Correlation between inter-ictal regional cerebral blood flow and sphenoidal electrodes--recorded inter-ictal spikes in mesial temporal lobe epilepsy

The objective of this study was to assess the reliability of the diagnosis of mesial temporal lobe epilepsy using EEG and sphenoidal electrodes. Inter-ictal 99 m Tc-HMPAO SPECT scans were registered in 21 patients with confirmed mesial temporal lobe epilepsy identified by scalp EEG and sphenoidal electrodes. Visual and quantitative SPECT analysis was performed blind to EEG data. An asymmetry index (AI) was measured from the ratio of two symmetrical regions of interest. A temporal lobe hypoperfusion was defined as an uptake reduced by 5% with respect to the contralateral region. Inter-ictal SPECT abnormalities were observed in 12 out of 21 patients (57%) from both visual and quantitative analysis (focal hypoperfusion in 11 cases, focal hyperperfusion in one case). In seven patients (33%) both visual and quantitative scintigraphy were normal. Abnormal AI was found in 11/15 patients with a high frequency of seizures and in 1/6 patients with a low frequency of seizures. The major data is that the probability to have an abnormal SPECT is statistically correlated to the frequency of the epileptic fits. The couple EEG recordings with sphenoidal electrodes and SPECT is sensitive and reliable in the diagnosis of mesial temporal lobe epilepsy.     

Regional cerebral blood flow during interictal state: differences between temporal lobe epilepsy and primary generalized epilepsy

Regional cerebral blood flow (rCBF) was investigated during interictal state by 133Xenon intravenous clearance technique in two groups of epileptic patients: group I (n = 28) having partial complex seizures (temporal lobe epilepsy); group II (n = 14) having generalized seizures (primary generalized epilepsy). Mean hemispheric CBF was decreased in group I and unchanged in group II compared to normal controls. Modifications in rCBF pattern were observed in group I but not in group II. A marked hypoperfusion of one temporal region was found in patients from group I showing a unilateral and fixed epileptic focus. Hypoperfusion of other cerebral areas at a distance from the epileptic focus was greater for patients with a left epileptic focus than for those with a right epileptic focus. Patients with the same severity of disease and bilateral and variable foci had no significant modification of mean hemispheric CBF and rCBF distribution. These observations indicate that interictal investigations of rCBF may be of interest for a differential classification of epilepsy.     

Correlation between inter-ictal regional cerebral blood flow and sphenoidal electrodes - recorded inter-ictal spikes in mesial temporal lobe epilepsy

Abstract

The objective of this study was to assess the reliability of the diagnosis of mesial temporal lobe epilepsy using EEG and sphenoidal electrodes. Inter-ictal 99 m Tc-HMPAO SPECT scans were registered in 21 patients with confirmed mesial temporal lobe epilepsy identified by scalp EEG and sphenoidal electrodes. Visual and quantitative SPECT analysis was performed blind to EEG data. An asymmetry index (Al) was measured from the ratio of two symmetrical regions of interest. A temporal lobe hypoperfusion was defined as an uptake reduced by 5% with respect to the contralateral region. Inter-ictal SPECT abnormalities were observed in 12 out of 21 patients (57%) from both visual and quantitative analysis (focal hypoperfusion in 11 cases, focal hyperperfusion in one case). In seven patients (33%) both visual and quantitative scintigraphy were normal. Abnormal Al was found in 11/15 patients with a high frequency of seizures and in 1/6 patients with a low frequency of seizures. The major data is that the probability to have an abnormal SPECT is statistically correlated to the frequency of the epileptic fits. The couple EEG recordings with sphenoidal electrodes and SPECT is sensitive and reliable in the diagnosis of mesial temporal lobe epilepsy. [Neurol Res 2000; 22: 674-678]     

Patterns of postictal cerebral blood flow in temporal lobe epilepsy: qualitative and quantitative analysis

We used single-photon emission computed tomography (SPECT) to study postictal cerebral blood flow (CBF) in 51 patients with temporal lobe epilepsy. There were 78 seizures studied, 77 by early postictal injection of Tc-99m HMPAO (delay from seizure onset = 4.3 +/- 4.5 min) and one by ictal injection. Increased focal temporal lobe uptake, predominantly confined to the anteromesial region, was present in 83% and declined rapidly over 5 minutes. Reduced activity in the lateral temporal lobe accompanied the mesial increase in 80% of studies, extending over much of the ipsilateral hemisphere and closely associated with the degree and extent of postictal EEG slow waves. These patterns enabled correct seizure localization by blinded analysis in 69% (31/45) of the patients with a unilateral EEG focus. The remainder showed bilateral or no changes. One of six patients with bitemporal EEG foci had unilateral perfusion changes. The positive predictive value for the correct localization of a unilateral focus by postictal SPECT was 97% (31/32). Postictal CBF imaging with SPECT can be used to support noninvasive electrographic localization and may decrease the need for invasive electrode studies.     

Impaired cerebral blood flow networks in temporal lobe epilepsy with hippocampal sclerosis: A graph theoretical approach

Graph theory is an emerging method to investigate brain networks. Altered cerebral blood flow (CBF) has frequently been reported in temporal lobe epilepsy (TLE), but graph theoretical findings of CBF are poorly understood. Here, we explored graph theoretical networks of CBF in TLE using arterial spin labeling imaging. We recruited patients with TLE and unilateral hippocampal sclerosis (HS) (19 patients with left TLE, and 21 with right TLE) and 20 gender- and age-matched healthy control subjects. We obtained all participants' CBF maps using pseudo-continuous arterial spin labeling and analyzed them using the Graph Analysis Toolbox (GAT) software program. As a result, compared to the controls, the patients with left TLE showed a significantly low clustering coefficient (p = 0.024), local efficiency (p = 0.001), global efficiency (p = 0.010), and high transitivity (p = 0.015), whereas the patients with right TLE showed significantly high assortativity (p = 0.046) and transitivity (p = 0.011). The group with right TLE also had high characteristic path length values (p = 0.085), low global efficiency (p = 0.078), and low resilience to targeted attack (p = 0.101) at a trend level. Lower normalized clustering coefficient (p = 0.081) in the left TLE and higher normalized characteristic path length (p = 0.089) in the right TLE were found also at a trend level. Both the patients with left and right TLE showed significantly decreased clustering in similar areas, i.e., the cingulate gyri, precuneus, and occipital lobe. Our findings revealed differing left–right network metrics in which an inefficient CBF network in left TLE and vulnerability to irritation in right TLE are suggested. The left–right common finding of regional decreased clustering might reflect impaired default-mode networks in TLE.     

Interictal regional cerebral blood flow during non specific activation test in partial epilepsy.

In order to investigate, during activation testing, the interictal cortical cerebral blood flows (rCBF) of epileptic patients suffering from complex partial seizures, 40 epileptic patients (divided into "lesional", this is, with abnormal CT findings, and "non lesional", that is, with normal CT findings) were submitted to rCBF measurements with the 133 xenon intravenous technique, at rest and during intermittent light stimulation (ILS). The findings compared with normal volunteers seem to demonstrate that, during ILS, (1) in non lesional patients, the suspected epileptic focus shows a significant rCBF increase (2) in lesional patients, the significant rCBF increases were not in the region of the suspected epileptic focus but in adjacent or in contralateral ones. It was concluded that activation interictal rCBF measurements are more useful than resting ones for the determination of epileptic foci when CT findings are normal and that the nature of the epileptic focus influences markedly the interhemispheric activation pattern.     

Correlations between cerebral blood flow variations and clinical parameters in temporal lobe epilepsy: an interictal study.

Regional cerebral blood flow (rCBF) measurements were determined by the intravenous Xenon 133 technique in 80 patients suffering from temporal lobe epilepsy. All the patients had a normal CT scan. Three subgroups were differentiated, according to EEG and all-night polygraphic recordings: temporal lobe epilepsy with left (N = 25) or right (N = 25) EEG epileptic abnormalities and temporal lobe epilepsy with EEG abnormalities in both temporal regions with asynchronous occurrence (n = 30). In comparison with a control group (n = 20), there was (1) a marked reduction of blood flow in the temporal region corresponding to the site of the epileptic focus and (2) a reduction in blood flow in distant brain areas and the contralateral hemisphere. The rCBF decrease was highly correlated (p less than 0.001) with the disease severity (taking into account the complex partial seizure frequency and the number of secondary generalised seizures). Differences were found in the rCBF decrease between left and right temporal lobe epilepsy.     

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     

Reorganized cerebral metabolic interactions in temporal lobe epilepsy.

Patients with left temporal lobe epilepsy demonstrate language impairments that are not well understood. To explore abnormal patterns of brain functional connections with respect to language processing, we applied a principal component analysis to resting regional cerebral metabolic data obtained with positron emission tomography in patients with right- and left-sided temporal lobe epilepsy and controls. Two principal components were expressed differentially among the groups. One principal component comprised a pattern of metabolic interactions involving left inferior frontal and left superior temporal regions-corresponding to Broca's and Wernicke's areas, respectively-and right mesial temporal cortex and right thalamus. Functional couplings between these brain regions were abnormally enhanced in the left-sided epilepsy patients. The right thalamic left superior temporal coupling was also abnormally enhanced in the right-sided epilepsy patients, but differentially from that in the left-sided patients. The other principal component was characterized by a pattern of metabolic interactions involving right and left mid prefrontal and right superior temporal cortex. Although both the right- and left-sided epilepsy patients showed decreased functional couplings between left mid prefrontal and the other brain regions, a weaker right-left mid prefrontal coupling in the left-sided epilepsy patients best distinguished them from the right-sided patients. The two mutually independent, abnormal metabolic patterns each predicted verbal intelligence deficits in the patients. The findings suggest a site-dependent reorganization of two independent, language-subserving pathways in temporal lobe epilepsy.     

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.     

颞叶内侧癫癎发作期海马深部脑电图的特点

目的探讨颞叶内侧癫癎（medial temporal lobe epilepsy,MTLE）发作期海马深部脑电图的特点。方法回顾性分析记录双侧海马深部脑电图,行前颞叶切除术且长期预后良好的18例病人的临床资料,研究海马深部脑电图发作起源的波形特点和部位。结果发作期海马深部脑电图低幅快节律起源7例,棘（尖）波节律起源8例,高幅棘（尖）慢波起源占3例。起源点主要位于从海马头部向后3 cm之内的区域。结论低幅快节律、棘（尖）波节律是MTLE病人海马深部脑电图发作期的最主要两种波形。发作起源区主要位于海马前头部。     

Hippocampal neuronal loss and regional hypometabolism in temporal lobe epilepsy

The pathophysiology of widespread interictal hypometabolism in temporal lobe epilepsy is unknown but might reflect neuronal loss and diaschisis. We found no significant correlation between any cortical region's metabolism on preoperative {¹⁸F} fluorodeoxyglucose positron emission tomography and neuronal density of resected hippocampi in 40 patients. We conclude that hippocampal neuronal loss and diaschisis cannot account for the regional interictal hypometabolism of temporal lobe epilepsy.     

Human regional cerebral blood flow during rapid-eye-movement sleep

Owing to the coupling between CBF and neuronal activity, regional CBF is a reflection of neural activity in different brain regions. In this study we measured regional CBF during polysomnographically well-defined rapid-eye-movement (REM) sleep by the use of single photon emission computerized tomography and the new tracer 99mTc-dl-hexamethylpropyleneamine. Eleven healthy volunteers aged between 22 and 27 years were studied. CBF was measured on separate nights during REM sleep and during EEG-verified wakefulness. On awakening from REM sleep, all subjects reported visual dreams. During REM sleep CBF increased by 4% (p less than 0.01) in the associative visual area, while it decreased by 9% (p less than 0.01) in the inferior frontal cortex. The CBF increase in the associative visual area suggests that activation of cerebral structures processing complex visual material is correlated to visual dream experiences. On the other hand, the reduced involvement of the inferior frontal cortex observed during REM sleep might explain the poor temporal organization and bizarreness often experienced in dreams.     

颞叶癫痫患者脑内细胞凋亡现象的研究

目的探讨细胞凋亡在颞叶癫痫发病机制中的可能作用及意义。方法１５例颞叶癫痫患者为我院手术的病人,选取同一时期死于非神经系统疾病的５例患者作为对照。采用ＴＵＮＥＬ方法原位标记ＤＮＡ片段,观察这１５例颞叶癫痫患者手术切除的海马标本和５例死于非神经系统疾病患者的尸检的海马标本的细胞调亡现象。结果（１）ＴＵＮＥＬ阳性细胞在海马各个部位分布不均匀,有区域性差异。（２）在海马细胞层结构中,主要分布于ＣＡ１－ＣＡ３区的腔隙分子层及齿状回颗粒细胞层外侧。（３）颞叶癫痫患者海马ＣＡ３区ＴＵＮＥＬ阳性细胞平均百分率（５１．１９％）与死于非神经系统疾病患者的（１５．８％）比较有极显著性差异（Ｐ＜０．０１）,且与癫痫发作的病程、年龄及发作频率无关。结论细胞凋亡参与颞叶癫痫的发病过程,但可能并非其发病的特异性因素。     

Frontal lobe function in temporal lobe epilepsy

Temporal lobe epilepsy (TLE) is typically associated with long-term memory dysfunction. The frontal lobes support high-level cognition comprising executive skills and working memory that is vital for daily life functioning. Deficits in these functions have been increasingly reported in TLE. Evidence from both the neuropsychological and neuroimaging literature suggests both executive function and working memory are compromised in the presence of TLE. In relation to executive impairment, particular focus has been paid to set shifting as measured by the Wisconsin Card Sorting Task. Other discrete executive functions such as decision-making and theory of mind also appear vulnerable but have received little attention. With regard to working memory, the medial temporal lobe structures appear have a more critical role, but with emerging evidence of hippocampal dependent and independent processes. The relative role of underlying pathology and seizure spread is likely to have considerable bearing upon the cognitive phenotype and trajectory in TLE. The identification of the nature of frontal lobe dysfunction in TLE thus has important clinical implications for prognosis and surgical management. Longitudinal neuropsychological and neuroimaging studies assessing frontal lobe function in TLE patients pre- and postoperatively will improve our understanding further.     

Extratemporal lobe circuits in temporal lobe epilepsy

There is increasing interest in the functional anatomy of epilepsy with the goal to identify the critical nodes in the seizure circuits so that therapy can be directed at them. This goal is especially important because direct delivery of therapy, either through electrical stimulation, drug infusion, or molecular therapies such as optogenetics, has become increasingly possible. In this article, we will review the basic functional anatomy of mesial temporal lobe epilepsy and its primary subcortical connection, the medial dorsal nucleus of the thalamus. Based on its anatomical connections and known physiological interactions, we propose a key role for this thalamic nucleus that is essential for the development of seizures, and this role suggests that this region is a potential therapeutic target.This article is part of a Special Issue entitled “NEWroscience 2013”.     

Cerebral activation during speech discrimination in temporal lobe epilepsy

Eight patients with uncontrolled complex partial seizures underwent positron emission tomography with 18-fluoro-2-deoxyglucose both at rest and during an auditory order discrimination task using speech syllables. Eight age-matched controls were scanned under identical conditions; an additional 18 normal subjects were scanned only at rest. No consistent task-related changes were seen in control subjects. For the 3 patients with left temporal epileptogenic foci, left inferior temporal lobe hypometabolism was more evident during the activated than during the resting scan. Activation procedures may augment the diagnostic yield of metabolic scanning in epilepsy.     

Disparity in regional cerebral blood flow during electrically induced seizure

This is a presentation of 2 cases in which the intraictal regional cerebral blood flow distribution was measured with the ^99mTc-HMPAO single photon emission computerized tomography technique during an electrically induced seizure. Although the seizure was verified as generalized on electroencephalography, the regional neuronal activity expressed as rCBF unexpectedly was markedly asymmetrical in one of the cases. These findings demonstrated that the ^99mTc-HMPAO technique makes it possible to discriminate intraictal variation in cortical and subcortical activation between the hemispheres during electroencephalography-verified generalized seizures.