Diffusion tensor imaging in temporal lobe epilepsy

Although mesial temporal sclerosis (MTS) has long been recognized in association with temporal lobe epilepsy (TLE), there is a growing body of literature suggesting structural abnormalities extending beyond the temporal lobe in patients with TLE. Diffusion tensor imaging (DTI) is a novel imaging technique that provides insight into the structural integrity of cerebral white matter. DTI studies have demonstrated extensive bilateral white matter abnormalities in TLE that extend far beyond the temporal lobe, even in patients with unilateral MTS. The relationship between white matter abnormalities, seizures, and comorbidity in TLE remains unclear.     

Thalamic diffusion and volumetry in temporal lobe epilepsy with and without mesial temporal sclerosis

PURPOSE: As an important connection within the limbic system, considerable attention has been paid to thalamic pathology in temporal lobe epilepsy (TLE). Magnetic resonance imaging (MRI) volumetric studies have yielded variable results and have largely been focused on TLE with mesial temporal sclerosis (TLE+). Diffusion tensor imaging (DTI) provides unique information on microstructure based on the measurement of water diffusion. To date, DTI properties of thalamus have not been well characterized in adult TLE patients with unilateral MTS or without MTS (TLE-). The purpose of this study was to investigate the status of thalamic integrity by using DTI as well as volumetric MRI in adult TLE+ and TLE- patients. METHOD: In 17 unilateral TLE+ patients, 10 TLE- patients and 26 controls, the thalamus was segmented by using an automated atlas-based method. Mean diffusivity (MD), fractional anisotropy (FA) and volume were then quantified from DTI and 3D T1-weighted scans. RESULTS: No significant changes were found in either DTI parameters or volume of thalamus in TLE- patients, as compared to healthy controls. However, both DTI parameters and MRI volumetry showed bilateral thalamic pathology in TLE+ patients, as compared to healthy controls. Also, TLE+ patients showed significant reduction of thalamic volume as compared to TLE- patients. In addition, thalamic FA ipsilateral to seizure focus showed significant correlation with age at onset of epilepsy in TLE+ patients. CONCLUSION: Our finding demonstrates bilateral pathology of thalamus in unilateral TLE+ patients. The discrepancy in thalamic pathology between TLE+ and TLE- patients suggests that along with differences in mesial temporal pathology, TLE+ and TLE- have unique extratemporal structural abnormalities.     

Unitemporal vs bitemporal hypometabolism in mesial temporal lobe epilepsy

BACKGROUND: Patients with mesial temporal lobe epilepsy (TLE) often show bilateral temporal hypometabolism (BTH), but the nature of this finding has not been well established. OBJECTIVE: To compare the clinical characteristics between unitemporal hypometabolism (UTH) and BTH patients in mesial TLE. DESIGN: Cross-sectional study. SETTING: Epilepsy center at university hospital in Seoul, Korea. PATIENTS: We enrolled 95 patients with mesial TLE, 87 of whom had subsequently undergone surgery. Seizures, interictal and ictal electroencephalography (EEG), brain magnetic resonance imaging, Wada test, and neuropsychological test results were reviewed. (18)F-fluorodeoxyglucose positron emission tomography scans were interpreted visually. Patients were divided into 2 groups: UTH and BTH. RESULTS: There were 59 UTH patients and 36 BTH patients. Semiologic analysis showed that UTH patients had higher frequencies of aura and unilateral dystonic posturing, whereas BTH patients had higher frequencies of a nonlateralized bilateral ictal EEG pattern and bilateral interictal spikes. Moreover, BTH patients had more frequent symmetric Wada memory scores and white matter changes in the bilateral temporal lobes on brain magnetic resonance imaging than UTH patients. All UTH patients with bilateral TLE on scalp EEG showed unilateral seizure onset on intracranial EEG. CONCLUSIONS: The characteristic clinical findings of mesial TLE with BTH were a more frequent nonlateralized ictal EEG pattern, bitemporal interictal spikes, symmetric Wada memory score, and the anterior temporal white matter changes, and less frequent aura and unilateral dystonic posturing. Surgical outcomes were similar and good in both groups, although surgery could not be performed in 8 BTH patients (22%).     

A meta-analysis of white matter changes in temporal lobe epilepsy as studied with diffusion tensor imaging

Purpose: Diffusion tensor imaging (DTI) is used increasingly to study white matter integrity in people with temporal lobe epilepsy (TLE). Most studies report fractional anisotropy (FA) decrease and mean diffusivity (MD) increase in multiple white matter regions. The disturbance of white matter integrity varies across studies and between regions. We aimed to obtain a more consistent estimate of white matter diffusion characteristics and relate these to the distance from the seizure focus. Methods: Studies comparing diffusion characteristics of people with epilepsy with those of healthy controls were systematically reviewed and quantified using random and mixed effects meta analysis. In addition to the overall meta‐analysis, pooled FA and MD differences were determined per hemisphere and white matter category separately. Key Findings: We included 13 cross‐sectional studies. The pooled FA difference for all white matter was ?0.026 (95% confidence interval [CI] ?0.033 to ?0.019) and MD difference was 0.028 × 10^?3 mm²/s (95% CI 0.015–0.04). FA was reduced significantly in people with TLE compared with healthy controls in both ipsilateral (mean difference ?0.03) and contralateral white matter (?0.02). MD was significantly increased ipsilaterally and contralaterally. MD differed significantly between white matter connected to the affected temporal lobe and remote white matter. Significance: The meta‐analysis provides a better estimation of the true diffusion characteristics. White matter structural integrity in TLE is disturbed more severely in the ipsilateral than in the contralateral hemisphere, and tracts closely connected with the affected temporal lobe are most disturbed. The exact underlying mechanisms remain to be elucidated.     

Ipsilateral and contralateral MRI volumetric abnormalities in chronic unilateral temporal lobe epilepsy and their clinical correlates

PURPOSE: To assess the presence, extent, and clinical correlates of quantitative MR volumetric abnormalities in ipsilateral and contralateral hippocampus, and temporal and extratemporal lobe regions in unilateral temporal lobe epilepsy (TLE). METHODS: In total, 34 subjects with unilateral left (n = 15) or right (n = 19) TLE were compared with 65 healthy controls. Regions of interest included the ipsilateral and contralateral hippocampus as well as temporal, frontal, parietal, and occipital lobe gray and white matter. Clinical markers of neurodevelopmental insult (initial precipitating insult, early age of recurrent seizures) and chronicity of epilepsy (epilepsy duration, estimated number of lifetime generalized seizures) were related to magnetic resonance (MR) volume abnormalities. RESULTS: Quantitative MR abnormalities extend beyond the ipsilateral hippocampus and temporal lobe with extratemporal (frontal and parietal lobe) reductions in cerebral white matter, especially ipsilateral but also contralateral to the side of seizure onset. Volumetric abnormalities in ipsilateral hippocampus and bilateral cerebral white matter are associated with factors related to both the onset and the chronicity of the patients' epilepsy. CONCLUSIONS: These cross-sectional findings support the view that volumetric abnormalities in chronic TLE are associated with a combination of neurodevelopmental and progressive effects, characterized by a prominent disruption in ipsilateral hippocampus and neural connectivity (i.e., white matter volume loss) that extends beyond the temporal lobe, affecting both ipsilateral and contralateral hemispheres.     

Diffusion tensor imaging findings and their correlation with neuropsychological deficits in patients with temporal lobe epilepsy and interictal psychosis

PURPOSE: To examine frontotemporal white-matter integrity in patients with temporal lobe epilepsy (TLE) and interictal psychosis. METHOD: Patients with TLE and interictal psychosis (IP; n = 20) were compared with age-matched TLE patients without psychosis (NIP; n = 20). Patients had either no focal lesions or hippocampal sclerosis on conventional MRI. Complete diffusion tensor imaging (DTI) data were available in 18 IP and 20 NIP patients. A region-of-interest (ROI) approach was used to determine the DTI measures, fractional anisotropy (FA) and mean diffusivity (MD), in the middle frontal and middle temporal gyri. The relation between the DTI measures and neuropsychological tests previously identified as impaired in the IP group was examined. RESULTS: The IP group had significantly lower FA values in both frontal and temporal regions and significantly higher MD in bilateral frontal regions. We found that performance on some neuropsychological tests was significantly related to frontotemporal FA reductions. CONCLUSIONS: Our findings suggest that subtle abnormalities in the frontotemporal white matter of patients with interictal psychosis may be undetectable on conventional MRI. These abnormalities may contribute to the cognitive deficits detected in these patients.     

Bilateral white matter diffusion changes persist after epilepsy surgery

PURPOSE: Bilateral white matter diffusion tensor imaging (DTI) abnormalities have been reported in patients with temporal lobe epilepsy (TLE) and unilateral mesial temporal sclerosis (MTS), but it is unknown whether these are functional or structural changes. We performed a longitudinal study in patients with unilateral MTS who were seizure-free for 1 year after surgery to determine whether the observed presurgical white matter diffusion abnormalities were reversible. METHODS: Eight TLE patients with unilateral MTS who were seizure-free after anterior temporal resection and 22 healthy subjects were recruited. DTI was performed before surgery and at 1-year follow-up. Tractography and region-of-interest (ROI) analyses were performed in the fornix, cingulum, genu, and splenium of the corpus callosum and external capsules. Diffusion tensor parameters were compared between groups and before and after surgery in the patient group. RESULTS: The fornix, cingulum, and external capsules showed preoperative bilateral abnormal diffusion parameters (i.e., decreased diffusion anisotropy and increased mean and perpendicular diffusivities). The fornix and cingulum ipsilateral to the resected mesial temporal structures showed signs of wallerian degeneration at 1-year follow-up. The contralateral tracts of the fornix, cingulum, and external capsules, as well as the genu of the corpus callosum, failed to show a normalization of their diffusion parameters. CONCLUSIONS: The irreversibility of the white matter DTI abnormalities on seizure freedom suggests underlying structural abnormalities (e.g., axonal/myelin degradation) as opposed to functional changes (e.g., fluid shifts due to seizures) in the white matter.     

Temporopolar changes in temporal lobe epilepsy: a quantitative MRI-based study

OBJECTIVES: To quantify the morphologic changes of temporopolar structures to better understand the pathophysiology of anterior temporal white matter increased T2 signal observed in temporal lobe epilepsy (TLE). METHODS: MRI was performed in 30 patients with TLE and in 30 normal control subjects and independently assessed by visual analysis and quantitative measurements. Specifically, the temporal pole (TP) volume, as well as its gray and white matter components, was measured using three-dimensional T1 MR images and a semiautomatic protocol. The authors tested whether the presence of an increased T2-weighted signal in the anterior temporal white matter was associated with significant TP atrophy. The associations between the TP volume and MRI signs of hippocampal sclerosis, age at onset, seizure frequency, duration of illness, and a history of febrile convulsions were also studied. RESULTS: Both right and left TLE populations demonstrated a reduction of the temporopolar white and gray matter volumes ipsilateral to seizure onset (p < 0.02 in right TLE; p < 0.0001 in left TLE). Twenty-two patients (72%) exhibited significantly abnormal TP volume measurements, which correctly lateralized the epileptogenic zone in all cases. The presence of an increased T2-weighted signal in the anterior temporal white matter (ISWM), but not that of hippocampal sclerosis, was associated with a greater TP volume asymmetry index (p < 0.05). CONCLUSIONS: The temporal pole is frequently atrophic ipsilateral to seizure onset in refractory TLE. The association between TP atrophy and ISWM suggests that both abnormalities might derive from a common pathologic process.     

The nature and extent of cerebellar atrophy in chronic temporal lobe epilepsy

Purpose: Research indicates that patients with chronic temporal lobe epilepsy (TLE) exhibit cerebellar atrophy compared to healthy controls, but the degree to which specific regions of the cerebellum are affected remains unclear. The purpose of this study was to characterize the extent and lateralization of atrophy in individual cerebellar lobes and subregions in unilateral TLE using advanced quantitative magnetic resonance imaging (MRI) techniques. Methods: Study participants were 46 persons with TLE and 31 age‐ and gender‐ matched healthy controls. All participants underwent high‐resolution MRI with manual tracing of the cerebellum yielding gray and white matter volumes of the right and left anterior lobes, superior posterior lobes, inferior posterior lobes, and corpus medullare. The degree to which asymmetric versus generalized abnormalities was evident in unilateral chronic TLE was determined and related to selected clinical seizure features (age of onset, duration of disorder). Key Findings: There were no lateralized abnormalities in cerebellar gray matter or white matter in patients with right or left TLE (all p’s > 0.2). Compared with controls, unilateral TLE was associated with significant bilateral reductions in the superior (p = 0.032) and inferior (p = 0.023) posterior lobes, whereas volume was significantly increased in the anterior lobes (p = 0.002), especially in patients with early onset TLE, and not significantly different in the corpus medullare (p = 0.71). Total superior cerebellar tissue volumes were reduced in association with increasing duration of epilepsy. Significance: Patients with unilateral TLE exhibit a pattern of bilateral cerebellar pathology characterized by atrophy of the superior and inferior posterior lobes, hypertrophy of the anterior lobe, and no effect on the corpus medullare. Cross‐sectional analyses show that specific aspects of cerebellar pathology are associated with neurodevelopmental (anterior lobe) or chronicity‐related (superior posterior lobe) features of the disorder.     

MRI analysis in temporal lobe epilepsy: cortical thinning and white matter disruptions are related to side of seizure onset

Purpose: Past studies reported more widespread structural brain abnormalities in patients with left compared to right temporal lobe epilepsy (TLE), but the profile of these differences remains unknown. This study investigated the relationship between cortical thinning, white matter compromise, epilepsy variables, and the side of seizure onset, in patients with TLE. Methods: We performed diffusion tensor imaging tractography and cortical thickness analyses of 18 patients with left TLE (LTLE), 18 patients with right TLE (RTLE), and 36 controls. We investigated the relationship among brain structural abnormalities, side of seizure onset, age of seizure onset, and disease duration. Key Findings: Patients with TLE displayed cortical thinning and white matter compromise, predominately on the side ipsilateral to the seizure onset. Relative to RTLE, patients with LTLE showed more widespread abnormalities, particularly in white matter fiber tracts. Greater compromise in white matter integrity was associated with earlier age of seizure onset, whereas cortical thinning was marginally associated with disease duration. Significance: These data support previous findings of LTLE showing greater structural compromise than RTLE, and suggest that mechanisms may not be uniform for gray and white matter compromise in patients with LTLE and RTLE. These results may indicate that LTLE is different from RTLE, possibly due to greater vulnerability of the left hemisphere to early injury and the progressive effects of seizures.     

White matter integrity correlates with depressive symptomatology in temporal lobe epilepsy

RationaleWhite matter abnormalities occur in both temporal lobe epilepsy (TLE) and depression, but there is limited research examining the depression–white matter association in depressed individuals with TLE. This study examined the relationship between white matter integrity (WMI) and depression including the influence of age at seizure onset, in adults with TLE, TLE and depression, and depression only.MethodsThirty-one adults were in one of three groups: TLE without depression (TLE; n = 11), TLE with depression (TLE + DEP; n = 9), and depression without TLE (DEP; n = 11). Participants completed structured interviews for depression diagnosis and severity. White matter integrity was estimated based on fractional anisotropy (FA) calculated in frontotemporolimbic (FTL) and non-FTL regions in the JHU DTI atlas.ResultsIn adults with TLE (n = 20), depressive symptomology was significantly correlated with FA in non-FTL regions and trended toward significance in FTL regions. These associations were found in FTL (statistically significant) and non-FTL (trended toward significance) regions in participants with childhood seizure onset but not in those with adolescent/adult seizure onset.ConclusionsCurrent results suggest that WMI, within FTL and non-FTL regions, are associated with depressive symptomology in adults with TLE. This association may be most notable in those with childhood-onset epilepsy. These findings could have important implications for the conceptualization and clinical care of neuropsychiatric comorbidities in TLE.     

Extratemporal white matter abnormalities in mesial temporal lobe epilepsy demonstrated with diffusion tensor imaging

PURPOSE: Recent studies have demonstrated bilateral white matter abnormalities in temporal lobe epilepsy (TLE) patients with unilateral mesial temporal sclerosis (MTS). The purpose of this project was to determine whether abnormalities of water diffusion are seen in extratemporal white matter of patients with TLE and pathologically confirmed MTS and to determine whether these findings are associated with worse surgical outcome. METHODS: Eleven patients with TLE and unilateral MTS confirmed in surgical specimens and 14 controls were studied by using cerebrospinal fluid-suppressed diffusion tensor imaging (DTI) and T2 relaxometry. RESULTS: Hippocampal T2 signal for patients was significantly elevated both ipsilateral (p<0.001) and contralateral (p=0.006) to MTS. DTI demonstrated reduced fractional anisotropy of the genu of the corpus callosum (p=0.003) and external capsule (p=0.02) and elevated mean diffusivity of the genu (p=0.005), splenium (p=0.03), and external capsule (p<0.001). For both the genu and external capsule, parallel diffusion of patients was not different from that of controls (genu, p=0.81; external capsule, p=0.45), whereas perpendicular diffusion was elevated (genu, p=0.001; external capsule, p<0.001). With mean postsurgical follow-up of 18.5 months, eight of 11 patients were entirely seizure free and the remaining three had all experienced a worthwhile reduction in seizure frequency. CONCLUSIONS: Our findings suggest that although patients with TLE and MTS have extensive bilateral and extratemporal pathology, these findings may not be associated with a worse postsurgical outcome.     

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.     

Interictal 99mTc-HMPAO SPECT in temporal lobe epilepsy: relation to clinical variables

PURPOSE: Factors affecting blood flow observed by interictal single-photon emission computed tomography (SPECT) images in temporal lobe epilepsy (TLE) have not been systematically studied or consistently demonstrated. We evaluated interictal SPECT results with respect to many clinical variables in a large population of TLE patients, all of whom underwent temporal lobectomy. METHODS: Interictal 99mTc-HMPAO SPECT scans from 61 TLE patients were obtained before an anterior temporal lobectomy. SPECT was analyzed using a region of interest analysis (ROI) in the cerebellum, anterior temporal lobe, lateral temporal lobe, mesial temporal lobe, whole temporal lobe, and inferior frontal lobe. Asymmetry indices (AIs) were calculated. Correlative analysis of AIs and clinical variables was performed. RESULTS: The AIs from TLE patients differed significantly from those of controls in the anterior temporal (p < 0.01), lateral temporal (p < 0.001), and whole temporal (p < 0.01) regions. No consistent overall correlation between the AIs and clinical variables existed. In right TLE (RTLE) only, AIs in the lateral and whole temporal lobe were positively correlated with age of onset (r = 0.470, p < 0.05; r = 0.548, p < 0.01, respectively). Similarly, in RTLE only, duration of epilepsy was negatively correlated with the anterior (r = -0.395, p < 0.05) and mesial (r = -0.45, p < 0.05) temporal lobe AI. No correlations were found between clinical variables and AIs in left TLE (LTLE) patients. CONCLUSIONS: Significant correlation of age at onset and duration of epilepsy with AIs in RTLE but not LTLE suggests physiologic processes may be determined in part by laterality of TLE. Clinical applications are problematic.     

Distribution of regional gray matter abnormalities in a pediatric population with temporal lobe epilepsy and correlation with neuropsychological performance

OBJECTIVE: The goals of the work described here were to determine if hippocampal and extrahippocampal atrophy in children with temporal lobe epilepsy (TLE) follows a pattern similar to that in adult patients, and to assess the clinical and neuropsychological relevance of regional brain atrophy in pediatric TLE. METHODS: Children with symptomatic TLE (n=14: 9 with mesial TLE due to hippocampal atrophy and 5 with TLE due to neocortical lesions), healthy children (n=14), and 9 adults with mesial temporal lobe epilepsy (MTLE) were compared using voxel-based morphometry (VBM) of brain magnetic resonance imaging (MRI). The children underwent a comprehensive neuropsychological battery. RESULTS: Children with MTLE with unilateral hippocampal atrophy (n=9) exhibited a significant reduction in gray matter in the hippocampus ipsilateral to the seizure origin and significant atrophy in the ipsilateral cingulate gyrus and contralateral middle frontal lobe. Children with TLE (n=14) exhibited a significant reduction in the gray matter of the ipsilateral hippocampus and parahippocampal gyrus. There was a correlation between gray matter volume in children with TLE and scores on several neuropsychological tests. Atrophy in pediatric patients with MTLE was less extensive than that in adults, and involved the hippocampi and the frontal cortex. CONCLUSIONS: Similar to adult MTLE, pediatric MTLE is associated with hippocampal and extrahippocampal cell loss. However, children display less intense quantifiable gray matter atrophy, which affects predominantly frontal lobe areas. There was a significant association between volume of gray matter in medial temporal and frontal regions and scores on neuropsychological tests. In childhood, TLE and the concomitant cognitive/behavior disturbances are the result of a damaged neural network.     

The neurobiology of cognitive disorders in temporal lobe epilepsy

Cognitive impairment, particularly memory disruption, is a major complicating feature of epilepsy. This Review will begin with a focus on the problem of memory impairment in temporal lobe epilepsy (TLE). We present a brief overview of anatomical substrates of memory disorders in TLE, followed by a discussion of how our understanding of these disorders has been improved by studying the outcomes of anterior temporal lobectomy. The clinical efforts made to predict which patients are at greatest risk of experiencing adverse cognitive outcomes following epilepsy surgery are also considered. Finally, we examine the vastly changing view of TLE, including findings demonstrating that anatomical abnormalities extend far outside the temporal lobe, and that cognitive impairments extend beyond memory function. Linkage between these distributed cognitive and anatomical abnormalities point to a new understanding of the anatomical architecture of cognitive impairment in epilepsy. Clarifying the origin of these cognitive and anatomical abnormalities, their progression over time and, most importantly, methods for protecting cognitive and brain health in epilepsy, present a challenge to neurologists.     

Wisconsin Card Sorting performance in patients with temporal lobe epilepsy: clinical and neuroanatomical correlates

PURPOSE: A sizable proportion of patients with temporal lobe epilepsy (TLE) display impairments on tests of executive function. Previous studies have suggested several factors that may explain such performance, including the presence of hippocampal sclerosis, electrophysiological disruption to extratemporal regions, and early age of seizure onset. However, no clear determinants have been found that consistently explain such executive dysfunction. The present study investigated the contribution of several clinical variables and temporal lobe neuroanatomic features to performance on the Wisconsin Card Sorting Test (WCST) in a series of patients with TLE. METHODS: Eighty-nine patients with lateralized TLE (47 left, 42 right) were examined. Seventy-two patients from this series underwent anterior temporal lobectomy (ATL). Regression analysis was used to examine the effects of age, education, age at seizure onset, seizure duration, seizure laterality, history of secondary generalized seizures, and MRI-based volumes of the right and left hippocampi on preoperative WCST performance (number of categories completed, perseverative errors). Further univariate analyses examined whether the presence of bilateral hippocampal sclerosis, mesial temporal lobe abnormalities beyond the hippocampus, or temporal neocortical abnormalities affected preoperative WCST performance. In addition, we examined whether becoming seizure free after ATL affected change in WCST performance. RESULTS: Overall regression analysis was not significant. However, an examination of individual partial correlations revealed that patients with a history of secondary generalized seizures performed more poorly on the preoperative WCST than did patients without such history. In addition, patients who were seizure free after ATL did not exhibit better WCST outcome than patients who did not become seizure free. The presence of bilateral hippocampal sclerosis, extrahippocampal mesial temporal atrophy, or temporal neocortical lesions did not affect WCST performance. CONCLUSIONS: These results indicate that the presence of temporal lobe structural abnormalities do not significantly affect executive function as measured by the WCST. The present study does suggests that the critical determinants of WCST performance in patients with TLE lie outside the temporal lobe and likely relate to metabolic disruption to frontostriatal neural network systems.     

颞叶癫癎弥散张量成像的影像学特征

颞叶癫癎（TLE）作为常见的一类局限性癫癎,了解其颅内病灶至关重要。MR弥散张量成像是一种水弥散成像技术,能够反映白质纤维的解剖和病理过程。本文介绍了TLE在弥散张量成像中的影像学表现：TLE患者病灶侧海马,与致癎灶相关连接结构如穹窿、扣带回、胼胝体和额颞叶联系纤维在弥散张量成像中均有异常信号,另外在双侧丘脑、额枕叶、双侧小脑亦有异常信号发现。TLE患者颅内各类白质纤维的信号异常与患者的某些认知功能有关。     

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.     

颞叶内侧结构弥散张量成像及白质纤维束成像在颞叶癫痫诊断中的应用价值

目的 通过磁共振弥散张量成像(DTI)及白质纤维束示踪(DTT)技术定量分析颞叶癫痫患者双侧颞叶内侧结构弥散参数值及局部纤维束变化特点,评价DTI技术对颞叶癫痫的诊断价值.方法 对广州医学院第二附属医院自2010年12月至2011年2月临床诊断为颞叶癫痫的16例患者和20例健康志愿者进行常规MRI及DTI扫描,测量双侧颞叶杏仁体、海马及颞叶皮质的部分各向异性(FA)、相对各向异性(RA)、表观弥散系数(ADC)等数值并进行统计学分析,同时应用DTT技术观察癫痫患者局部纤维束与正常对照者的差异.结果 正常对照者双侧颞叶内侧各结构FA、RA、ADC值比较差异均无统计学意义(P＞0.05).颞叶癫痫患侧、对侧与正常对照者颞叶内侧各结构FA、RA、ADC值比较差异均有统计学意义(P＜0.05),其中ADC值呈颞叶癫痫患侧＞颞叶癫痫对侧＞正常对照者的变化趋势,以海马尾部变化最为显著;而FA、RA值呈颞叶癫痫患侧＜颞叶癫痫对侧＜正常对照者的变化趋势,并且杏仁体、海马体部变化较海马尾部更显著.结论 DTI技术能充分了解癫痫患者颞叶内侧结构的弥散参数值及纤维束变化特点,有助于癫痫病灶定位的准确诊断,同时加深对颞叶内侧结构整体变化的了解亦有助于术前的整体评估及提高手术疗效.