Pre-surgical evaluation and surgical outcome of 41 patients with non-lesional neocortical epilepsy.

Pre-surgical evaluation and the surgical treatment of non-lesional neocortical epilepsy is one of the most challenging areas in epilepsy surgery. The aim of this study was to evaluate the surgical outcome and the diagnostic role of ictal scalp electroencephalography (EEG), interictal (18)F-fluorodeoxyglucose-positron emission tomography (FDG-PET), and ictal technetium-99m hexamethylpropyleneamine oxime single photon emission tomography ( (99m)Tc-HMPAO SPECT). In 41 non-lesional neocortical epilepsy patients (16 frontal lobe epilepsy, 11 neocortical temporal lobe epilepsy, seven occipital lobe epilepsy, four parietal lobe epilepsy, and three with multifocal onset) who underwent surgical treatment between December 1994 and July 1998, we evaluated the surgical outcome with a follow-up of at least 1 year. The localizing and lateralizing values of ictal scalp EEG, interictal FDG-PET, and ictal SPECT were evaluated in those patients with good surgical outcome. Ictal scalp EEG had the highest diagnostic sensitivity in the localization of epileptogenic foci (69.7% vs. 42.9% for FDG-PET and 33.3% for ictal SPECT; P= 0.027). However, no significant difference was found in the lateralization of the epileptogenic hemisphere among the three modalities (78.8% for ictal scalp EEG, 57.2% for FDG-PET, and 55.5% for ictal SPECT; P= 0.102). During a mean follow-up of 2.77 +/- 1.12 years, 33 (80.5%) showed good surgical outcome (seizure free or seizure reduction >90%), including 16 (39.0%) seizure free patients. Ictal scalp EEG was the most useful diagnostic tool in the localization of epileptogenic foci. Interictal FDG-PET and ictal SPECT were found to be useful as complementary and, sometimes, independent modalities. Many patients with non-lesional neocortical epilepsy would benefit from surgical treatment.     

Periictal SPECT localization verified by simultaneous intracranial EEG

PURPOSE: We investigated whether blood-flow changes measured by ictal or immediate postictal single photon emission computed tomography (SPECT) reflect with accuracy the actual location of ictal discharge as measured by simultaneous intracranial EEG. In addition, we evaluated the reliability of ictal SPECT obtained with implanted electrodes by comparing results with those of ictal SPECT performed during scalp EEG monitoring in selected patients. METHODS: Eleven patients with intractable partial epilepsy who had both ictal and interictal SPECT scans during invasive EEG monitoring were studied. We analyzed perfusion differences based on registration, normalization, and subtraction of periictal and interictal SPECT images. SPECT results were interpreted in relation to location and evolution of ictal EEG change, as reflected by simultaneous intracranial EEG. In five patients, we also compared ictal SPECT results that were obtained during both scalp and intracranial EEG monitoring. RESULTS: In 10 of 11 patients, localized increases or decreases in blood flow or both were identified in regions of ongoing or prior seizure discharge, respectively, at the time of SPECT brain perfusion. In one patient, SPECT localization could not be verified by the available electrode array. CONCLUSIONS: Localization of ictal discharge during or before SPECT injection accurately determines increase or decrease in perfusion, respectively, and both are of equal validity in reflecting the region of epileptic discharge. SPECT perfusion changes can be reliably obtained during intracranial monitoring.     

Interictal PET and ictal subtraction SPECT: Sensitivity in the detection of seizure foci in patients with medically intractable epilepsy

Purpose: Interictal positron emission tomography (PET) and ictal subtraction single photon emission computed tomography (SPECT) of the brain have been shown to be valuable tests in the presurgical evaluation of epilepsy. To determine the relative utility of these methods in the localization of seizure foci, we compared interictal PET and ictal subtraction SPECT to subdural and depth electrode recordings in patients with medically intractable epilepsy. Methods: Between 2003 and 2009, clinical information on all patients at our institution undergoing intracranial electroencephalography (EEG) monitoring was charted in a prospectively recorded database. Patients who underwent preoperative interictal PET and ictal subtraction SPECT were selected from this database. Patient characteristics and the findings on preoperative interictal PET and ictal subtraction SPECT were analyzed. Sensitivity of detection of seizure foci for each modality, as compared to intracranial EEG monitoring, was calculated. Key Findings: Fifty‐three patients underwent intracranial EEG monitoring with preoperative interictal PET and ictal subtraction SPECT scans. The average patient age was 32.7 years (median 32 years, range 1–60 years). Twenty‐seven patients had findings of reduced metabolism on interictal PET scan, whereas all 53 patients studied demonstrated a region of relative hyperperfusion on ictal subtraction SPECT suggestive of an epileptogenic zone. Intracranial EEG monitoring identified a single seizure focus in 45 patients, with 39 eventually undergoing resective surgery. Of the 45 patients in whom a seizure focus was localized, PET scan identified the same region in 25 cases (56% sensitivity) and SPECT in 39 cases (87% sensitivity). Intracranial EEG was concordant with at least one study in 41 cases (91%) and both studies in 23 cases (51%). In 16 (80%) of 20 cases where PET did not correlate with intracranial EEG, the SPECT study was concordant. Conversely, PET and intracranial EEG were concordant in two (33%) of the six cases where the SPECT did not demonstrate the seizure focus outlined by intracranial EEG. Thirty‐three patients had surgical resection and >2 years of follow‐up, and 21 of these (64%) had Engel class 1 outcome. No significant effect of imaging concordance on seizure outcome was seen. Significance: Interictal PET and ictal subtraction SPECT studies can provide important information in the preoperative evaluation of medically intractable epilepsy. Of the two studies, ictal subtraction SPECT appears to be the more sensitive. When both studies are used together, however, they can provide complementary information.     

Good surgical outcome in discordant ictal EEG-MRI unilateral mesial temporal sclerosis patients

Purpose: Video electroencephalography (vEEG) monitoring of patients with unilateral mesial temporal sclerosis (uMTS) may show concordant or discordant seizure onset in relation to magnetic resonance imaging (MRI) evidence of MTS. Contralateral seizure usually leads to an indication of invasive monitoring. Contralateral seizure onset on invasive monitoring may contraindicate surgery. We evaluated long-term outcome after anteromesial temporal lobectomy (AMTL) in a consecutive series of uMTS patients with concordant and discordant vEEG findings, uniformly submitted to AMTL on the MRI evidence of MTS side without invasive monitoring.
Methods: We compared surgical outcome of all uMTS patients undergoing vEEG monitoring between January 1999 and April 2005 in our service. Discordant cases were defined by at least one seizure onset contralateral to the MRI evidence of MTS. Good surgical outcome was considered as Engel's class I. We also evaluated ictal SPECT concordance to ictal EEG and surgical outcome.
Results: Fifty-four patients had concordant (C) and 22 had discordant (D) scalp EEG and MRI. Surgical outcome was similar in both groups (C = 74% versus D = 86%). Duration of follow-up was comparable in both groups: C = 56.1 ± 20.7 months versus D = 59.8 ± 21.2 months (p = 0.83, nonsignificant). Discordant single-photon emission computed tomography (SPECT) results did not influence surgical outcome.
Discussion: Surgical outcome was not influenced by contralateral vEEG seizure onset or contralateral increased flow on ictal SPECT. Although vEEG monitoring should still be performed in these patients, to rule out psychogenic seizures and extratemporal seizure onset, a potentially risky procedure such as invasive monitoring may not only not be indicated in this patient population, but may also lead to patients erroneously being denied surgery.     

无创性定位手段在颞叶内侧癫(癎)患者癫(癎)灶定位中的价值

目的 评价多种无创性定位手段在颞叶内侧癫(癎)患者术前癫(癎)灶定位中的可靠性.方法 选择2002年5月至2005年5月间在我院行前颞叶内侧切除,随访1年以上,预后为Engle I级的40例患者,回顾性地总结这组病例发作间期和发作期脑电图、发作症状、头颅MRI、发作问期SPECT所提供的定侧定位信息,分析其在癫疴灶定位中的价值.结果 (1)发作间期颞前尖波:出现单侧独立尖波者37例(92.5%),其中35例(94.6%)与癫(癎)灶侧别相符;(2)发作期脑电图:32例获取了发作期脑电图,26例(81.2%)的发作期脑电图可提供定侧信息,其中25例(96.2%)与癫(癎)灶的侧别相符;(3)发作症状:23例(57.5%)患者的发作症状可以提供癫(癎)灶侧别信息,其中19例(82.6%)提供的侧别信息与癫(癎)灶侧别一致;(4)头颅MRI:38例(95.0%)头颅MRI提示一侧海马及颞叶的信号或结构异常,其中37例(97.4%)与癫(癎)灶侧别相符;(5)发作间期SPECT:23例患者行同位素检查,22例(95.7%)可提供癫(癎)灶侧别信息,其中18例(81.8%)与癫(癎)灶侧别相符.结论 颞叶内侧癫(癎)术前无创性定位定侧方法中,提供定侧信息比较敏感的方法依次为SPECT、MRI、发作问期脑电图、发作期脑电图和发作症状,而定侧信息可靠性的高低依次为头颅MRI、发作期脑电图、发作间期脑电图、发作症状和SPECT.     

Repeated ictal SPECT in partial epilepsy patients: SISCOM analysis

Purpose: Ictal single‐photon emission computerized tomography (SPECT) is often nonlocalized in patients with partial epilepsy. We repeated ictal SPECT in patients with partial epilepsy whose first ictal SPECT was nonlocalized. We also performed subtraction ictal SPECT coregistered to magnetic resonance imaging (MRI) (SISCOM) to test the localizability of ictal SPECT. Methods: We recruited 69 patients with partial epilepsy (33 male and 36 female, mean plus or minus standard deviation age 29.5 ± 12.2 years), who had a repeated ictal SPECT. Ictal‐interictal SPECT subtractions were performed, and the subtracted SPECTs were coregistered with their brain MRI studies. SISCOM results were considered to be localizing when the results were concordant with the final location of the epileptic focus, as determined by the presurgical evaluation. We compared seizure duration, tracer injection time, interictal and ictal scalp electroencephalography (EEG) patterns, presence and time of secondary generalization, and epilepsy classification between the localized and nonlocalized SISCOM groups. Key Findings: The SISCOM results of the second ictal SPECT were localized in 43 (62.3%) patients and nonlocalized in 26 (37.7%) patients. In the second ictal SPECT, the radiotracer injection time was significantly shorter in the localized group (25.1 ± 8.9 s), as compared to the nonlocalized group (49.2 ± 55.8 s) (p = 0.008). Furthermore, the radiotracer injection time of the second ictal SPECT was significantly shorter than the first ictal SPECT, only in the localized group (36.8 ± 23.8 s in the first and 25.1 ± 8.9 s in the second ictal SPECT in the localized group, p = 0.004). The percent injection time ([(tracer injection time−seizure onset time)/total seizure duration] × 100%) in the second SPECT was significantly shorter in the localized group, as compared to the nonlocalized group (37.9 ± 23.0% in the localized group and 72.3 ± 46.2% in the nonlocalized group, p < 0.001). The localized ictal EEG patterns at the time of injection were more frequent in the localized SISCOM group. The secondary generalization of seizures at the time of injection was more frequent in nonlocalized groups. Significance: Repeated ictal SPECT with SISCOM analysis is helpful for localizing an epileptic focus in patients with partial epilepsy who have a nonlocalized first ictal SPECT. The most important factor for increasing the localizability of repeated ictal SPECT is early injection time and a localizing ictal EEG pattern at the time of radiotracer injection.     

Association of Combined MRI, Interictal EEG, and Ictal EEG Results with Outcome and Pathology After Temporal Lobectomy

Summary: Purpose: Magnetic resonance imaging, interictal scalp EEG, and ictal scalp EEG each have been shown to localize the primaly epileptic region in most patients with mesial-basal temporal lobe epilepsy (MBTLE), but the association of surgical outcome and pathology with each combination of these test results is not known. Methods: We reviewed the MRI, interictal scalp EEG, and ictal scalp EEG results of 90 consecutive patients with MBTLE. Twelve patients were excluded from the analysis because inconclusive bitemporal intracranial EEG results precluded anterior temporal lobectomy (ATL); none had concordant MRI and interictal scalp EEG results. We compared all combinations of presurgical MRI, interictal EEG, and ictal EEG results to seizure outcome and tissue pathology in the 78 patients who underwent an ATL. Results: Forty-eight (61%) patients had concordant lateral-ized MRI and interictal EEG temporal lobe abnormalities, with no discordant ictal EEG results; 77% of these patients were seizure-free after ATL. Concordance of MRI and interictal EEG abnormalities correlated with seizure cessation (p < 0.05), compared to all combinations with discordant or nonlateralizing MRI and interictal EEG results. Mesial temporal sclerosis (MTS) was confirmed pathologically in about 80% of both groups (p = 0.5). Outcome in patients with concordant MRI and ictal EEG with nonlateralizing interictal EEG was significantly worse than combinations with concordant MRI and interictal EEG (p < 0.02). Conclusions: Compared to other combinations of test results, concordance of MRI and interictal EEG is most closely associated with surgical outcome in MBTLE. However, most selected patients have pathologic confirmation of MTS regardless of test results or outcome. This information may be useful for planning the presurgical evaluation of patients with medically intractable MBTLE.     

Comparative utility of technetium-99m hexamethylpropylenamine oxime single photon emission computed tomography (SPECT) with anatomic neuroimaging and electroencephalography (EEG) in childhood intractable epilepsy

Intractable epilepsies pose a therapeutic challenge. Precise localization of the epileptic focus is imperative before planning surgical intervention. Functional imaging is an important component of presurgical work-up. Positron emission tomography is unavailable in developing countries; hence, the need to evaluate the available imaging modality, single photon emission computed tomography (SPECT), was felt. We investigated 61 children with intractable epilepsy, identified by predefined criteria, by performing electroencephalography (EEG), magnetic resonance imaging (MRI), computed tomography (CT), and ictal and interictal SPECT. The localizing value of ictal and interictal SPECT imaging for epileptic foci was correlated with clinical, electrophysiologic, and anatomic neuroimaging data. An ictal SPECT was obtained in 9, and interictal SPECT was performed in all (61). Ictal SPECT was localizing in 8 of 9 (88.8%). Interictal SPECT was localizing in a significantly higher proportion of patients (47.54%) than either the scalp EEG (16.39%) (P = .0003) or CT scan (21.56%) (P = .0046). Our data demonstrated that interictal and ictal SPECT identified more focal changes in children with intractable epilepsy than interictal EEG, CT, and probably MRI. The definitive proof of the SPECT-based findings being epileptogenic foci awaits correlation with intraoperative monitoring and postoperative follow-up.     

Surgical outcome and prognostic factors of cryptogenic neocortical epilepsy

Surgical treatment of cryptogenic neocortical epilepsy is challenging. The aim of this study was to evaluate surgical outcomes and to identify possible prognostic factors including the results of various diagnostic tools. Eighty-nine patients with neocortical epilepsy with normal magnetic resonance imaging (35 patients with frontal lobe epilepsy, 31 with neocortical temporal lobe epilepsy, 11 with occipital lobe epilepsy, 11 with parietal lobe epilepsy, and 1 with multifocal epilepsy) underwent invasive study and focal surgical resection. Patients were observed for at least 2 years after surgery. The localizing values of interictal electroencephalogram (EEG), ictal scalp EEG, interictal 18F-fluorodeoxyglucose positron emission tomography (FDG-PET), and subtraction ictal single-photon emission computed tomography were evaluated. Seventy-one patients (80.0%) had a good surgical outcome (Engel class 1-3); 42 patients were seizure free. Diagnostic sensitivities of interictal EEG, ictal scalp EEG, FDG-PET, and subtraction ictal single-photon emission computed tomography were 37.1%, 70.8%, 44.3%, and 41.1%, respectively. Localization by FDG-PET and interictal EEG was correlated with a seizure-free outcome. The localizing value of FDG-PET was greatest in neocortical temporal lobe epilepsy. The focalization of ictal onset and also ictal onset frequency in invasive studies were not related to surgical outcome. Concordance with two or more presurgical evaluations was significantly related to a seizure-free outcome.     

Challenges in the surgical treatment of epilepsy patients with cortical dysplasia

Cortical dysplasia (CD) is the most common malformation of cortical development in epilepsy surgery patients. Patients with mild Palmini type I CD represent about 50% of the surgical cases, and these lesions tend to occur most often in the temporal lobe, often associated with hippocampal sclerosis. By comparison, patients with severe type II CD present at younger ages, often with multilobar extratemporal lesions, and more aggressive seizures. The presurgical evaluation in CD patients can be challenging, as no single test is 100% accurate. Based on retrospective cohort studies, the accuracy of investigations are: interictal scalp electroencephalography (EEG), 50%; ictal scalp EEG, 65%; magnetic resonance imaging (MRI), 66%; fluorodeoxyglucose–positron emission tomography (FDG-PET), 81%; and ictal single photon emission computed tomography (SPECT), 57%. Intracranial electrodes are used in about 50% of patients with CD. Contemporary series report that 62% of patients with CD are seizure free after resective neurosurgery, with higher rates for complete (77%) compared with incomplete (20%) removal of the lesion. Morbidity (<3%) and mortality (0.2%) are low for patients with CD undergoing epilepsy neurosurgery. Future challenges include the noninvasive identification of patients with CD with 100% accuracy, evaluation of long-term outcomes in surgical patients, and devising new treatments based on a better understanding of the neurobiology leading to seizures in CD tissue.     

视频脑电图与发作期SPECT对痫灶定位的对比研究

目的 探讨视频脑电图(VEEG)、发作期SPECT在术前痫灶定位中的作用.方法 回顾性对比分析48例难治性癫痫患者术前所行长程VEEG与发作期SPECT定位的情况,比较两者定位的一致性.结果 发作期SPECT定位阳性率为94%,VEEG为96%.两者完全一致占46%,部分一致占29%,完全不一致占25%.阳性率及定侧率差异无统计学意义(P＞0.05),局灶定位差异有统计学意义(P＜0.01).随访结果显示48例患者中Engel Ⅰ级27例,Ⅱ级10例,Ⅲ级8例,Ⅳ级3例;其中EngelⅠ～Ⅱ级的37例中33例来自两者定位一致的患者.结论 发作期SPECT与VEEG检查有较高的一致性,两者联合应用优势互补,可提高定位准确性,获得良好的手术疗效.     

Parietal lobe epilepsy: the semiology, yield of diagnostic workup, and surgical outcome

PURPOSE: To characterize the clinical features, the prognostic value, and diagnostic sensitivities of various presurgical evaluations and the surgical outcomes in parietal lobe epilepsy (PLE), we describe 40 patients who were diagnosed as having PLE, including 27 surgically treated patients. METHODS: The diagnosis was established by means of a standard presurgical evaluation, including magnetic resonance imaging (MRI), fluorodeoxyglucose-positron emission tomography (FDG-PET), ictal single-photon emission tomography (SPECT), and scalp video-electroencephalography (EEG) monitoring, with additional intracranial EEG monitoring in selected cases. RESULTS: Among the 40 patients, 27 experienced at least one type of aura. The most common auras were somatosensory (13 patients), followed by affective, vertiginous, and visual auras. The patients had diverse manifestations. Eighteen patients showed simple motor seizure, followed by automotor seizure, and dialeptic seizure. Two patients manifested generalized tonic-clonic seizures only, and 19 patients experienced more than one type of seizure. The surgical outcome was favorable in 22 of 26 patients including 14 who were seizure free. Patients with localized MRI abnormality had a higher probability to be seizure free, with marginal significance (p = 0.062), whereas other diagnostic modalities failed to predict the surgical outcome. In the seizure-free group, localization sensitivity was 64.3% by MRI, 50% by PET, 45.5% by ictal SPECT, and 35.7% by ictal EEG. The concordance rate of the various diagnostic modalities was higher in the seizure-free group than in the non-seizure-free group, although it did not reach statistical significance. CONCLUSIONS: Seizures, in the case of PLE, can manifest themselves in a wider variety of ways than was previously thought. Surgical outcome was favorable in most of the patients. MRI abnormality and concordance of different diagnostic modalities were associated with high seizure-free rate.     

Usefulness of Unilateral Interictal Sharp Waves of Temporal Lobe Origin in Prolonged Video-EEG Monitoring Studies

The value of EEG interictal epileptiform activity in predicting location of the seizure focus remains controversial. In 64 patients, scalp video-EEG monitoring studies showed one or two ipsilateral interictal foci in the temporal lobe. The site of these interictal foci correlated with location of the seizure focus recorded during prolonged video-electrocorticography (ECoG) with use of subdural grids placed under the mesiobasal temporal region and over the lateral temporal convexity. Our findings suggest that unilateral anterotemporal interictal foci can accurately predict location of seizure onset. This is also true in patients with two ipsilateral temporal interictal foci, provided that the dominant focus is localized in anterotemporal regions. We believe that in such patients invasive recordings are not warranted, but we caution against sole use of interictal epileptiform criteria for localization of the seizure focus. Correlation with clinical information, ictal EEG, neuropsychometric, and neu-roimaging studies is required before performance of epilepsy surgery.     

A Comparison of Magnetoencephalography, MRI, and V-EEG in Patients Evaluated for Epilepsy Surgery

PURPOSE: To determine the efficacy and relative contribution of several diagnostic methods [ictal and interictal scalp and intracranial EEG, magnetic resonance imaging (MRI), and magnetoencephalography (MEG)] in identifying the epileptogenic zone for resection. METHODS: This was a prospective study using a masked comparison-to-criterion standard. Fifty-eight consecutive patients with refractory partial epilepsy from two university comprehensive epilepsy programs were studied. Patients who were evaluated for and underwent epilepsy surgery were recruited. The main outcome measure was the efficacy of each diagnostic method to identify the resected epileptogenic zone, when referenced to surgical outcome. RESULTS: MEG (52%) was second only to ictal intracranial V-EEG in predicting the epileptogenic zone for the entire group of patients who had an excellent surgical outcome (seizure free or rare seizure). In a subanalysis, for patients who had temporal lobe surgery, this same relation was seen (MEG, 57%, ictal intracranial V-EEG, 62%). With extratemporal resection, ictal (81%) and interictal (75%) intracranial EEG were superior to MEG (44%) in predicting the surgery site in those patients with an excellent outcome. Finally, for all patients who had a good surgical outcome, MEG (52%) was better than ictal (33%) or interictal (45%) scalp VEEG in predicting the site of surgery. CONCLUSIONS: These results indicate that MEG is a very promising diagnostic method and raise the possibility that it may obviate the need for invasive EEG in some cases or reduce the length of scalp EEG evaluation in others.     

Subtraction SPECT coregistered to MRI in focal malformations of cortical development: localization of the epileptogenic zone in epilepsy surgery candidates

PURPOSE: To determine the extent to which periictal subtraction single-photon emission computed tomography (SPECT) may improve detection and definition of the epileptogenic zone in patients with focal malformations of cortical development (MCDs). METHODS: Subtraction SPECT coregistered to magnetic resonance (MR) images (SISCOM) were constructed for 22 consecutive patients with focal MCDs who underwent periictal SPECT injection (18 ictal and four postictal). In the 17 patients who had epilepsy surgery, concordance between the site of SISCOM localization and site of surgical resection was determined by coregistration of SISCOM images with postoperative MRIs. RESULTS: SISCOM images were localizing in 19 (86%) patients, including eight of the 10 with nonlocalizing MRI. Concordance of SISCOM localization was 91% with MRI localization, 93% with scalp ictal EEG localization, and 100% with intracranial EEG localization. Eight patients whose SISCOM localization was concordant with the surgical resection site had lower postoperative seizure frequency scores (SFSs; p = 0.04) and greater postoperative improvement in SFSs (p = 0.05) than the nine patients whose SISCOM was either nonconcordant or nonlocalizing. On multiple regression analysis, a model combining SISCOM concordance with surgical resection site and extent of MRI lesion resection was predictive of postoperative SFS (R2 = 0.47; p = 0.03). CONCLUSIONS: Periictal subtraction SPECT using the SISCOM technique provides useful information for seizure localization in patients with focal MCDs, even when MRI is nonlocalizing.     

Ictal brain imaging in presurgical evaluation of patients with medically intractable complex partial seizures

At the Indiana University Medical Center, 99 patients with medically intractable complex partial seizures (MI-CPS) had presurgical evaluation with subsequent anterior temporal lobectomy. The majority of the patients had single photon emission tomography (SPECT) performed interictally as well as during an actual epileptic seizure (ictal scan). Decreased regional cerebral perfusion (rCP) was seen in 54/94 (57%) of the interictal scans corresponding to the eventual site of the surgery. However, ictal scans provided a higher yield; increased rCP in the temporal lobe during an actual seizure was observed in 60/82 (73%) concordant to the side of surgery. SPECT is a useful, noninvasive method of localizing the epilepti-form focus in patients with MI-CPS considered for resective surgery. Both interictal and ictal SPECT need to be performed; combined interictal hypo-perfusion and ictal hyperperfusion in the same focal area are unique to epileptogenic lesions. Ictal SPECT studies can be performed in the majority of patients during the period of continuous video/EEG monitoring with only a little additional effort. Combining the results of functional brain imaging (interictal and ictal SPECT, PET) with clinical semiology of seizures, surface and sphenoidal EEG, magnetic resonance imaging and other non-invasive tests, anterior temporal lobectomy can be recommended in approximately two-thirds of the patients without resorting to potentially dangerous intracranial EEG monitoring.     

Ictal SPECT is useful in localizing the epileptogenic zone in infants with cortical dysplasia

Aims. To assess the localizing value of ictal SPECT in very young epilepsy surgery candidates when cerebral haemodynamic responses are known to be immature. Methods. We retrospectively studied 13 infants with intractable focal epilepsy caused by focal cortical dysplasia (FCD). Completeness of resection of the (1) ictal SPECT hyperperfusion zone and (2) cerebral cortex with prominent ictal and interictal abnormalities on intracranial EEG (ECoG or long‐term invasive monitoring) and the MRI lesion, when present, were correlated with postoperative seizure outcome. Results. All five patients with complete resection of the ictal SPECT hyperperfusion zone were seizure‐free compared to only one of eight patients with incomplete or no excision of hyperperfusion zones (p=0.00843). Similar results were noted for the MRI/iEEG‐defined epileptogenic region; five of six patients with complete removal were seizure‐free, whereas only one of seven incompletely resected patients was seizure‐free (p=0.02914). All four patients who underwent complete resection of both regions were seizure‐free compared to none of the six with incomplete resection (p=0.01179). Conclusion. Despite age‐related differences in cerebral perfusion, ictal SPECT provides useful localization data in infants with FCD. Complete resection of the hyperperfused regions is a strong predictor of favourable outcome. The added information may alleviate the need for invasive EEG evaluations in some patients.     

Comparison of modern diagnostic methods in children with intractable focal epilepsy

The basic aim of neuroimaging in children with intractable focal epilepsy is stablishing localization of epileptogenic zone. In this study 34 children (age 11-17 years) with intractable focal epilepsy were examined including: clinical history, physical examination, EEG, CT, MR, 99mTc-HMPAO SPECT. The hypoperfused region in interictal SPECT was concordant with clinical seizure characteristics in 22 children, with EEG in 13, with MR with 13 children. The localization of hyperperfused region in ictal SPECT was concordant with the clinical seizure characteristics in 9 from 10 examined children, with EEG in 7 and with MR in 8. The diagnostic value of estimation of the localization of epileptogenic zone in interictal SPECT (63 per cent) was comparable with the results of EEG (56 per cent) and MR (59 per cent), but ictal SPECT offers more information (100 per cent). In conclusion, performing both ictal and interictal SPECT studies may provide data about both seizure origin and its relationship with structurally abnormal regions of the brain.     

Ictal and interictal ECD-SPECT for focus localization in epilepsy

Forty-one ECD (Technetium-99m-ethyl cysteinate dimer) SPECT investigations were undertaken in the course of a presurgical diagnostic work-up in 23 patients with pharmacoresistant focal epilepsy. In 21 patients, both an ictal and interictal SPECT were conducted. In the patients receiving ictal SPECT the tracer was injected between 7 and 30 s after the seizure onset. Of the interictal SPECTs 17 of 23 showed focal hypoperfusion which was consistent in 17 cases (74%) with the area of the electrophysiological focus (EF) and 6 patients had a normal interictal SPECT. Of the ictal SPECTs 18 of 21 (86%) showed regional hyperperfusion, 18 of them in the same location as the EF. Ictal SPECT showed a hypoperfusion similar to that in interictal SPECT in another 3 patients. In these cases seizure duration was short (28–54 s), so that the tracer reached the brain postictally. Our results show that ictal ECD-SPECT is an effective method for demonstrating an epileptogenic focus. Possible reasons for false-negative ictal SPECT results are discussed.     

Accuracy of ictal SPECT in mesial temporal lobe epilepsy with bilateral interictal spikes

OBJECTIVE: In mesial temporal lobe epilepsy (MTLE), the rate of correct seizure lateralization of ictal semiology and ictal EEG is better for patients with unilateral interictal spikes (UIS) than for patients with bilateral interictal spikes (BIS), possibly due to rapid seizure propagation patterns associated with bilateral epileptogenesis. In this study, the authors investigated if ictal SPECT is a reliable diagnostic test for both UIS and BIS patients. METHODS: Video-EEG recording was used as the gold standard to examine the accuracy of ictal SPECT and its relationship with interictal and ictal EEG. Ninety-three consecutive patients with MTLE associated with hippocampal sclerosis were included in the analysis. Ictal SPECT was considered accurate if two blinded observers independently lateralized the scan correctly. RESULTS: Ictal SPECT correctly lateralized 75 (80.6%) of 93 scans. The rate of correct seizure lateralization was 87.6% for the UIS group and only 55.0% for the BIS group (p = 0.0027). In the EEG epochs, 66.7% of BIS patients vs 43.4% of UIS patients had nonlateralized ictal EEG (p < 0.001). CONCLUSION: The authors conclude that the accuracy of ictal SPECT is worse for MTLE patients with BIS than for those with UIS. The role of ictal SPECT in presurgical evaluation of patients with BIS must be reviewed.