Gangliogliomas: characteristic imaging findings and role in the temporal lobe epilepsy

Introduction  Ganglioglioma is an uncommon neoplasm of the central nervous system, most frequently seen in the temporal lobe, and usually associated with medically refractory epilepsy in children and young adults. Few reports have considered ganglioglioma-associated epileptogenicity arising in the temporal lobe. The purpose of our study was to define the imaging features of ganglioglioma in the temporal lobe and their relation to the seizure foci revealed by electrocorticograms. Materials and methods  We reviewed 24 patients with pathologically confirmed ganglioglioma in the temporal lobe. Results  Computed tomography (CT) images showed gangliogliomas to be isodense (91.7%), and on T1-weighted images (T1-WI) most gangliogliomas (79.2%) were isointense to the gray matter. A cystic lesion was seen in 14 of 24 of the gangliogliomas (58.3%). Mass effects were not seen in any of the ten tumors without cystic components. One patient showed tumor recurrence. Dual pathology was seen in two cases (8.3%). In 23 cases, epileptogenicity was confirmed in the tumors by intraoperative electrocorticogram. The remaining case had no epileptogenicity. Conclusion  A tumor presenting isointensity to gray matter on T1-WI without mass effects in the medial temporal lobe in a young patient with temporal lobe epilepsy (TLE) might be the characteristic imaging of temporal lobe ganglioglioma. However, such tumors are not always associated with epileptogenicity, even if a ganglioglioma is found in a patient with TLE. The seizure foci may be contralateral to the ganglioglioma. Therefore, we need to investigate the hippocampus, white matter abnormalities of the ipsilateral and contralateral anterior temporal lobe, and other focal lesions closely.     

颞叶癫痫的MRI研究

研究颞叶癫痫患者的ＭＲＩ表现，并测量ＴＬＥ患者海马结构的体积以确定癫痫灶的侧别。在１．０ＴＭＲ机对３８例ＴＬＥ患者进行研究，用正中矢状面定位，作平行于脑干的倾斜冠状面Ｔ１和Ｔ２加权像。在所有的倾斜冠状面Ｔ１加权像上手工描出ＨＰＦ的边界，把所有层在的体积相加即得到ＨＰＦ的体积，并进行标准处理以消除头颅大小的影响。     

Degree of hippocampal atrophy is related to side of seizure onset in temporal lobe epilepsy

BACKGROUND AND PURPOSE: Temporal lobe epilepsy (TLE) is associated with pathologic changes in hippocampal physiology and morphology. Our aim was to quantify volume reduction of the right and left hippocampus in patients with TLE and to investigate whether the degree of hippocampal atrophy is related to the side of seizure onset. METHODS: The volume of the right and left hippocampus was estimated for 50 controls and 101 patients with TLE, by applying the unbiased Cavalieri method on MR images. RESULTS: Pairwise comparisons, within a multivariate analysis of variance and adjusted by using the Bonferroni correction, revealed that both right and left hippocampal volumes were, on average, significantly smaller in patients with right-sided seizure onset (R-patients) relative to those of controls (P < .001 and P = .04, respectively). Furthermore, left hippocampal volume was significantly smaller in patients with left-sided seizure onset (L-patients) compared with controls (P < .001), but the right-sided hippocampal volume was not significantly smaller (P = .71). Moreover, a correlation analysis revealed that the strong linear association between the right and left hippocampal volumes existing in the control population (r = 0.73) is partially lost in patients with TLE (r < or = 0.48), and this loss in correlation appears to be more pronounced in L-patients than in R-patients. CONCLUSION: Our MR imaging results suggest that although the major damage in patients with TLE is located in the hippocampus ipsilateral to the side of seizure onset, R-patients are more likely to have bilateral hippocampal volume reduction. These findings support the hypothesis that cerebral hemispheres may not only differ in their functionality organization but also in their vulnerability to a neurologic insult.     

Inter-modality comparisons of seizure focus lateralization in complex partial seizures.

Anterior temporal lobectomy offers a high chance of seizure-free outcome in patients suffering from drug-refractory complex partial seizure (CPS) originating from the temporal lobe. Other than EEG, several functional and morphologic imaging methods are used to define the spatial seizure origin. The present study was undertaken to compare the merits of fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET), magnetic resonance imaging (MRI) and single-voxel proton MR spectroscopy (MRS) for the lateralization of temporal lobe seizure foci. The clinical charts and imaging data of 43 consecutive CPS patients were reviewed. Based on surface EEG, 31 patients were classified with temporal lobe epilepsy (TLE; 25 lateralized, 6 not lateralized) and 12 with non-temporal lobe epilepsy. All were examined by FDG-PET, MRS and MRI within 6 weeks. FDG-PET and MRI were interpreted visually, while the N-acetyl-aspartate to creatine ratio was used for MRS interpretation. One FDG-PET scan was invalid due to seizure activity post injection. The MR spectra could not be evaluated in five cases bilaterally and three cases unilaterally for technical reasons. A total of 15 patients underwent anterior temporal lobectomy. All showed a beneficial postoperative outcome. When the proportions of agreement between FDG-PET (0.77), MRI (0.58) and MRS (0.56) and surface EEG in TLE cases were compared, there were no significant differences (P>0.10). However, FDG-PET showed a significantly higher agreement (0.93) than MRI (0.60; P=0.03) with the side of successful temporal lobectomy. The concordance of MRS with the side of successful temporal lobectomy was intermediate (0.75). When the results of functional and morphologic imaging were combined, no significant differences were found between the rates of agreement of FDG-PET/MRI and MRS/MRI with EEG (0.80 vs 0.68; P=0.50) and with the side of successful temporal lobectomy (0.87 vs 0.92; P=0.50) in TLE cases. However, MRS/MRI showed significantly more lateralized temporal lobe abnormalities in non-temporal lobe epilepsy cases than FDG-PET/MRI (0.90 vs. 0.17; P<0.01). Although FDG-PET seems to be the most reliable and stable method for this purpose, we conclude that in TLE cases it may be justified to perform MRS, which is less expensive, faster and has no radiation exposure, in combination with MRI before FDG-PET, since FDG-PET offers little additional diagnostic information if MRS and MRI indicate the same seizure focus lateralization.     

MR imaging volumetry of subcortical structures and cerebellar hemispheres in temporal lobe epilepsy

BACKGROUND AND PURPOSE: There is mounting evidence of extratemporal volume changes associated with medically refractory temporal lobe epilepsy (TLE). This MR imaging study aimed to characterize volume changes in subcortical structures and cerebellar hemispheres with respect to lateralization of the seizure focus, onset and duration of epilepsy, and frequency of generalized tonic-clonic seizures (GTCS). METHODS: Amygdalar, hippocampal, thalamic, caudate head, and cerebellar volume measurements were obtained in the preoperative MR images of 40 patients with TLE (20 right, 20 left), who underwent temporal lobe resection with good outcome, and in 20 right-handed control participants. All 3D MR images were spatially aligned and normalized before measurements were obtained. Standardized volumes and right-to-left volume ratios (VRs) were compared between control participants and right and left TLE groups. Multiple regression analyses were performed to study the effects of epilepsy onset and duration and GTCS frequency on ipsilateral-to-contralateral VRs with respect to the resected seizure focus. RESULTS: Thalamic volumes were smaller bilaterally in patients with TLE. Hippocampal volumes were smaller ipsilateral to the seizure focus, but there was no significant volume loss involving the amygdala, caudate, or cerebellum. Hippocampal and amygdalar right-to-left VRs differed significantly between right and left TLE groups and controls, whereas thalamic right-to-left VRs differed only between the TLE groups. Thalamic ipsilateral-to-contralateral VRs were correlated positively with epilepsy onset and negatively with epilepsy duration. Caudate ipsilateral-to-contralateral VRs were positively, whereas amygdalar and cerebellar VRs were negatively, correlated with GTCS frequency. CONCLUSIONS: Unilateral amygdalar and bilateral thalamic volume loss, in the absence of caudate head atrophy, is likely to reflect seizure-induced injury due to TLE. Correlations of VRs affecting the amygdala, caudate, and cerebellum with GTCS frequency may also reflect injury or a prediposition for secondary generalization. Potential effects of complex partial seizures, febrile seizures, or antiepileptic medications on subcortical structures need to be evaluated in future studies.     

Multimodal coregistration in patients with temporal lobe epilepsy--results of different imaging modalities in lateralization of the affected hemisphere in MR imaging positive and negative subgroups

BACKGROUND AND PURPOSE: In this study, intensive video electroencephalogram (EEG) monitoring, high-resolution MR imaging (MR imaging), proton MR spectroscopy ((1)H-MR spectroscopy) and single-photon emission CT (SPECT) were compared in patients with temporal lobe epilepsy (TLE) to evaluate lateralization of affected hemisphere with regard to bilateral affection and postoperative outcome. PATIENTS AND METHODS: Recall ratio of each technique for indicating the affected hemisphere was determined in 49 patients with TLE. Postoperative outcome was established by Engel classification. RESULTS: Twenty-two of 25 patients with TLE with evidence for hippocampal sclerosis in MR imaging (MR imaging-positive) were graded as unilateral by EEG findings whereas 3 were classified as bilateral. Fourteen of 24 MR imaging-negative patients were graded as unilateral by EEG and 10 as bitemporal. (1)H-MR spectroscopy indicated concordant lateralization to EEG in 82% of MR imaging-positive patients and 71% of MR imaging-negative patients and to SPECT in 84% of MR imaging-positive patients and 67% of MR imaging-negative patients with TLE. In unilateral TLE, the concordance rate of both modalities was 74% in MR imaging-positive patients and 67% in MR imaging-negative patients. Contralateral findings to EEG focus were found in 28% by (1)H-MR spectroscopy and in 27% by SPECT. Concordant findings to the operated side of different modalities revealed a clear tendency (P = .08) for a better postoperative outcome compared with bitemporal or contralateral findings. CONCLUSION: Our data demonstrate that multimodal imaging in patients with TLE improves lateralization of affected hemispheres, especially in patients without pathologic findings in MR imaging, and indicates bilateral effect, which is important to identify patients who will benefit from surgery.     

MR in temporal lobe epilepsy: analysis with pathologic confirmation.

PURPOSEWe evaluated the MR findings in patients with temporal lobe epilepsy to determine the predictive value of MR imaging in assessing patient outcome.METHODSMR studies from 186 of 274 consecutive patients who underwent temporal lobectomy for intractable epilepsy were reviewed retrospectively. Images were interpreted by an experienced neuroradiologist, who was blinded to the side of seizure activity and to pathologic findings.RESULTSMR imaging exhibited 93% sensitivity and 83% specificity in detecting hippocampal/amygdalar abnormalities (n = 121), and 97% sensitivity and 97% specificity in detecting abnormalities in the rest of the temporal lobe (n = 60). Abnormal high signal of the hippocampus on T2-weighted images had a sensitivity of 93% and specificity of 74% in predicting mesial temporal sclerosis (n = 115). The presence of hippocampal atrophy on MR correlated with the duration of seizures. Sensitivity and specificity of MR imaging in detecting temporal lobe tumors (n = 42) were 83% and 97%, respectively, based on abnormal signal and mass effect. After surgery, 63% of patients were seizure free and 28% had a significant reduction of seizure frequency at an average of 24 months (range, 12 to 78 months) after surgery. Patients with a single lesion in the anterior temporal lobe or hippocampus/amygdala had a better outcome than patients with multiple lesions (n = 22). Interrater agreement varied from 0.4 to 0.93, with best agreement for tumors or abnormal hippocampal signal on T2-weighted images.CONCLUSIONMR imaging is highly sensitive in detecting and locating abnormalities in the temporal lobe and the hippocampus/amygdala in patients with temporal lobe epilepsy. Hippocampal atrophy appears to correspond to the duration of seizure disorder.     

Inter-modality comparisons of seizure focus lateralization in complex partial seizures

Anterior temporal lobectomy offers a high chance of seizure-free outcome in patients suffering from drug-refractory complex partial seizure (CPS) originating from the temporal lobe. Other than EEG, several functional and morphologic imaging methods are used to define the spatial seizure origin. The present study was undertaken to compare the merits of fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET), magnetic resonance imaging (MRI) and single-voxel proton MR spectroscopy (MRS) for the lateralization of temporal lobe seizure foci. The clinical charts and imaging data of 43 consecutive CPS patients were reviewed. Based on surface EEG, 31 patients were classified with temporal lobe epilepsy (TLE; 25 lateralized, 6 not lateralized) and 12 with non-temporal lobe epilepsy. All were examined by FDG-PET, MRS and MRI within 6 weeks. FDG-PET and MRI were interpreted visually, while the N-acetyl-aspartate to creatine ratio was used for MRS interpretation. One FDG-PET scan was invalid due to seizure activity post injection. The MR spectra could not be evaluated in five cases bilaterally and three cases unilaterally for technical reasons. A total of 15 patients underwent anterior temporal lobectomy. All showed a beneficial postoperative outcome. When the proportions of agreement between FDG-PET (0.77), MRI (0.58) and MRS (0.56) and surface EEG in TLE cases were compared, there were no significant differences (P>0.10). However, FDG-PET showed a significantly higher agreement (0.93) than MRI (0.60; P=0.03) with the side of successful temporal lobectomy. The concordance of MRS with the side of successful temporal lobectomy was intermediate (0.75). When the results of functional and morphologic imaging were combined, no significant differences were found between the rates of agreement of FDG-PET/MRI and MRS/MRI with EEG (0.80 vs 0.68; P=0.50) and with the side of successful temporal lobectomy (0.87 vs 0.92; P=0.50) in TLE cases. However, MRS/MRI showed significantly more lateralized temporal lobe abnormalities in non-temporal lobe epilepsy cases than FDG-PET/MRI (0.90 vs. 0.17; P<0.01). Although FDG-PET seems to be the most reliable and stable method for this purpose, we conclude that in TLE cases it may be justified to perform MRS, which is less expensive, faster and has no radiation exposure, in combination with MRI before FDG-PET, since FDG-PET offers little additional diagnostic information if MRS and MRI indicate the same seizure focus lateralization.     

Sequential 123I-iododexetimide scans in temporal lobe epilepsy: comparison with neuroimaging scans (MR imaging and 18F-FDG PET imaging)

Purpose Muscarinic acetylcholine receptors (mAChRs) play an important role in the generation of seizures. Single-photon emission computed tomography (SPECT) with ¹²³I-iododexetimide (IDEX) depicts tracer uptake by mAChRs. Our aims were to: (a) determine the optimum time for interictal IDEX SPECT imaging; (b) determine the accuracy of IDEX scans in the localisation of seizure foci when compared with video EEG and MR imaging in patients with temporal lobe epilepsy (TLE); (c) characterise the distribution of IDEX binding in the temporal lobes and (d) compare IDEX SPECT and ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography (PET) in identifying seizure foci.Methods We performed sequential scans using IDEX SPECT imaging at 0, 3, 6 and 24 h in 12 consecutive patients with refractory TLE undergoing assessment for epilepsy surgery. Visual and region of interest analyses of the mesial, lateral and polar regions of the temporal lobes were used to compare IDEX SPECT, FDG PET and MR imaging in seizure onset localisation.Results The 6-h IDEX scan (92%; =0.83, p=0.003) was superior to the 0-h (36%; =0.01, p>0.05), 3-h (55%; =0.13, p>0.05) and 24-h IDEX scans in identifying the temporal lobe of seizure origin. The 6-h IDEX scan correctly predicted the temporal lobe of seizure origin in two patients who required intracranial EEG recordings to define the seizure onset. Reduced ligand binding was most marked at the temporal pole and mesial temporal structures. IDEX SPECT was superior to interictal FDG PET (75%; =0.66, p=0.023) in seizure onset localisation. MR imaging was non-localising in two patients in whom it was normal and in another patient in whom there was bilateral symmetrical hippocampal atrophy.Conclusion The 6-h IDEX SPECT scan is a viable alternative to FDG PET imaging in seizure onset localisation in TLE.     

Diffusion tensor imaging of the hippocampal formation in temporal lobe epilepsy

BACKGROUND AND PURPOSE: Diffusion tensor imaging (DTI) is a noninvasive technique that can be used to assess the integrity of cerebral tissue. The purpose of this study was to assess DTI measurements in the hippocampal formation (HF) and to investigate the role of DTI in lateralizing the seizure focus in temporal lobe epilepsy (TLE). METHODS: We evaluated 12 patients with unilateral TLE and 14 healthy subjects. We collected diffusion-weighted images along six different directions with a b value of 1000 s/mm(2), as well as an image acquired without diffusion weighting (b = 0 s/mm(2)). A 1.5-T imager was used to acquire 17 (3-mm) coronal sections covering the temporal lobes. We compared the mean diffusivity (trace D) and fractional anisotropy (FA) from symmetrical voxels by sampling the anterior HF bilaterally. We compared measurements with the EEG, high-resolution MR imaging, and clinical information. RESULTS: The patient group had significantly increased diffusivity and decreased FA in the HF ipsilateral to the seizure focus, as compared with values in the contralateral HF. When compared with healthy subjects, patients had significantly higher mean diffusivity in the ipsilateral HF; ipsilateral FA values were lower and did not reach statistical significance. Measurements in the contralateral HF did not show differences. Left-right and absolute diffusivity indices lateralized the abnormal HF in eight and five of 12 patients, respectively. CONCLUSION: Abnormal DTI measurements and the epileptogenic HF are associated in unilateral TLE. This finding may reflect hippocampal sclerosis and may aid in presurgical evaluation.     

Extent of preoperative abnormalities and focus lateralization predict postoperative normalization of contralateral 1H-magnetic resonance spectroscopy metabolite levels in patients with temporal lobe epilepsy

BACKGROUND AND PURPOSE: Magnetic resonance (MR) spectroscopy can be used to determine the side of seizure onset in patients with temporal lobe epilepsy. Some patients with abnormal MR spectroscopy findings also have contralateral abnormalities, which in some cases have been reported to normalize after temporal lobe resection. With the aim of better understanding the mechanisms underlying abnormal MR spectroscopy findings, the current study was performed to define patient features that would predict this postoperative normalization. METHODS: Fifteen patients with temporal lobe epilepsy were subjected to preoperative and postoperative 1H-MR spectroscopy investigations, and the preoperative and postoperative metabolite levels in the contralateral hippocampus and contralateral lateral temporal lobe (CLTL) were determined. RESULTS: In the CLTL, postoperative normalization was more pronounced for patients showing extensive preoperative ipsilateral and contralateral abnormalities on MR spectroscopy. A second factor that influenced the degree to which the metabolite levels changed postoperatively was the focus lateralization. Surgery tended to have a more pronounced effect on the contralateral metabolite levels in patients with a right temporal focus, whereas in patients with left temporal foci, postoperative metabolite levels were virtually unchanged. In the contralateral hippocampal region, neither preoperative abnormalities nor focus side was related to postoperative normalization. CONCLUSIONS: We have thus identified 2 different factors (widespread preoperative MR spectroscopy abnormalities and right-sided focus) that predict postoperative normalization of contralateral MR spectroscopy abnormalities. We suggest that both factors indicate a more generalized epileptic disease (ie, that the patients in whom the MR spectroscopy abnormalities normalize are recovering from a more severe impairment).     

Anterior temporal lobe white matter abnormal signal (ATLAS) as an indicator of seizure focus laterality in temporal lobe epilepsy: comparison of double inversion recovery, FLAIR and T2W MR imaging

Objectives

To investigate the diagnostic capability of anterior temporal lobe white matter abnormal signal (ATLAS) for determining seizure focus laterality in temporal lobe epilepsy (TLE) by comparing different MR sequences.

Methods

This prospective study was approved by the institutional review board and written informed consent was obtained. Three 3D sequences (double inversion recovery (DIR), fluid-attenuated inversion recovery (FLAIR) and T2-weighted imaging (T2WI)) and two 2D sequences (FLAIR and T2WI) were acquired at 3?T. Signal changes in the anterior temporal white matter of 21 normal volunteers were evaluated. ATLAS laterality was evaluated in 21 TLE patients. Agreement of independent evaluations by two neuroradiologists was assessed using ?? statistics. Differences in concordance between ATLAS laterality and clinically defined seizure focus laterality were analysed using McNemar??s test with multiple comparisons.

Results

Pre-amygdala high signals (PAHS) were detected in all volunteers only on 3D-DIR. Inter-evaluator agreement was moderate to almost perfect for each sequence. Correct diagnosis of seizure laterality was significantly more frequent on 3D-DIR than on any other sequences (P????0.031 for each evaluator).

Conclusions

The most sensitive sequence for detecting ATLAS laterality was 3D-DIR. ATLAS laterality on 3D-DIR can be a good indicator for determining seizure focus localization in TLE.

Key Points

? Magnetic resonance imaging is widely used to investigate temporal lobe epilepsy. ? Numerous MR sequences can show anterior temporal lobe white matter abnormal signal. ? ATLAS on 3D-DIR can frequently indicate seizure focus laterality in TLE. ? 3D-DIR is more sensitive about ATLAS laterality than T2WI or FLAIR.     

Ictal hyperperfusion of cerebellum and basal ganglia in temporal lobe epilepsy: SPECT subtraction with MRI coregistration.

The ictal hyperperfusion (compared with the interictal state) of the cerebellum and basal ganglia has not been investigated systematically in patients with temporal lobe epilepsy (TLE). Their ictal perfusion patterns were analyzed in relation to temporal and frontal hyperperfusion during TLE seizures using SPECT subtraction. METHODS: Thirty-three TLE patients had interictal and ictal SPECT, video-electroencephalographic (EEG) monitoring, and volumetric MRI. SPECT subtraction with MRI coregistration was performed using commercial software. The presence of ictal hyperperfusion was determined in the ipsilateral and contralateral temporal lobe, frontal lobe, cerebellum, and basal ganglia. RESULTS: All patients showed ictal hyperperfusion in the temporal lobe of seizure origin. Vermian cerebellar hyperperfusion (CH) was observed in 26 patients (78.8%) and hemispheric CH was found in 25 (75.8%). Compared with the side of the epileptogenic temporal lobe, there were 7 patients with ipsilateral hemispheric CH (28.0%), 15 with contralateral hemispheric CH (60.0%), and 3 with bilateral hemispheric CH (12.0%). CH was observed more frequently in patients with additional frontal hyperperfusion (14/15, 93.3%; 2 ipsilateral to the seizure focus, 10 contralateral, and 2 bilateral) than in patients without frontal hyperperfusion (11/18, 61.1%). Among 18 patients with temporal hyperperfusion without frontal hyperperfusion, 11 patients showed hemispheric CH (5 ipsilateral to seizure focus, 5 contralateral, 1 bilateral). Hyperperfusion in the basal ganglia (BGH) was seen in 11 of the 15 patients with temporal and frontal hyperperfusion (73.3%) and in 11 of the 18 with only temporal hyperperfusion (61.1%). In 17 patients with unilateral BGH (13 ipsilateral to the seizure focus, 4 contralateral), CH contralateral to the BGH was observed in 14 (82.5%), CH ipsilateral to the BGH was found in 2 (11.8%), and CH bilateral to the BGH was found in 1 (5.9%). CONCLUSION: During TLE seizures, hemispheric CH occurred not only in contralateral but also in ipsilateral or bilateral cerebellar hemispheres to the side of seizure origin. Although temporal lobe origin seizures associated with additional frontal hyperperfusion produced more frequent hemispheric CH, seizures showing only temporal hyperperfusion without frontal hyperperfusion could produce BGH and CH. To determine the side of hemispheric CH, the most important factor appears to be the side of BGH, not the side of seizure origin.     

Visual and quantitative analysis of interictal SPECT with technetium-99m-HMPAO in temporal lobe epilepsy

Interictal 99mTc-HMPAO SPECT images were compared to ictal EEG localization in 51 patients with intractable temporal lobe epilepsy to determine their usefulness for preoperative seizure focus localization. Both quantified temporal lobe asymmetry and blinded visual detection of temporal lobe hypoperfusion were employed. Visual analysis detected ipsilateral hypoperfusion in 18 (39%) of the 46 patients with a unilateral focus and contralateral hypoperfusion in 3. None of the five patients with bitemporal foci had unilateral hypoperfusion. The positive predictive value of unilateral temporal lobe hypoperfusion was 86% (18/21). Quantified anterior temporal lobe asymmetry, greater than a previously derived normal range, correctly identified the focus in 22 (48%) but gave the wrong side in 5, resulting in a predictive value of 81%. The degree of asymmetry correlated inversely with age of seizure onset, but not with other clinical parameters, histology, or verbal and nonverbal memory. The usefulness of interictal 99mTc-HMPAO SPECT for pre-operative seizure focus localization is limited by low sensitivity when performed with a conventional rotating gamma camera. This suggests that ictal or immediate postictal imaging may be necessary for this purpose.     

单侧颞叶癫痫病人双侧基底节区多体素MRS研究

目的 采用多体素MRS探讨单侧颞叶癫痫（TLE）病人双侧基底节区代谢物改变。方法 选取根据临床发作症状和脑电图综合诊断的左侧TLE病人10例,右侧TLE病人10例,正常志愿者10例纳入研究。所有TLE病人均进行利物浦痫性发作严重程度量表2.0（LSSS 2.0）评估,采用Simens 3.0 T超导MR设备进行多体素1H-MRS数据采集,对称性测量双侧尾状核头、豆状核和丘脑的N-乙酰天门冬氨酸（NAA）、乙酰胆碱（Cho）、肌酸（Cr）含量,计算各兴趣区NAA/Cr和Cho/Cr比值并进行统计学分析,将代谢物比值与LSSS 2.0评分进行Pearson相关分析。结果 左侧TLE组双侧丘脑NAA/Cr比值分别为1.92±0.15（左）和2.02±0.26（右）,右侧TLE组双侧丘脑NAA/Cr比值分别为2.19±0.16（左）和1.79±0.16（右）,均明显低于对照组[2.37±0.14（左）和2.36±0.10（右）,P＜0.05]。右侧TLE组,其致痫灶同侧丘脑的NAA/Cr比值较对侧丘脑要低（P＜0.05）。TLE组致痫灶同侧丘脑NAA/Cr比值与LSSS 2.0评分呈负相关（左侧 r=-0.667;右侧r=-0.643,均P＜0.05）。结论 单侧TLE病人存在双侧丘脑神经元丢失和/或功能障碍,且致痫灶同侧丘脑NAA/Cr比值与LSSS 2.0评分可以一致性反映近期痫性发作严重程度。     

Comparative analysis of MR imaging,Ictal SPECT and EEG in temporal lobe epilepsy: a prospective IAEA multi-center study

Background and purpose MR imaging, ictal single-photon emission CT (SPECT) and ictal EEG play important roles in the presurgical localization of epileptic foci. This multi-center study was established to investigate whether the complementary role of perfusion SPECT, MRI and EEG for presurgical localization of temporal lobe epilepsy could be confirmed in a prospective setting involving centers from India, Thailand, Italy and Argentina. Methods We studied 74 patients who underwent interictal and ictal EEG, interictal and ictal SPECT and MRI before surgery of the temporal lobe. In all but three patients, histology was reported. The clinical outcome was assessed using Engel’s classification. Sensitivity values of all imaging modalities were calculated, and the add-on value of SPECT was assessed. Results Outcome (Engel’s classification) in 74 patients was class I, 89%; class II, 7%; class III, 3%; and IV, 1%. Regarding the localization of seizure origin, sensitivity was 84% for ictal SPECT, 70% for ictal EEG, 86% for MRI, 55% for interictal SPECT and 40% for interictal EEG. Add-on value of ictal SPECT was shown by its ability to correctly localize 17/22 (77%) of the seizure foci missed by ictal EEG and 8/10 (80%) of the seizure foci not detected by MRI. Conclusions This prospective multi-center trial, involving centers from different parts of the world, confirms that ictal perfusion SPECT is an effective diagnostic modality for correctly identifying seizure origin in temporal lobe epilepsy, providing complementary information to ictal EEG and MRI. Part of this work was presented at the 2005 SNM meeting in Toronto, Canada.     

Evidence of neuronal injury outside the medial temporal lobe in temporal lobe epilepsy: N-acetylaspartate concentration reductions detected with multisection proton MR spectroscopic imaging--initial experience

PURPOSE: To determine whether magnetic resonance (MR) spectroscopic imaging reveals metabolic changes, especially decreased N-acetylaspartate (NAA) concentrations outside the medial temporal lobe in patients with mesial temporal lobe epilepsy (TLE), consistent with neuropathologic findings of extratemporal neuronal impairment. MATERIALS AND METHODS: Eleven patients with mesial TLE and 13 control subjects were examined with multisection MR spectroscopic imaging. Three MR spectroscopic imaging sections were acquired. Thirteen brain regions in each hemisphere and the midbrain were analyzed in each patient, and the NAA to creatine-phosphocreatine (Cr) plus choline-containing compounds (Ch) (NAA/[Cr + Ch]) ratios were determined. In addition, hemispheric and whole-brain values were calculated and statistically analyzed. RESULTS: The NAA/(Cr + Ch) ratio in the ipsilateral hippocampus was significantly reduced, compared with that in the contralateral hippocampus (P <.002) and compared with that in control subjects (P <.03), confirming findings in previous studies. In patients, whole-brain NAA/(Cr + Ch) ratio outside the hippocampus was significantly lower than that in control subjects (P <.002). For the ipsilateral hemisphere in patients, NAA/(Cr + Ch) ratio was significantly lower than that in control subjects (P <.0002). Comparisons between individual brain regions revealed trends toward lower NAA/(Cr + Ch) ratios in many areas of the ipsilateral and, to a lesser extent, the contralateral hemisphere outside the hippocampus and temporal lobe, suggesting diffuse impairment. CONCLUSION: Results suggest that repeated seizure activity damages neurons outside of the seizure focus.     

Fractional anisotropy asymmetry and the side of seizure origin for partial onset-temporal lobe epilepsy

This paper presents a fractional anisotropy asymmetry (FAA) method to detect the asymmetry of white matter (WM) integrity and its correlation with the side of seizure origin for partial onset temporal lobe epilepsy (TLE) using diffusion tensor image (DTI). In this study, FAA analysis is applied to 30 patients of partial TLE (15 left, 15 right) and 14 matched normal controls. Specifically, after registering all the images with the JHU-DTI-MNI template the average FA value of each FA skeleton section is calculated using the tract-based spatial statistics (TBSS) method. Then, FAA is calculated to quantify the WM diffusivity asymmetry of the corresponding region-pairs between the left and right hemispheres. Using FAA the regional asymmetry contributing significantly to the group differences of controls and left/right TLE, as well as the left and right TLE, is identified. As a comparison, the ROI-based average FA values for WM and corresponding FAAs are also calculated. TBSS-based analysis reflects the average of local maximal FA values along the white matter skeleton sections, and ROI-based analysis shows the average of WM FA values within each anatomical region. The FAA statistical results indicated that the FA values of anatomical region-pairs are asymmetric in the ipsilateral hemisphere with seizure origin against the contralateral hemisphere. Particularly, FAA values within the temporal lobe (superior, middle, and inferior temporal WM) are significantly different between the left and right TLE patients, consistently found from both analysis methods. The study suggests that FAA values can be potentially used to identify the seizures of origin of TLE and to help understand the relationship between fiber tracts with the side of seizure origin of TLE.     

Uncinate fasciculus fiber tracking in mesial temporal lobe epilepsy. Initial findings

In temporal lobe epilepsy (TLE) due to hippocampal sclerosis (HS), ictal discharge spread to the frontal and insulo-perisylvian cortex is commonly observed. The implication of white matter pathways in this propagation has not been investigated. We compared diffusion tensor imaging (DTI) measurements along the uncinate fasciculus (UF), a major tract connecting the frontal and temporal lobes, in patients and controls. Ten right-handed patients referred for intractable TLE due to a right HS were investigated on a 1.5-T MR scanner including a DTI sequence. All patients had interictal fluorodeoxyglucose PET showing an ipsilateral temporal hypometabolism associated with insular and frontal or perisylvian hypometabolism. The controls consisted of ten right-handed healthy subjects. UF fiber tracking was performed, and its fractional anisotropy (FA) values were compared between patients and controls, separately for the right and left UF. The left-minus-right FA UF asymmetry index was computed to test for intergroup differences. Asymmetries were found in the control group with right-greater-than-left FA. This asymmetrical pattern was lost in the patient group. Right FA values were lower in patients with right HS versus controls. Although preliminary, these findings may be related to the preferential pathway of seizure spread from the mesial temporal lobe to frontal and insulo-perisylvian areas.     

5-HT 1A receptors are reduced in temporal lobe epilepsy after partial-volume correction.

Preclinical studies suggest that serotonin 1A receptors (5-HT 1A) play a role in temporal lobe epilepsy (TLE). Previous PET studies reported decreased 5-HT 1A binding ipsilateral to epileptic foci but did not correct for the partial-volume effect (PVE) due to structural atrophy. METHODS: We used PET with 18F-trans-4-fluoro-N-2-[4-(2-methoxyphenyl)piperazin-1-yl]ethyl-N-(2-pyridyl)cyclohexanecarboxamide (18F-FCWAY), a 5-HT 1A receptor antagonist, to study 22 patients with TLE and 10 control subjects. In patients, 18F-FDG scans also were performed. An automated MR-based partial-volume correction (PVC) algorithm was applied. Psychiatric symptoms were assessed with the Beck Depression Inventory Scale. RESULTS: Before PVC, significant (uncorrected P < 0.05) reductions of 18F-FCWAY binding potential (BP) were detected in both mesial and lateral temporal structures, mainly ipsilateral to the seizure focus, in the insula, and in the raphe. Group differences were maximal in ipsilateral mesial temporal regions (corrected P < 0.05). After PVC, differences in mesial, but not lateral, temporal structures and in the insula remained highly significant (corrected P < 0.05). Significant (uncorrected P < 0.05) BP reductions were also detected in TLE patients with normal MR images (n = 6), in mesial temporal structures. After PVC, asymmetries in BP remained significantly greater than for glucose metabolism in hippocampus and parahippocampus. There was a significant inverse relation between the Beck Depression score and the ipsilateral hippocampal BP, both before and after PVC. CONCLUSION: Our study shows that in TLE patients, reductions of 5-HT 1A receptor binding in mesial temporal structures and insula are still significant after PVC. In contrast, partial-volume effects may be an important contributor to 5-HT 1A receptor-binding reductions in lateral temporal lobe. Reduction of 5-HT 1A receptors in the ipsilateral hippocampus may contribute to depressive symptoms in TLE patients.