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.     

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.     

Electrical source imaging for presurgical focus localization in epilepsy patients with normal MRI

Purpose: Patients with magnetic resonance (MR)–negative focal epilepsy (MRN‐E) have less favorable surgical outcomes (between 40% and 70%) compared to those in whom an MRI lesion guides the site of surgical intervention (60–90%). Patients with extratemporal MRN‐E have the worst outcome (around 50% chance of seizure freedom). We studied whether electroencephalography (EEG) source imaging (ESI) of interictal epileptic activity can contribute to the identification of the epileptic focus in patients with normal MRI. Methods: We carried out ESI in 10 operated patients with nonlesional MRI and a postsurgical follow‐up of at least 1 year. Five of the 10 patients had extratemporal lobe epilepsy. Evaluation comprised surface and intracranial EEG monitoring of ictal and interictal events, structural MRI, [¹⁸F]fluorodeoxyglucose positron emission tomography (FDG‐PET), ictal and interictal perfusion single photon emission computed tomography (SPECT) scans. Eight of the 10 patients also underwent intracranial monitoring. Results: ESI correctly localized the epileptic focus within the resection margins in 8 of 10 patients, 9 of whom experienced favorable postsurgical outcomes. Discussion: The results highlight the diagnostic value of ESI and encourage broadening its application to patients with MRN‐E. If the surface EEG contains fairly localized spikes, ESI contributes to the presurgical decision process.     

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.     

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.     

Ictal/postictal SPECT in the pre-surgical localisation of complex partial seizures.

Single photon emission computed tomography (SPECT) used in conjunction with HM-PAO (Ceretec-Amersham International) was used to image regional cerebral blood flow (rCBF) in 28 patients with medically intractable complex partial seizures during or soon after a seizure, and interictally. Changes from interictal rCBF were seen in 26/28 (93%) patients. The main findings were; 1) During the seizure--hyperperfusion of the whole temporal lobe; 2) Up to 2m postically--hyperperfusion of the hippocampus with hypoperfusion of lateral temporal structures; 3) From 2-15m postically--hypoperfusion of the whole temporal lobe. When compared with EEG and MRI data, correct localisation to one temporal lobe was obtained in 23 patients. In one further patient bilateral temporal foci, and in a further two patients frontal foci, were correctly identified. There were no disagreements between EEG and SPECT localisation. Temporal lobe surgery was successful (by the criterion of at least 90% reduction in seizure frequency) in all but one of the 23 patients operated on. It is concluded that ictal/postictal SPECT is a reliable technique for the presurgical localisation of complex partial seizures. The data indicate a likely sequence of changes in rCBF during and after complex partial seizures of temporal lobe origin.     

Regional relationships between focal hypofixation images in 123I-IMP single photon emission computed tomography and epileptic EEG foci in interictal periods in patients with partial epilepsy.

Single photon emission computed tomographic (SPECT) brain scans with N-isopropyl-(iodine-123)-p-iodoamphetamine were performed in interictal periods in 40 patients with partial epilepsies and normal X-ray CT findings, and the regional relationships between the SPECT abnormalities and interictal epileptic EEG foci were studied. Twenty-six patients (65%) had abnormal SPECT images consisting of one or more focal hypofixation images, i.e., zones of decreased regional cerebral blood flow, while the remaining 14 patients showed normal images. Nineteen (73%) of the 26 patients showed complete or partial regional agreement between the abnormal SPECT findings and the interictal epileptic EEG foci determined from EEGs recorded repeatedly during their clinical course, while the regional relationships with the EEG foci determined from the single EEG recorded just after the SPECT scans or a short interval after the scans showed a lower rate of agreement (13 of 21 patients, 61.9%). These results confirm the utility of SPECT scans in the regional diagnosis of epileptic foci.     

Temporal lobe epilepsy with bilateral seizure origin studied by [18F]FDG-positron emission tomography

Nine patients who underwent presurgical evaluation because of medically refractory temporal lobe epilepsy (TLE) showed either unilateral, although alternating in side, or bilateral simultaneous seizure onsets in both temporal lobes (TL). EEG recordings with semi-invasive foramen ovale electrodes revealed in seven patients a predominance of seizure onset in one TL of between 50% and 88%. In two patients the majority of seizures originated simultaneously in both TL. In four patients a unilateral selective amygdalohippocampectomy resulted in a good to excellent seizure outcome without noteworthy memory deficits and confirmed the preoperative lateralization of the primary epileptogenic focus by interictal ¹⁸F-fluorodeoxyglucose positron emission tomography (PET). Five patients were rejected from surgery due to strong bilaterality of their epilepsy and/or divergent presurgical findings. PET contributed to the decision of whether surgery should be performed: all patients who underwent surgery had a unilateral TL hypometabolism which was concordant with the findings of other tests. Patients in whom surgery was denied had either bilateral temporal hypometabolism or the PET findings were discordant with other results obtained during the presurgical evaluation.     

Relationship of nonlinear analysis,MRI and SPECT in the lateralization of temporal lobe epilepsy

OBJECTIVES: The purpose of this study was to investigate the correlation of lateralization by nonlinear analysis, magnetic resonance imaging (MRI) and interictal single-photon emission computed tomography (SPECT) in patients with temporal lobe epilepsy. METHODS: Twenty-three patients (7 males, 16 females) were examined by MRI, interictal SPECT and EEG. Nonlinear dynamic properties of neuronal networks were estimated by calculating correlation dimensions on interictal EEG signals and corresponding surrogate data. Lateralization was detected based on the criteria introduced in this study. Concordance rates of the results among the three methods were compared. RESULTS: Epileptogenic foci were shown in the temporal areas in 21 patients using the nonlinear method (8 left, 2 right, 11 both), while 20 patients showed abnormalities in temporal lobes on MR images (13 left, 5 right, 2 both). Low cerebral blood flows of the temporal lobes were detected in all patients (11 left, 8 right, 4 both). Completely concordant lateralization was observed in 8 patients (35%) for the nonlinear method and MRI, in 9 patients (39%) for the nonlinear method and SPECT, and in 10 patients (43%) for MRI and SPECT. There were no significant differences among the concordance rates for these different methods. CONCLUSIONS: Our results revealed that correlation dimension is useful for differentiating dynamic properties of neuronal networks in the interictal state, and can provide informative data for localizing epileptogenic foci in epileptic patients. Therefore, the present nonlinear method is recommended for use with patients during presurgical evaluation.     

Ictal and interictal 99mTc-HMPAO-SPECT studies in temporal lobe epilepsy with unilateral EEG focus]

Ictal and interictal SPECT measurements using 99mTc-HMPAO are helpful in localising an epileptic focus. 24 patients (12 women and 12 men; mean age 30 years) suffering from temporal lobe epilepsies with unilateral EEG foci were examined. In all patients a presurgical evaluation including sphenoidal and foramen oval electrodes was carried out. The analysis of SPECT measurement was done visually and semi-quantitatively, comparing the data with findings in healthy persons (10 women and 10 men; mean age 24 years). The etiology of the epilepsy was confirmed by histological investigation in 16 cases, and by CT and MRI in 8 cases. The findings were gliosis in 6 cases, astrocytoma in 3 cases, cysts in 4 cases, and angioma in 3 cases. In 8 cases no pathological findings could be detected. In 46% of cases interictal SPECTs exhibited a focal hypoperfusion corresponding with the EEG-focus. In ictal SPECTs this could be found in 75% of cases. In all 10 patients without morphological findings or with gliosis (proved by histological investigations) a hyperperfusion coincident with the EEG-focus appeared in ictal SPECTs.     

68例额叶癫痫的外科治疗与长期疗效随访

目的 总结额叶癫痫的术前评估特征,观察远期手术疗效.方法 分析68例额叶癫痫患者的术前评估结果,总结症状学特征、MRI、发作闻期 SPECT、头皮video-EEG、颅内电极EEG检查的定位价值;应用Engel标准进行术后效果分级,随访2-6年,观察术后的远期疗效.结果 不同评估方法口可提供准确定位信息的比例分别为:症状学特征38%,MRI40%,发作间期SPECT 28%,头皮video-EEG44%,颅内电极EEG81%.最常见的病理改变为皮质发育不良44%(30/68).Engel I级的60%(41/68),II级的12%(8/68),Ⅲ级的10%(7/68),Ⅳ～V级的18%(12/68).癫痫灶定位局限于额叶的病例疗效相对好于M时累及其他脑叶的病例(P<0.05).出现短期并发症10例,长期并发症2例.结论 应用术前综合评估方法,有助于准确定位癫痫灶的位置和范围,手术切除癫痫灶疗效稳定.     

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.     

Correlation of ictal EEG and SPECT studies in patients of intractable epilepsy with normal MRI

Identification of the epileptic focus is the most important requirement for a successful surgical outcome in intractable epilepsy. Patients with normal MRI on high-resolution imaging pose a significant challenge in this regard. We tried to identify the epileptic focus using interictal / ictal SPECT and ictal EEG patterns in 14 patients with normal MRI. Rhythmic ictal onset activity helped to identify a single focus in 10 patients (71.43%). Inter ictal SPECT detected a focus corresponding to ictal EEG in 6 out of 10 patients (60%) in whom the test was performed. Ictal SPECT done in 5 patients correctly identified the focus in all patients (100%). Our data indicate that it is possible to obtain localization in patients with normal MRI using a combination of ictal EEG patterns and an ictal SPECT study.     

Postictal SPECT in Epileptic Versus Nonepileptic Seizures

Despite advances in video-electroencephalogram (EEG) technology, in many patients distinguishing epileptic seizures from nonepileptic seizures (NES) remains a challenge. Reliable methods to make this distinction are needed. In a pilot study, we performed postictal and interictal single photon emission computed tomography (SPECT) in 22 patients undergoing video-EEG monitoring who had altered responsiveness during an episode. Eleven had seizures, defined as episodes associated with EEG seizure patterns or postictal prolactin (PRL) elevations greater than 1.5 times the highest interictal baseline PRL; 11 had NES. Among the 11 seizures, postictal SPECT was abnormal in seven (regions of hypoperfusion in six and hyperperfusion in one) and normal in four. In six cases (55%), the interictal and postictal SPECT changed. Among the 11 NES cases, postictal SPECT was abnormal in three cases (all hypoperfusion abnormalities) and normal in eight cases. In no case did the interictal and postictal SPECT change. This small sample revealed a trend toward greater hypometabolism (postictal versus interictal) on SPECT for epileptic seizures compared to NES (p < 0.12). There were postictal SPECT changes in two of five seizures unassociated with postictal PRL elevation. Prolactin was elevated in two cases unassociated with change on SPECT. Comparision of postictal to interictal SPECT may help distinguish epileptic seizures from NES. Results from SPECT may also help identify epileptic seizures unassociated with PRL elevation.     

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.     

Correlation of SPECT with pathology and seizure outcome in children undergoing epilepsy surgery

SPECT can be used to image regional cerebral blood flow (rCBF) and has been shown to help localize the seizure focus in partial epilepsies as part of the presurgical evaluation. Few studies have explored the possible relation between preoperative SPECT and underlying pathology, or any relation to postsurgical outcome. In this study preoperative ictal and interictal rCBF in relation to the histopathological diagnosis and outcome in a series of 35 children (24 females, 11 males; mean age 9.6 years, age range 11 months to 18 years) who had undergone resective surgery for epilepsy were retrospectively evaluated. A correlation between ictal hyperperfusion and the underlying responsible pathology was shown, with a consistent ictal increase in perfusion in developmental pathologies and Rasmussen's encephalitis, and consistent interictal hypoperfusion in hippocampal sclerosis (HS). No rCBF study parameter appeared to relate to outcome but in the group with HS the best outcome was seen in those with localizing ictal rCBF. The varied group of pathologies from hemispherectomy had excellent outcome but the SPECT findings had little to contribute over the abnormalities detected on MRI. In conclusion, rCBF studies remain a useful presurgical investigation in children with partial epilepsy, especially where HS, cortical dysplasia, or inflammatory disease are the underlying pathology. However, rCBF studies add little to the investigation of children with seizures secondary to benign tumours or cerebral infarcts, or where hemispherectomy is the likely preferred surgical option.     

Visualizing prolonged hyperperfusion in post-stroke epilepsy using postictal subtraction SPECT

Diagnosis of post-stroke epilepsy is often challenging because of a low incidence of epileptiform abnormalities on electroencephalography (EEG). Hence, this study evaluated whether postictal subtraction single-photon emission computed tomography (SPECT) could visualize epileptic activity and act as a diagnostic modality in post-stroke epilepsy. Fifty post-stroke epilepsy patients, who had undergone Tc-99m-ECD SPECT twice (postictal and interictal), were enrolled. The postictal hyperperfusion area was identified by subtraction (postictal–interictal) SPECT and classified into two distribution types: superficial or deep-seated. Laterality and distribution of postictal hyperperfusion on subtraction SPECT were compared with stroke lesions, seizure symptoms, and epileptiform EEG findings. Forty-three of the 50 patients (86%) had hyperperfusion on subtraction SPECT and 26 (52%) had epileptiform EEG findings. Subtraction SPECT showed prolonged postictal hyperperfusion despite the relatively long interval between seizure end and postictal SPECT (median: 19.1 h, range: 2.2–112.5 h). The laterality of the hyperperfusion area had a high concordance rate with the laterality of stroke lesions (97.7%), seizure symptoms (91.9%), and epileptiform EEG findings (100%). Scalp EEG identified epileptiform activity more frequently in superficial type of SPECT, but less frequently in deep-seated type (both, P = 0.03). Postictal SPECT can be complementary to scalp EEG in endorsing the diagnosis and location of post-stroke epilepsy.     

Interictal HM-PAO SPECT: a routine investigation in patients with medically intractable complex partial seizures?

Single photon emission computed tomography (SPECT) is increasingly being used as an adjunctive technique in the localisation of epileptogenic foci prior to surgery. As yet, few studies have been undertaken to establish the clinical associations of areas of reduced cerebral perfusion. Sixty-three consecutive patients (15 male, 48 female; median age 30 years, range 14-57 years) with medically intractable complex partial seizures (median/month 8, range 1-36) were investigated as outpatients. All had normal high resolution computerised X-ray tomography (CT) of brain. Twenty-seven (47%) exhibited significant perfusion defects on SPECT scanning with a rotating gamma camera system using Tc-99 HM-PAO. There were no significant differences between patients with normal and abnormal scans in terms of age at scanning or at onset of epilepsy or number of seizures. Patients with perfusion defects did, however, have longer median histories of epilepsy than those with normal scans (normal: 10 years, abnormal: 22 years; P = 0.01). Patients with abnormal scans were no more likely to have suffered febrile convulsions in early childhood. The correlation of abnormal SPECT scans with routine surface EEG recordings was poor with only 41% of cases showing clear agreement between the site of hypoperfusion and focal epileptic activity. It is not yet possible to predict clinically those patients who will exhibit perfusion defects on interictal TC-99 HM-PAO SPECT scanning.     

Reexamination of 123I-IMP-SPECT at interictal stages in adult partial epilepsy

123I-IMP-SPECT scans at the interictal stages in 13 epileptic patients with normal X-ray CT findings were reexamined at intervals of 1.9 +/- 0.8 years. Interictal scalp EEGs were recorded a few hours after each SPECT scan. All of the SPECT abnormalities indicated focal hypofixation images of 123I-IMP, i.e. zones of a decreased rCBF reflecting a functional inactivation. Among 11 patients with the SPECT abnormalities in the first SPECTs, eight cases had the complete or partial regional reproduction of the abnormalities in the second SPECTs. As changes in the SPECT findings, an alteration from the abnormal SPECT images to normal images (normalization), the reverse change, the enlargement and reduction of hypofixation sites were seen. Also the EEG foci had various changes (right and left regional changes, etc.). Because of these SPECT and EEG changes, the regional relationship between the SPECT abnormalities and EEG foci altered in 7 patients (a change from disagreement to agreement, etc.). The high reproduction rate of SPECT abnormalities appears to increase the reliability or utility of SPECT scans for a regional diagnosis of epileptic foci. The present SPECT changes, especially the normalization or the severse change, suggest that the interictal epileptic focus may have a functional fluctuation. In addition, the causes of regional disagreement between the SPECT abnormalities and EEG foci were discussed on the basis of the present SPECT and EEG changes.     

Ictal and Interictal Activity in Partial Epilepsy Recorded with Multichannel Magnetoelectroencephalography: Correlation of Electroencephalography/Electrocorticography, Magnetic Resonance Imaging, Single Photon Emission Computed Tomography, and Positron Emission Tomography Findings

Ictal and interictal epileptic activity was recorded for the first time by multichannel magnetoencephalography (MEG) in three patients with partial epilepsy. Pre- and intra-operative localization of the epileptogenic region was compared. The interictal epileptic activity was localized at the same region of the temporal or frontal lobe as the ictal activity. Main zones of ictal activity were shown to evolve from the tissue at the centers of interictal activity. Pre- and intra-operative electrocorticography (ECoG) as well as postoperative outcome confirmed localization in the temporal and frontal lobe. Results also correlated with findings from scalp EEG, interictal and ictal single photon emission computed tomography (SPECT), positron emission tomography (PET), and magnetic resonance imaging (MRI). Combined multichannel MEG/EEG recording permitted dipole localization of interictal and ictal activity.