MRI lesion and epileptogenic focus in temporal lobe epilepsy

The spatial relationship between a circumscribed lesion in the temporal lobe detected by MRI and an epileptogenic focus identified by ictal depth EEG along with a correlation of the MRI lesion with neuropathological findings were investigated in patients with medically intractable temporal lobe epilepsy but without any focal lesion on CT. Four parameters (an areal ratio of the temporal lobe against the hemisphere, area and calculated T1, T2 values of the hippocampus) were used to determine the abnormal MRI side. An agreement was reached in 67-72% of 18 patients between the abnormal values of the hippocampal area and of calculated T1, T2 and the side of the epileptogenic focus. In 14 of 17 patients, typical hippocampal sclerosis was demonstrated in resected tissue in accordance with the MRI lesions (atrophy and/or prolonged T2 of hippocampus). These results imply: 1) MRI abnormality thus defined may, if not all, indicate the side of the epileptogenic focus, and 2) also the presence of hippocampal sclerosis. It was emphasized that the MRI lesion would be a usable instrument to explore the causal relationship of hippocampal sclerosis to a generation of epileptogenic lesions as well as for presurgical evaluation.     

Hippocampal sclerosis can be reliably detected by magnetic resonance imaging

Two independent blinded observers reported the preoperative MRIs in a series of 81 consecutive patients with intractable temporal lobe epilepsy who were undergoing temporal lobectomy. We then compared the nature and lateralization of the MRI abnormalities with the pathologic diagnosis and the side of lobectomy. The MRI criteria of hippocampal sclerosis were an increased T2-weighted signal and the signal's confinement to a unilaterally small hippocampus. Imaging was performed in coronal and axial planes, specially orientated along and perpendicular to the long axis of the hippocampal body. We found diagnostic MRI abnormalities in 25 of the 27 cases with pathologically proven hippocampal sclerosis (sensitivity 93%, specificity 86%). In addition, we detected all 13 foreign tissue lesions on MRI. Overall, we detected lateralized lesions on MRI that correctly predicted the side of the epileptogenic temporal lobe in 72 cases (89%), with 2 possible errors. A learning effect in appreciating the relatively subtle MRI changes of hippocampal sclerosis was apparent in our later cases, as shown by an improved correlation between the 2 observers. This study demonstrates that hippocampal sclerosis can be identified on MRI with a high degree of sensitivity and specificity.     

Spectroscopic metabolic abnormalities in mTLE with and without MRI evidence for mesial temporal sclerosis using hippocampal short-TE MRSI

PURPOSE: Long echo time (TE) spectroscopy reliably identifies the epileptogenic hippocampus in mesial temporal lobe epilepsy. Short-TE spectroscopy gives additional metabolic information but may have more artifacts. The aim of this study was to test (a) lateralization of the seizure focus by short-TE spectroscopy, and (b) value of myoinositol (MI) in the identification of the epileptogenic hippocampus. METHODS: Twenty-four patients with temporal lobe epilepsy: 16 with mesial temporal sclerosis (TLE-MTS), eight patients with normal magnetic resonance imaging (MRI; TLE-No), and 16 controls were studied with hippocampal 2D short-TE magnetic resonance spectroscopic imaging (MRSI). RESULTS: In TLE-MTS, the ipsilateral N-acetylaspartate (NAA) was decreased compared with contralateral (p = 0.03) or controls (p = 0.007). Additionally, the ipsilateral MI was decreased compared with controls (p = 0.012). TLE-No values showed no side differences and were not different from controls. Abnormalities in the anterior hippocampus correctly lateralized the epileptogenic hippocampus in 相似文献   

Focal CT abnormality and epileptogenic focus

In 31 patients with temporal lobe epilepsy, the precise site of epileptogenic focus was determined by means of a depth EEG recording as one of the presurgical evaluations. In 13 patients, a CT scan revealed focal lesions; 7 in the left temporal lobe and 6 in the right temporal lobe. In 5 of the 7 patients and in 5 of the 6 patients the epileptogenic foci were determined in the temporal lobe on the side of a CT lesion. However, in 2 of the patients with a CT lesion in the left temporal lobe, independent epileptogenic foci were found in both the temporal lobes, and in the other patient with a CT lesion in the right temporal lobe, they were found in the right frontal and left temporal lobes. Thus, the CT lesions agreed in lateralization and focality with the epileptogenic foci in 10 of the 13 patients (77%), but they disagreed in 3 (23%). A CT lesion disclosed in the temporal lobe does not necessarily indicate the side and/or site where the epileptogenic focus may be localized. Although exceptions may be made, spatial disagreement was exemplified between the CT lesion and epileptogenic focus. Therefore, extreme caution has to be taken on the side and/or site of the epileptogenic focus when functional surgical indication is to be made.     

Focal CT Abnormality and Epileptogenic Focus

Abstract: In 31 patients with temporal lobe epilepsy, the precise site of epileptogenic focus was determined by means of a depth EEG recording as one of the presurgical evaluations. In 13 patients, a CT scan revealed focal lesions; 7 in the left temporal lobe and 6 in the right temporal lobe. In 5 of the 7 patients and in 5 of the 6 patients the epileptogenic foci were determined in the temporal lobe on the side of a CT lesion. However, in 2 of the patients with a CT lesion in the left temporal lobe, independent epileptogenic foci were found in both the temporal lobes, and in the other patient with a CT lesion in the right temporal lobe, they were found in the right frontal and left temporal lobes. Thus, the CT lesions agreed in lateralikeation and focality with the epileptogenic foci in 10 of the 13 patients (77%), but they disagreed in 3 (23%). A CT lesion disclosed in the temporal lobe does not necessarily indicate the side and/or site where the epileptogenic focus may be localized. Although exceptions may be made, spatial disagreement was exemplified between the CT lesion and epileptogenic focus. Therefore, extreme caution has to be taken on the side and/or site of the epileptogenic focus when functional surgical indication is to be made.     

Medial Temporal Lobe Heterotopia as a Cause of Increased Hippocampal and Amygdaloid MRI Volumes

Magnetic resonance imaging (MRI)–based volumetric measurements of the hippocampus and amygdala are useful in detecting hippocampal and amygdaloid sclerosis in patients with temporal lobe epilepsy. In these pathological entities, volumetric MRI analysis shows the epileptogenic structures to be atrophic when compared to the normal, nonepileptogenic side. Described are 2 patients with increased hippocampal and amygdaloid volumes on the side of seizure onset due to medial temporal lobe heterotopias. Care must be taken in the interpretation of volumetric MRI data to make certain that asymmetries in hippocampal and amygdaloid measurements are due to atrophy and sclerosis of the abnormal side and not to increased tissue such as heterotopic gray matter.     

术中高场强MRI辅助显微外科手术治疗颞叶癫痫

目的探讨应用术中高场强MRI辅助显微外科手术治疗颞叶癫痫的效果。方法2011年6月至2012年4月,对结构性异常的颞叶癫痫患者18例,利用1．5T高场强MRI实时辅助,术前术中常规行T、T2及T1加权、弥散张量成像检查,以确定显微手术切除范围及功能区。结果术后病检结果示右侧颞叶海绵状血管瘤2例,左侧颞叶海绵状血管瘤3例,右侧颞叶弥漫性少枝星形细胞瘤2例,左侧海马硬化4例,右侧海马硬化6例,左侧颞叶胚胎发育不良性神经上皮肿瘤1例。术后复查MRI手术切除满意,无手术并发症。术后随访2个月．1年,EngelⅠ级14例,Ⅱ级4例。结论术中1．5T高场强MRI辅助显微外科手术治疗结构性异常的颞叶癫痫,可以较完全切除致痫灶,并保护神经功能,手术安全和效果好。     

颞叶癫痫患者磁共振质子波谱与脑电图的关系

目的 探讨颞叶癫痫患者的磁共振质子波谱(1H-MRS)与动态脑电图和MRI之间的关系.方法 对入组的38例颞叶癫痫患者均行1H-MRS、常规MRI和动态脑电图检测,以16例健康儿童作为对照.根据MRI结果进行分组:单、双侧海马硬化组及非海马硬化组,计算各组病灶侧和病灶对侧的NAA/(Cr+Cho)、NAA/Cr和NAA/Cho并进行比较,同时分析脑电图中癫痫样放电情况.结果 38例患者中有14例MRI发现海马硬化(比例 为36.8%),31例1H-MRS异常(比例为81.6%),双侧、单侧海马硬化组病灶侧和病灶对侧及非海马硬化组病灶侧的上述3个指标均高于正常对照组(P＜0.05);38例患者中有27例动态脑电图异常,27例动态脑电图异常中有17例与1H-MRS的定位一致,二者的符合率为62.9%.结论 1H-MRS较MRI诊断海马硬化及对癫痫灶定侧的敏感性高;1H-MRS和动态脑电图在癫痫灶的定位中具有一致性.     

Hemicranial Volume Deficits in Patients with Temporal Lobe Epilepsy With and Without Hippocampal Sclerosis

Summary: Purpose: In patients with refractory temporal lobe epilepsy, studies have suggested volume deficits measured by MRI of brain structures outside the epileptogenic hippocampus. Hippocampal sclerosis (HS) is a frequent, but not obligate, finding in such patients. The present study examines the influence of the presence of HS on quantitative magnetic resonance imaging (MRI) measurements.
Methods: We analyzed 47 patients and 30 controls by quantitative MRI, including intracranial volume (ICV), hemicranial volume, hippocampal volume (HCV), and T₂relaxometry. MRI results were compared with histological findings in the resected temporal lobe.
Results: Histology documented HS in 35 patients (HS group) and other findings in 12 patients (no-HS group). In both groups, the hemicranial volume ipsilateral to the epileptogenic focus was significantly smaller than on the contralateral side (p <0.004). The HCV on both sides was smaller in the HS group compared with patients without HS (p ≥ 0.004). Unilateral hippocampal atrophy and increased T, value were found in 71% of patients with HS, and bilaterally normal HCV and T, value were found in 67% of patients without HS.
Conclusions: The smaller hemicranial volume on the focus side, irrespective of the presence or absence of HS suggests a different pathogenic mechanism for the additional hemicranial volume deficit, compared to HS itself. The contralateral HCV deficit depends on the presence of HS, indicating a pathogenic connection between damage to both hippocampi.     

When should a resection sparing mesial structures be considered for temporal lobe epilepsy?

Anteromesial temporal lobectomy (AMTL) is an effective and safe treatment for refractory temporal lobe epilepsy (TLE) caused by hippocampal sclerosis (HS). It is possible that modifications to this procedure could offer improved seizure control or a reduction in functional consequences in some patients. Reviewed here is the issue of when it might be appropriate to perform a resection for TLE that spares the mesial structures, particularly the hippocampus and parahippocampal gyrus. This issue is particularly important for dominant hemipshere TLE and for patients without obvious HS, as these are the patients at greatest risk for verbal memory decline following AMTL. Current evidence suggests that mesial structure-sparing resections may be worth consideration for two types of patients: those with temporal lobe foreign tissue lesions outside the mesial structures, and those with temporal lobe hypometabolism on fluorodeoxyglucose positron emission tomography but a normal MRI. Patients with dual pathology (i.e., HS plus another epileptogenic lesion) are unlikely to benefit from a resection that spares the mesial temporal lobe. There is little evidence to state whether resections of this kind are worthwhile for cryptogenic TLE, or for mesial TLE with preserved memory function. There is a clear need to move beyond the field's present focus on the hippocampus and investigate new approaches to TLE that may minimize the risks of functional consequences in patients without HS.     

Spectral Analysis of Sphenoidal Evoked Potentials Predicts Epileptic Focus

Sphenoidal evoked potentials (SpEPs) were recorded in 14 patients with intractable temporal lobe epilepsy. Twelve patients had electrographically proven unilateral seizure onset (five left, seven right). Two patients had partial complex seizures and unilateral mesial temporal lobe lesions shown by magnetic resonance imaging (MRI). Thirteen patients subsequently underwent temporal lobectomy. SpEPs were recorded using the P3 tonal oddball paradigm from sphenoidal electrodes referenced to scalp electrodes (i.e., T3, T4, C3, C4, Cz) and were subjected to spectral analysis for whole band (1-12.6 Hz) power. A significant relationship was found for side of seizure focus and reduced spectral power of the sphenoidal-temporal target SpEPs. In 10 of 14 patients, SpEP spectral power was less from the "epileptogenic" than from the "nonepileptogenic" temporal lobe. Of the remaining 4 patients, 2 had bilaterally equal spectral power, and 2 had lower SpEP power from the nonepileptogenic side. Postoperatively, all 13 patients are seizure-free except for the 2 patients with reduced SpEP power opposite to the ictal onset and 1 patient with fluctuations in SpEP asymmetries. Spectral analysis of SpEPs appears to have utility in the assessment of temporal lobe dysfunction and thus in the preoperative evaluation for epilepsy surgery.     

T2 hyperintense signal in patients with temporal lobe epilepsy with MRI signs of hippocampal sclerosis and in patients with temporal lobe epilepsy with normal MRI

BackgroundIncreased MRI T2 signal is commonly present not only in the hippocampus but also in other temporal structures of patients with temporal lobe epilepsy (TLE), and it is associated with histological abnormalities related to the epileptogenic lesion.ObjectiveThis study aimed to verify the distribution of T2 increased signal in temporal lobe structures and its correlations with clinical characteristics of TLE patients with (TLE-HS) or without (TLE-NL) MRI signs of hippocampal sclerosis.MethodsWe selected 203 consecutive patients: 124 with TLE-HS and 79 with TLE-NL. Healthy controls (N = 59) were used as a comparison group/comparative group. T2 multiecho images obtained via a 3-T MRI were evaluated with in-house software. T2 signal decays were computed from five original echoes in regions of interest in the hippocampus, amygdala, and white matter of the anterior temporal lobe. Values higher than 2 standard deviations from the mean of controls were considered as abnormal.ResultsT2 signal increase was observed in the hippocampus in 78% of patients with TLE-HS and in 17% of patients with TLE-NL; in the amygdala in 13% of patients with TLE-HS and in 14% of patients with TLE-NL; and in the temporal lobe white matter in 22% of patients with TLE-HS and in 8% of patients with TLE-NL. Group analysis demonstrated a significant difference in the distribution of the T2 relaxation times of the hippocampus (ANOVA, p < 0.0001), amygdala (p = 0.003), and temporal lobe white matter (p < 0.0001) ipsilateral to the epileptogenic zone for patients with TLE-HS compared with controls but only for the amygdala (p = 0.029) and temporal lobe white matter (ANOVA, p = 0.025) for patients with TLE-NL compared with controls. The average signal from the hippocampus ipsilateral to the epileptogenic zone was significantly higher in patients with no family history of epilepsy (two-sample T-test, p = 0.005).ConclusionIncreased T2 signal occurs in different temporal structures of patients with TLE-HS and in patients with TLE-NL. The hippocampal hyperintense signal is more pronounced in patients without family history of epilepsy and is influenced by earlier seizure onset. These changes in T2 signal may be associated with structural abnormalities related to the epileptogenic zone or to the nature of the initial precipitating injury in patients with TLE.     

Magnetic resonance imaging in intractable partial epilepsy: correlative studies

A study was performed evaluating magnetic resonance imaging (MRI) in 35 patients with intractable complex partial seizures in whom computed tomographic (CT) scans showed no focal abnormalities. These results were correlated with positron emission tomography evaluation (PET), the electroencephalographic ictal onset, and findings during pathological examination. Seven patients had structural lesions that were epileptogenic, detected by MRI; the lesions were tuberous sclerosis, astrocytomas, or hamartomas. Three of these 7 patients underwent PET scanning, which was normal in all. Of 18 patients with mesial temporal sclerosis, 10 were shown by PET to have temporal lobe hypometabolism, though all 18 had normal MRI findings. The results indicate that MRI contributes information to that provided by CT and PET, by detecting nonsclerotic epileptogenic lesions of the temporal lobe.     

颞叶癫癎21例手术治疗分析

目的探讨颞叶癫癎的外科治疗方法及效果.方法 21例颞叶癫癎患者,术前均行EEG、MRI检查,其中6例行PET检查,经定侧定位后,行手术治疗.其中13例行标准前颞叶切除术,5例行病灶切除+致癎灶切除,3例行选择性海马杏仁核切除.术中应用皮层电极或深部电极进行监测;神经导航下海马钙化切除1例.结果术后无明显并发症,均取得满意近期效果.结论海马硬化是颞叶癫癎发生的主要原因;手术是治疗颞叶癫癎的重要手段,且疗效满意.     

Lateralization of epileptic foci by magnetic resonance imaging in temporal lobe epilepsy.

A retrospective single-blind study was carried out to assess the reliability of magnetic resonance imaging (MRI) for determining lateralization of the electrographic focus in 45 patients with intractable temporal lobe epilepsy. With strictly defined MRI diagnostic criteria, the electroencephalographic (EEG) focus was correctly lateralized in 86% of patients. Excluding patients with structural lesions, the criteria provided for correct lateralization of the epileptogenic focus in 78% and false lateralization in 5%. Hippocampal atrophy on T1-weighted images and increased signal intensity from mesial structures on T2-weighted scans were highly reliable for lateralization. Postoperative outcome did not differ between the patients with normal and those with abnormal findings on MRI, but the group sample was inadequate to assess the issue of surgical outcome. These findings suggest that with appropriate techniques and strictly defined diagnostic criteria, MRI can provide reliable seizure lateralization in patients with intractable temporal lobe epilepsy.     

Temporal lobe epilepsy associated with cystic lesion in the temporal lobe and middle cranial fossa]

Four patients out of 52 patients with temporal lobe epilepsy (TLE), who underwent epilepsy surgery in our hospital since September of 1994, had cystic lesions in the temporal lobe and middle cranial fossa. Case 1 had old hematoma cavity in the inferior temporal gyrus and chronic subdural electrode recording revealed the ictal onset zone to be localized in the ipsilateral medial temporal region. Case 2 had cystic ganglioglioma in the temporal tip, and intraoperative electrocorticography demonstrated independent paroxysmal activities from medial temporal region and temporal tip near the cyst. Both area were resected and the patients became seizure free. Case 3 and 4 had arachnoid cysts in the middle cranial fossa. Chronic subdural electrode recording revealed that the ictal onset zone was localized in the ipsilateral inferior temporal gyrus (that had microdysgenesis) in Case 3 and contralateral medial temporal region (that had hippocampal sclerosis) in Case 4, respectively. These finding suggest that co-existence of extra-axial cyst such as Case 3 and 4 is incidental and that arachnoid cyst is less epileptogenic. However, intra-axial cyst such as Case 1 and 2 is epileptogenic and complicated physiological mechanism such as kindling phenomenon or secondary epileptogenesis may effect on the hippocampus. Comprehensive presurgical evaluation including electrocorticography is needed in the surgical treatment of TLE with cystic lesion.     

A Correlative Study between Hippocampal Atrophy Quantified by Tomo-Pneumoencephalography and Epileptogenic Focus in Temporal Lobe Epilepsy

It appeared certain that we can quantify the rate of hippocampal atrophy by utilizing the sagittal cuts in tomo-pneumoencephalog-raphy. This is a reliable method to infer the side of the epileptogenic focus in temporal lobe epilepsy since a close correlation was disclosed between the side with more atrophic features of the hippocampus and that of the epileptogenic focus explored by depth EEG, in particular, in the mesial temporal focus group. On the other hand, it seems to be plausible that the hippocampal atrophy could be secondarily induced by epileptic discharges in the lateral temporal group. Namely, controversies dealing with the casual relationship of hippocampal atrophy should be discussed based on the epileptogenic focus localization in temporal lobe epilepsy.     

A correlative study between hippocampal atrophy quantified by tomo-pneumoencephalography and epileptogenic focus in temporal lobe epilepsy

It appeared certain that we can quantify the rate of hippocampal atrophy by utilizing the sagittal cuts in tomo-pneumoencephalography. This is a reliable method to infer the side of the epileptogenic focus in temporal lobe epilepsy since a close correlation was disclosed between the side with more atrophic features of the hippocampus and that of the epileptogenic focus explored by depth EEG, in particular, in the mesial temporal focus group. On the other hand, it seems to be plausible that the hippocampal atrophy could be secondarily induced by epileptic discharges in the lateral temporal group. Namely, controversies dealing with the casual relationship of hippocampal atrophy should be discussed based on the epileptogenic focus localization in temporal lobe epilepsy.     

MRI in the presurgical evaluation of patients with frontal lobe epilepsy and children with temporal lobe epilepsy: pathologic correlation and prognostic importance.

We performed magnetic resonance imaging (MRI) using a high-field strength magnet (1.5 T) in two series of 53 patients with intractable partial epilepsy of frontal lobe or temporal lobe origin who subsequently received ablative surgery for their seizure disorder. In the first series of patients the pathologic correlation and prognostic importance of an MRI-identified lesion in the frontal lobe were assessed. Twenty-five percent of the patients with negative MRI studies and 67% of patients with neuroimaging abnormalities restricted to the frontal lobe, were seizure-free at a minimum duration of follow-up of 1 year. None of the patients with a multilobar MRI-detected abnormality was seizure-free postoperatively. In the second study the sensitivity and specificity of MRI-based hippocampal volumetry was determined in pediatric patients with partial epilepsy of temporal lobe origin unrelated to foreign-tissue pathology. Hippocampal formation atrophy in the epileptic temporal lobe was identified in 63% of patients. The sensitivity and specificity of hippocampal volumetry was 100% in patients with mesial temporal sclerosis. The presence of an MRI-detected epileptogenic lesion in the frontal lobe and hippocampal formation atrophy in the temporal lobe may correlate with the underlying pathology and affect the identification of potential candidates for epilepsy surgery.     

难治性颞叶癫痫的外科治疗(附35例临床分析)

目的总结并分析难治性颞叶癫痫患者术前定位、手术方式和经验。方法回顾性分析2009年6月至2011年6月,采用颞前叶+海马杏仁核切除术治疗的颞叶癫痫病人35例,其中术前MRI及术后病理证实伴有海马硬化者32例,所有病例术中均在皮层电极监测下切除颞叶皮质及同侧海马、杏仁核,手术后均应用抗癫痫药物治疗,术后随访1～3年。结果在35随访病例中,癫痫发作控制结果显示EngelⅠ级24例,Ⅱ级8例,Ⅲ级3例,Ⅳ级0例。其中有12例病人术后2年逐渐停用抗癫痫药物。结论联合应用VEEG、MRI及EcoG能准确确定致痫灶,提高颞叶癫痫手术疗效。手术方式选择及显微理念的应用,能有效减少术后并发症的发生,避免出现永久性神经功能缺失。