrodes were placed in 38 patients. The mean age of the patients was 9.8 years (range 2.3–15.4 years). FOEs confirmed a unilateral mesial temporal lobe seizure onset in 14 patients, onset in both FOEs and lateral electrodes in two patients, and onset in the anterior temporal electrodes in only one patient. Six patients had seizures recorded but were not considered surgical candidates; four patients had no seizures recorded, and 11 patients were further investigated with depth electrodes. One patient (2.6%) developed a hematoma in the cheek, and in two patients the electrodes were extracranial but could still be used for recording. Twenty-eight children had a temporal resection; 25 were Engel class I at follow-up.
Discussion:  FOEs are safe to use in children and provide valuable information on the mesial temporal lobe structures in the preoperative investigation of pediatric TLE. Patient selection for FOE investigation is, however, essential for a conclusive result.     

Ultrasound stimulation inhibits recurrent seizures and improves behavioral outcome in an experimental model of mesial temporal lobe epilepsy

Current therapies for epilepsy consist mostly of pharmacological agents or invasive surgery. Recently, ultrasound (US) stimulation has been considered a promising tool for the noninvasive treatment of brain diseases, including epilepsy. However, in temporal lobe epilepsy (TLE), a common form of epilepsy, neurophysiological and functional outcomes following US stimulation are not well defined. To address this, we developed a paradigm of transcranial pulsed US stimulation to efficiently suppress seizure activity in the initial/acute period in a kainate (KA)-induced mouse model of mesial TLE. Pulsed US stimulation inhibited acute seizure activity and either delayed the onset of or suppressed status epilepticus (SE). Kainate-treated mice that had received US stimulation in the initial period exhibited fewer spontaneous recurrent seizures (SRSs) and improved performance in behavioral tasks assessing sociability and depression in the chronic period of epilepsy. Our results demonstrate that US stimulation in the acute period of epilepsy can inhibit SRSs and improve behavioral outcomes in a mouse model of mesial TLE. The present study suggests that noninvasive transcranial pulsed US stimulation may be feasible as an adjuvant therapy in patients with epilepsy.This article is part of a Special Issue entitled “Status Epilepticus”.     

Correlation of temporal lobe glucose metabolism with the Wada memory test

PURPOSE: The goal of the present study was to examine the relationship of 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) and the Wada memory test in lateralizing memory dominance and epileptic focus. METHODS: FDG-PET and the Wada test were performed in 18 patients with temporal lobe epilepsy (TLE). The asymmetry indices of FDG-PET (PET-AI) were calculated in mesial, polar, anterolateral, midlateral, and posterolateral regions of the temporal lobe, and those of Wada memory test (Wada-AI) were obtained as well. RESULTS: The Wada-AI was significantly correlated with PET-AI in mesial (r = 0.67, p = 0.003), polar (r = 0.55, p = 0.019), anterolateral (r = 0.55, p = 0.019), and midlateral (r = 0.51, p = 0.031) regions of the temporal lobe. However, after a linear regression analysis, PET-AI of only the mesial temporal region was significantly correlated with Wada-AI (p = 0.008). Wada-AI could correctly lateralize the seizure focus in 90% of the left TLE and 75% of the right TLE patients. The PET-AI of the mesial temporal region showed the highest sensitivity of seizure lateralization (80% of left TLE and 87.5% of right TLE). PET-AI of other temporal regions had lower sensitivities (50-80% of left TLE, 20-75% of right TLE). One or two patients showed false seizure lateralization by PET-AI on each temporal region. CONCLUSIONS: Although FDG-PET hypometabolism is observed at both mesial and lateral regions of the temporal lobe in mesial TLE, mesial temporal region appeared to be a dominant and leading area for lateralizing Wada memory dominance and epileptic focus.     

Temporal lobe volumetric cell densities in temporal lobe epilepsy

Volumetric cell densities in 13 different subfields of the temporal lobe were calculated to test various hypotheses about mesial and lateral temporal lobe sclerosis in patients with complex partial epilepsy. In patients benefitting (primary group) from anterior temporal lobectomy (ATL), sclerosis was greater (fewer cells) in anterior than in posterior hippocampus. By contrast, the patients lacking full benefit (nonprimary group) from ATL had decreased numbers of neurons equally distributed from anterior to posterior hippocampus, indicating that zones of mesial temporal cell loss are linked to zones of epileptogenicity. These data support a model of focal hippocampal epilepsy originating from zones of cell loss and synaptic reorganization that is epileptic. There were no differences in cell densities in gyrus hippocampi or in lateral temporal gyri when patients with temporal lobe epilepsy and controls were compared. Hippocampal cell densities in mesial temporal lobe were not reduced in psychomotor epileptic patients with extrahippocampal foci consisting of foreign tissue. Variables in seizure histories were not correlated with Ammon's horn cell densities, indicating that most of the sclerosis preceded the seizures, which did virtually no significant further damage to hippocampus with repeated partial or generalized seizures.     

Surgery for temporal lobe epilepsy after cerebral malaria

The most common indication for epilepsy surgery is temporal lobe epilepsy (TLE) which usually is divided into two categories, mesial and lateral TLE. The commonest pathology underlying mesial temporal lobe epilepsy (MTLE) is mesial temporal sclerosis (MTS); we report on a 50-year-old male patient, who contracted cerebral malaria and developed MTLE shortly thereafter. Magnetic resonance imaging (MRI) showed MTS. Surgical treatment was an anteromedial temporal lobe resection with amygdalohippocampectomy. The patient is seizure free, 36 months after surgical treatment. This is the first report describing MTLE-onset subsequent to cerebral malaria and discussing the potential pathophysiological relationship between cerebral malaria and MTS.     

Emotional facial paresis in temporal lobe epilepsy: its prevalence and lateralizing value.

The selection of patients with medically refractory temporal lobe epilepsy (TLE) for surgery depends on the concordance of data from clinical, imaging and electroencephalographic evaluation. Though clinical examination is often normal, emotional facial paresis has been described in patients with TLE. Utilizing a well-characterized group of mesial TLE (MTLE) patients, who have achieved excellent seizure outcome following anterior temporal lobectomy with amygdalohippocampectomy (ATL), we investigated the prevalence, predictive value and associations of emotional facial paresis. When compared to 8 out of 50 control subjects (16%), 36 out of 50 MTLE patients (72%) exhibited unilateral emotional facial paresis; the difference was highly significant (P<0.0001). The presence of contralateral emotional facial paresis correctly predicted the side of ATL in 86.1% patients. The occurrence of emotional facial paresis was significantly associated with longer duration of epilepsy prior to ATL and left ATL. Our observations confirm that emotional facial parersis contralateral to the side of mesial temporal sclerosis (MTS) is a valuable localizing sign in correctly predicting the epileptogenic temporal lobe. We hypothesize that the presence of an intact right hemisphere and pathological changes more extensive than MTS may be required for emotional facial paresis to readily manifest.     

Analysis of the initial ictal phenomenon in patients with temporal lobe epilepsy

We aimed to assess the localizing value of the initial semiological element in temporal lobe epilepsy (TLE). Video-EEG-documented seizures of 97 adult TLE patients were studied in relation to seizure origin (left versus right; mesial versus extra-mesial). Strikingly, seizures with mesial onset started with very few ictal phenomena, while seizures of extra-mesial origin began with a larger variety of ictal elements. Furthermore, following noticeable distributions were observed for the mesial group: (i) aura was the most common initial ictal phenomenon in the total patient collective, occurring significantly more frequently in mesial than in extra-mesial seizure onset. Aura appeared most often in seizures of left mesial origin. (ii) Vocalization presented a trend towards mesial left seizure origin. (iii) Oral automatisms showed a trend towards mesial seizure origin. Following noticeable distribution was observed for the extra-mesial group: In patients without aura, restlessness as initial ictal phenomenon appeared exclusively in seizures of extra-mesial right origin. Finally, behavioral arrest showed a trend towards left-sided seizure origin. In conclusion, the initial ictal element may add useful information concerning differentiation of seizure onset in TLE.     

Hyperkinetic seizures in patients with temporal lobe epilepsy: clinical features and outcome after temporal lobe resection

Purpose: Temporal lobe epilepsy (TLE) is usually associated with automatisms. Hyperkinetic seizures are supposed to be unusual. Because we witnessed several patients with TLE and ictal hyperkinetic symptoms, we retrospectively assessed the number, clinical findings, and seizure outcome in such patients who had undergone temporal lobe resection. Methods: We reviewed medical history, video–electroencephalography (EEG) recording and neuroimaging of adult patients who underwent epilepsy surgery for TLE at the Kork Epilepsy Center over the last 20 years with a minimum postoperative follow‐up of 12 months. Key Findings: Among 294 patients who were resected exclusively in the temporal region, we identified 17 (6%) who presented with hyperkinetic semiology such as violent vocalization, complex movements of the proximal segments of the limbs, rotation of the trunk, pelvic thrusting, or early tonic or dystonic posturing. Most of the patients had a preceding aura. Ictal EEG activity was located in the corresponding temporal region, usually with a wide distribution over temporal electrodes with fast spread to unilateral frontal electrodes and to the contralateral side. Neuroimaging revealed extended lesions in the temporal lobe involving mesial and neocortical structures. Most of the patients underwent classical anterior temporal lobe resection including amygdalo‐hippocampectomy. Fourteen patients (82%) became completely seizure‐free (Engel class Ia). Histopathology showed mainly focal cortical dysplasia plus hippocampal sclerosis. Significance: Hyperkinetic seizure semiology may occasionally occur in patients with TLE and is, therefore, no contradiction to the hypothesis of TLE if scalp EEG patterns and neuroimaging findings correspond. The postoperative seizure outcome is favorable in such patients and not different from outcome data in classical TLE.     

Semiologic and electrophysiologic correlations in temporal lobe seizure subtypes

PURPOSE: The International League Against Epilepsy (ILAE) classification distinguishes medial and neocortical temporal lobe epilepsies. Among other criteria, this classification relies on the identification of two different electroclinical patterns, those of medial (limbic) and lateral (neocortical) temporal lobe seizures, depending on the structure initially involved in the seizure activity. Recent electrophysiologic studies have now identified seizures in which medial and neocortical structures are both involved at seizure onset. The purpose of the study was therefore to study the correlations of ictal semiology with the spatiotemporal pattern of discharge in temporal lobe seizures. METHODS: The 187 stereoelectroencephalography-recorded seizures from 55 patients were analyzed. Patients were classified into three groups according to electrophysiologic findings: medial (M; seizure onset limited to medial structures, n=24), lateral (L; seizure onset limited to lateral structures, n=13), and medial-lateral (ML; seizure onset involving both medial and lateral structures, n=18). Clinical findings were compared between groups. RESULTS: Initial epigastric sensation, initial fear, delayed oroalimentary and elementary upper limb automatisms, delayed loss of contact, long seizure duration, and absent or rare secondary generalizations were associated with M seizures. Initial auditory illusion or hallucination, initial loss of contact, shorter duration of seizures, and more frequent generalizations were associated with L seizures. Initial epigastric sensation, initial loss of contact, early oroalimentary and verbal automatisms, and long duration of seizures were associated with ML seizures. CONCLUSIONS: Although the syndrome of mesial temporal epilepsy is now relatively well defined, our findings support the idea that the organization of temporal lobe seizures may be complex and that different patterns exist. We demonstrate three distinct patterns, characterized by both semiologic and electrophysiologic features. This distinction may help to define better the epileptogenic zone and the subsequent surgical procedure.     

Neuromagnetic recordings in temporal lobe epilepsy.

The introduction of whole-head magnetoencephalography (MEG) systems facilitating simultaneous recording from the entire brain surface has established MEG as a clinically feasible method for the evaluation of patients with temporal lobe epilepsy (TLE). In mesial TLE, two types of MEG spike dipoles could be identified: an anterior vertical and an anterior horizontal dipole. Dipole orientations can be used to attribute spike activity to temporal lobe subcompartments. Whereas the anterior vertical dipole is compatible with epileptic activity in the mediobasal temporal lobe, the anterior horizontal dipole can be explained by epileptic activity of the temporal tip cortex. In nonlesional TLE, medial and lateral vertical dipoles were found which could distinguish between medial and lateral temporal seizure onset zones as evidenced from invasive recordings. In lesional TLE, MEG could clarify the spatial relationship of the structural lesion to the irritative zone. Evaluation of patients with persistent seizures after epilepsy surgery may represent another clinical important application of MEG because magnetic fields are less influenced than electric fields by the prior operation. Simultaneous MEG and invasive EEG recordings indicate that epileptic activity restricted to mesial temporal structures cannot reliably be detected on MEG and that an extended cortical area of at least 6 to 8 cm2 involving also the basal temporal lobe is necessary to produce a reproducible MEG signal. In lateral neocortical TLE MEG seems to be more sensitive than scalp-EEG which further underlines the potential role of MEG for the study of nonlesional TLE. Whole-head MEG therefore can be regarded as a valuable and clinically relevant noninvasive method for the evaluation of patients with TLE.