Automatic and remote controlled ictal SPECT injection for seizure focus localization by use of a commercial contrast agent application pump

PURPOSE: In the presurgical evaluation of patients with partial epilepsy, the ictal single photon emission computed tomography (SPECT) is a useful noninvasive diagnostic tool for seizure focus localization. To achieve optimal SPECT scan quality, ictal tracer injection should be carried out as quickly as possible after the seizure onset and under highest safety conditions possible. Compared to the commonly used manual injection, an automatic administration of the radioactive tracer may provide higher quality standards for this procedure. In this study, therefore, we retrospectively analyzed efficiency and safety of an automatic injection system for ictal SPECT tracer application. METHODS: Over a 31-month period, 26 patients underwent ictal SPECT by use of an automatic remote-controlled injection pump originally designed for CT-contrast agent application. Various factors were reviewed, including latency of ictal injection, radiation safety parameters, and ictal seizure onset localizing value. RESULTS: Times between seizure onset and tracer injection ranged between 3 and 48 s. In 21 of 26 patients ictal SPECT supported the localization of the epileptogenic focus in the course of the presurgical evaluation. In all cases ictal SPECT tracer injection was performed with a high degree of safety to patients and staff. CONCLUSIONS: Ictal SPECT by use of a remote-controlled CT-contrast agent injection system provides a high scan quality and is a safe and confirmatory presurgical evaluation technique in the epilepsy-monitoring unit.     

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.     

Ictal fear auras after selective amygdalohippocampectomy: the use of ictal SPECT and scalp EEG in the presurgical reevaluation

The perception of fear aura in complex partial seizures is linked to epileptic discharges within mesial temporal lobe structures. Although selective amygdalohippocampectomy often leads to favorable seizure control, persistence of fear auras after surgery can hamper quality of life significantly. We describe two patients with persistent fear auras after selective amygdalohippocampectomy who had to be reevaluated for a second operative procedure. In one patient, ictal SPECT revealed focal hyperperfusion within the left temporal pole. In the other patient, localization of the focus was possible with ictal scalp EEG, which revealed closely time-related focal theta activity in the right frontotemporal electrodes. Both patients underwent a second surgery leading to complete remission. The persistence of fear auras after selective amygdalohippocampectomy provides an example of involvement of a complex neuronal network in the generation of this emotional state during mesiotemporal lobe seizures. Ictal SPECT or ictal scalp EEG may be valuable in identifying the involved areas and in guiding the surgeon to render these patients seizure free.     

Regional Cerebral Blood Flow During Temporal Lobe Seizures Associated with Ictal Vomiting: An Ictal SPECT Study in Two Patients

PURPOSE: Ictal vomiting represents a rare clinical manifestation during seizures originating from the temporal lobes of the nondominant hemisphere. The precise anatomic structures responsible for generation of ictal vomiting remain to be clarified. Ictal single photon emission computed tomography (SPECT), which allows one to visualize the three-dimensional dynamic changes of regional cerebral blood flow (rCBF) associated with the ongoing epileptic activity, should be useful to study the brain areas activated during ictal vomiting. METHODS: We performed ictal Tc-HMPAO SPECT scans in two patients with mesial temporal lobe epilepsy (MTLE) whose seizures were characterized by ictal retching and vomiting. MTLE was documented by typical clinical seizure semiology, interictal and ictal EEG findings, hippocampal atrophy on magnetic resonance imaging (MRI) scan, and a seizure-free outcome after selective amydalohippocampectomy. In both patients, seizures originated in the nondominant temporal lobe. We obtained accurate anatomic reference of rCBF changes visible on SPECT by a special coregistration technique of MRI and SPECT. We used ictal SPECT studies in 10 patients with MTLE who had seizures without ictal vomiting as controls. RESULTS: In the two patients with ictal vomiting, we found a significant hyperperfusion of the nondominant temporal lobe (inferior, medial, and lateral superior) and of the occipital region on ictal SPECT. In patients without ictal vomiting, on the contrary, these brain regions never were hyperperfused simultaneously. CONCLUSIONS: Ictal SPECT provides further evidence that activation of a complex cortical network, including the medial and lateral superior aspects of the temporal lobe, and maybe the occipital lobes, is responsible for the generation of ictal vomiting.     

Anterior cingulate gyrus epilepsy: the role of ictal rCBF SPECT in seizure localization

PURPOSE: The goal of this report is to demonstrate the utility of ictal brain single photon emission tomography (SPECT) in a 39-year-old man with complex partial seizures arising from the anterior cingulate gyrus. Seizures originating from the anterior cingulate gyrus are difficult to localize because they have variable ictal semiology, are usually brief, and have rapid cortical propagation. METHODS: Clinical neurologic examination, electroencephalography, extended video-electroencephalography with scalp and sphenoidal electrodes, magnetic resonance imaging, computed tomography, and ictal brain SPECT with Tc-99m HMPAO were performed to identify the seizure focus. The patient's regional cerebral blood flow (rCBF) findings were compared with those of eight normal controls, and changes in rCBF were assessed by comparing the patient's ictal scan with those of normal controls at rest by using statistical parametric mapping (SPM). RESULTS: Clinical and neurologic evaluations failed to demonstrate the epileptogenic focus. Ictal rCBF brain SPECT showed a focal region of hyperperfusion in the anterior cingulate gyrus. By using SPM, the ictal blood flow increase in the right anterior cingulate gyrus (x, y, z, -6, 42, 24 mm) was found to be statistically significant when compared with normal controls (z score, 4.88, p < 0.001). Subdural EEG recordings with intracranial electrodes positioned over this location confirmed that the cingulate gyrus was the origin of the seizures, and surgical resection resulted in >90% seizure reduction. CONCLUSIONS: We concluded that ictal brain SPECT localization in conjunction with subdural electrode confirmation is a useful test in the presurgical evaluation of difficult to localize cingulate epilepsy.     

Ictal SPECT in supplementary motor area seizures

Abstract

Objectives: We used ictal single photon emission computed tomography (SPECT) to clarify the propagation pathways of epileptic discharges in patients with supplementary motor area (SMA) seizure.

Methods: In four patients (four males, age range, 18–27 years) with SMA seizures, SPECT studies by radioisotope 99mTc-ECD were performed as a preoperative evaluation. Two of the patients remained seizure-free after complete resection of the focal cortical dysplasia on magnetic resonance (MR) images including epileptic foci. In the other two patients, MR images were normal, but subdural electrode monitoring allowed for verifying the ictal onset in the left SMA. After partial resection of the SMA including epileptic foci, these patients experienced a significant (>90%) reduction of seizure frequency. Regional cerebral blood flow (rCBF) measurements obtained under ictal and interictal conditions were compared on a voxel-by-voxel basis by means of the SPM99 paired t-test option (uncorrected p<0.001).

Results: Significant increases in rCBF under ictal conditions were identified in the bilateral anterior cingulate cortex (ACC), the globus pallidus ipsilateral to epileptic foci and the contralateral cerebellar hemisphere. The right ACC included a cluster with a submaximum in the right primary sensorimotor area.

Discussion: In patients with SMA seizures, the hyperperfusion areas of ictal SPECT did not localize within the SMA but spread to the adjacent cortex such as the ACC and sensorimotor cortex ipsilateral to epileptic foci. Additionally, the epileptic discharges propagated to the remote areas such as the globus pallidus and cerebellum. We caution that ictal SPECT localization in patients with SMA seizures is not always concordant to epileptic focus but reveals already spread seizure activities.     

Ictal perfusion patterns associated with single MRI-visible focal dysplastic lesions: implications for the noninvasive delineation of the epileptogenic zone

BACKGROUND: Invasive electroencephalogram (EEG) studies are often considered necessary to localize the epileptogenic zone in partial epilepsies associated with focal dysplastic lesions (FDL). Our aim was to evaluate the relationships between subtraction ictal SPECT coregistered with magnetic resonance imaging (MRI) (SISCOM) hyperperfusion clusters and MRI-visible FDL, and to establish a preliminary algorithm for a noninvasive presurgical evaluation protocol for MRI-visible FDLs in patients with refractory epilepsy. METHODS: Fifteen consecutive patients with refractory partial epilepsy and a single MRI-visible FDL underwent a noninvasive presurgical evaluation including SISCOM. Each hyperperfusion cluster was visually analyzed, automatically quantitated, and its distance form the lesion as outlined on the MRI was measured. In patients who underwent surgery, the volumes of resected brain tissue containing the FDL, the SISCOM hyperperfusion cluster, and surrounding regions were assessed on postoperative MRI and correlated with surgical outcome. RESULTS: Fourteen of the 15 patients (93%) showed SISCOM hyperperfusion overlapping with the FDL. The FDL was detected only after reevaluation of the MRI guided by the ictal SPECT in 7 of the 15 patients (47%). Four distinct hyperperfusion patterns were observed, representing different degrees of seizure propagation. Nine patients have been operated on. Five have been seizure-free since surgery and one since a reoperation. The degree of resection of the MRI-visible FDL was the major determinant of surgical outcome. Full resection of the SISCOM hyperperfusion cluster was not required to render a patient seizure-free. CONCLUSION: Detailed analysis of SISCOM hyperperfusion patterns is a promising tool to detect subtle FDL on MRI and to establish the epileptic nature of these lesions noninvasively. Overlap between the SISCOM hyperperfusion cluster and MRI-visible FDL in a noninvasive presurgical evaluation with concordant data may suffice to proceed to epilepsy surgery aimed at removing the MRI-visible FDL and the part of the hyperperfusion cluster within and immediately surrounding the FDL.     

Temporal Lobe Epilepsy Subtypes: Differential Patterns of Cerebral Perfusion on Ictal SPECT

Summary: Purpose : We studied cerebral perfusion patterns in the various subtypes of TLE, as determined by pathology and good outcome after temporal lobectomy (as confirmation of temporal origin).
Methods : We studied clinical features and ictal technetium ^99m hexamethyl-propyleneamineoxime (99mTc-HM-PAO) single-photon emission-computed tomography (SPECT) in four subgroups of patients with intractable temporal lobe epilepsy (TLE) treated with surgery: hippocampal sclerosis (group 1, n = 10), foreign-tissue lesion in mesial temporal lobe (group 2, n = 8), foreign-tissue lesion in lateral temporal lobe (group 3, n = 7), and normal temporal lobe tissue with good surgical outcome (group 4, n = 5).
Results : No major clinical differences in auras, complex partial seizures or postictal states were identified among the groups. Ictal SPECT showed distinct patterns of cerebral perfusion in these subtypes of TLE. In groups 1 and 2, hyperperfusion was seen in the ipsilateral mesial and lateral temporal regions. In group 3, hyperperfusion was seen bilaterally in the temporal lobes with predominant changes in the region of the lesion. Hyperperfusion was restricted to the ipsilateral anteromesial temporal region in group 4. Ipsilateral temporal hyperperfusion in mesial onset seizures can be explained by known anatomic projections between mesial structures and ipsilateral temporal neocortex. Bilateral temporal hyperperfusion in lateral onset seizures can be explained by the presence of anterior commissural connections between lateral temporal neocortex and the contralateral amygdala.
Conclusions : We conclude that the perfusion patterns seen on ictal SPECT are helpful for subclassification of temporal lobe seizures, whereas clinical features are relatively unhelpful. These perfusion patterns provide an insight into preferential pathways of seizure propagation in the subtypes of TLE.     

Ictal brain hyperperfusion contralateral to seizure onset: the SPECT mirror image

PURPOSE: Ictal single-photon emission computed tomography (SPECT) may help localize the seizure-onset zone (SOZ) by detecting changes in regional cerebral blood flow induced by epileptic discharges. This imaging method also reveals hyperperfusions in areas of seizure propagation, including the hemisphere contralateral to the SOZ. We have studied the occurrence, the topography, and the clinical value of such contralateral ictal hyperperfusion areas (HPAs). METHODS: We examined data from presurgical evaluations of 36 consecutive patients with pharmacoresistant partial epilepsy of various localizations. Ictal and interictal SPECT examinations were made with 99mTc-ECD, and the scans were processed for coregistration, normalization, subtraction, and merging with MRI images. RESULTS: Contralateral HPAs were observed in 72% of the patients: 50% of mesiotemporal epilepsy cases with hippocampal sclerosis, 85.7% of the other mesiotemporal epilepsies, 85.7% of neocortical lateral temporal epilepsies, and 87.5% of extratemporal epilepsies. Contralateral HPAs were usually symmetrical to the SOZ, forming a mirror image, observed in 57.1% of the patients. They could be slightly asymmetrical in mesiotemporal epilepsies, perhaps because of the particular anatomic pathways linking temporal lobes. In neocortical epilepsies, they were located in the cortex homotopic to the SOZ. CONCLUSIONS: We show that the symmetrical nature of the mirror image usually does not disturb SPECT interpretation. It can confirm the location of the SOZ (11 patients) and even occasionally improve the precision of its definition (nine patients) by restraining several potential SOZ-related HPAs to a single one or by permitting a restricted localization of the SOZ in a large HPA.     

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 SPECT in Nonlesional Extratemporal Epilepsy

Summary:  Purpose: Ictal single-photon emission computed tomography (SPECT) may be a reliable indicator of the ictal onset zone in patients with intractable partial epilepsy who are being considered for epilepsy surgery. The rationale for the illustrated case report is to evaluate the use of an innovation in SPECT imaging in a patient with nonlesional extratemporal epilepsy.
Methods: We investigated the presurgical evaluation and operative outcome in a patient with intractable partial epilepsy. The ictal semiology indicated a "hypermotor" seizure with bipedal automatism. The electroclinical correlation and magnetic resonance imaging (MRI) did not suggest the appropriate localization of the epileptogenic zone. A subtraction periictal SPECT coregistered to MRI (SISCOM) was peformed.
Results: SISCOM revealed a region of localized hyperperfusion in the right supplementary sensorimotor area. Chronic intracranial EEG monitoring confirmed the relationship between the localized SISCOM alteration and the ictal onset zone. The patient was rendered seizure free after surgical treatment.
Conclusions: SISCOM may be used to identify potential candidates for surgical treatment of nonlesional extratemporal epilepsy. Periictal imaging may also alter the strategy for intracranial EEG recordings and focal cortical resection.     

Stratifying differences on ictal/interictal subtraction SPECT images

PURPOSE: Subtraction of interictal from ictal single-photon emission computed tomography (SPECT) yields numerous foci that encompass a range of pixel values scattered in the brain. This preliminary study evaluated the significance of this range of values. METHODS: Subtraction images were obtained by registering, normalizing, and subtracting interictal from ictal SPECT for 13 patients. Pixel values of the resulting foci were divided into two groups: group I with 75-100% and group II with 50-75% of the maximal pixel value. Locations of these foci were determined, and concordance with surgical outcomes and scalp and invasive EEG findings was evaluated. RESULTS: In 10 of 13 cases, group I foci showed good concordance with ictal scalp EEG. In addition, group I foci corresponded well to invasive EEG findings in nine of 10 cases. Group I foci had bilateral distributions in seven of 13 cases. In 10 of 13 cases, group I foci corresponded well to regions of surgical resection. Of these 10 patients, nine showed good concordance with scalp EEG, eight showed good invasive EEG concordance, and eight were seizure free after resection. Conversely, group II foci had good concordance with ictal scalp EEG in only five of 13 cases, and invasive EEG findings, in only five of 10 cases. Group II foci had bilateral distributions in 10 of 13 cases. All 10 cases underwent unilateral surgical resections, and all had good surgical outcomes. In six of 13 cases, group II foci showed concordance with surgical sites. Of these six foci, four had poor concordance with scalp EEG, one had poor concordance with invasive EEG, and five had good surgical outcomes. Sensitivity and specificity for seizure localization of Group I foci were 40% and 88% respectively while sensitivity and specificity of Group II foci were 20% and 79% respectively. CONCLUSIONS: Our data demonstrate that foci with 75-100% of maximal pixel values show good concordance with seizure foci, whereas foci of 50-75% may not. Therefore stratifying ictal/interictal differences may improve the specificity and localizing value of subtraction SPECT.     

Superiority of HMPAO ictal SPECT to ECD ictal SPECT in localizing the epileptogenic zone

PURPOSE: We examined diagnostic performances of Tc-99m hexamethylpropylene amine oxime (HMPAO) and Tc-99m electron capture detection (ECD) ictal single-photon emission computed tomography (SPECT) to localize the epileptogenic zones in mesial temporal lobe epilepsy (TLE) and neocortical epilepsy (NE). METHODS: Epileptogenic zones were identified by invasive EEG or surgical outcome. Ictal SPECT was performed with stabilized Tc-99m HMPAO (TLE, 17; NE, 23) and with Tc-99m ECD (TLE, 7; NE, 7). Single-blind visual interpretation was used to localize the epileptogenic zones. Asymmetric index was calculated. Subtraction ictal SPECT was coregistered to a magnetic resonance imaging (MRI) template. RESULTS: In TLE, the sensitivity of Tc-99m HMPAO SPECT was 82% (14 of 17) and that of Tc-99m ECD SPECT was 71% (five of seven). The asymmetric index (AI; 25 +/- 10) of Tc-99m HMPAO SPECT was larger (p = 0.05) than the AI (13 +/- 13) of Tc-99m ECD SPECT in patients with TLE. In NE, the sensitivity of Tc-99m HMPAO SPECT was 70% (16 of 23), but that of Tc-99m ECD SPECT was 29% (two of seven). The AI (15 +/- 10) of Tc-99m HMPAO SPECT was significantly larger (p = 0.02) than the AI (4.8 +/- 6) of Tc-99m ECD SPECT in patients with NE. Subtraction ictal SPECT coregistered to MRI supported the visual assessment. CONCLUSIONS: We concluded that the sensitivity of Tc-99m ECD ictal SPECT is similar to that of Tc-99m HMPAO ictal SPECT in TLE; however, ictal hyperperfusion was higher with the Tc-99m HMPAO SPECT. In patients with NE, Tc-99m HMPAO ictal SPECT also was superior to Tc-99m ECD ictal SPECT in sensitivity and degree of hyperperfusion.     

Ictal SPECT in clinical perisylvian syndrome

In the congenital bilateral perisylvian syndrome, pseudobulbar symptoms, cognitive deficits and cortical malformations in the perisylvian region are typical features. We report two initially magnetic resonance imaging (MRI) negative patients from our epilepsy surgery program that shared the same seizure and ictal SPECT characteristics suggesting seizure onset localized in the perisylvian region. In one patient, reevaluation revealed perisylvian cortical malformation on MRI while in the other patient MRI was normal. In these patients, subtraction ictal SPECT coregistered with MRI (SISCOM) proved useful together with clinical data in diagnosing the patients with mild forms of perisylvian syndrome.     

The usefulness of subtraction ictal SPECT coregistered to MRI in single- and dual-headed SPECT cameras in partial epilepsy

PURPOSE: To prove the clinical usefulness of SISCOM and compare SISCOM images derived from single- and dual-headed single-photon computed tomography (SPECT) cameras for localization of partial epileptic seizures. METHODS: We retrospectively studied 38 partial epilepsy patients, using subtraction SPECT coregistered to magnetic resonance imaging (MRI; SISCOM). SPECT imaging of the first 15 patients was performed by single-headed camera, and the next 23 patients by dual-headed camera. Side-by-side ictal-interictal SPECT evaluation and SISCOM images were blindly reviewed and classified as either localizing to one of 16 sites or nonlocalizing. A third reviewer evaluated cases of disagreement between primary reviewers. Results were compared with seizure localization by any of the following three traditional techniques: surgical outcome, invasive, and noninvasive video-EEG monitoring. The results from the single- and dual-headed SPECT cameras were compared. RESULTS: Reviewers localized areas of hyperperfusion with SISCOM images more often than with side-by-side SPECT evaluation (71.0 vs. 47.4%; p = 0.01). When we compared results of SPECT evaluation with traditional techniques, SISCOM showed greater concordance than side-by-side SPECT evaluation (60.53 vs. 36.84%; p = 0.006). There were no differences in localization between images derived from single- and dual-headed cameras. Concordance of seizure localization, compared with traditional techniques, also was not different between these groups [kappa = 0.38, 95% confidence interval (CI), 0.18-0.58] vs. kappa = 0.63, 95% CI (0.45-0.81)]. CONCLUSIONS: SISCOM is a worthwhile technique for preoperative evaluation in partial epilepsy patients and improves the sensitivity and specificity of seizure localization of SPECT images derived from both single- and dual-headed SPECT cameras.     

Ictal magnetoencephalography in temporal and extratemporal lobe epilepsy

PURPOSE: We evaluated visual patterns and source localization of ictal magnetoencephalography (MEG) in patients with intractable temporal lobe epilepsy (TLE) and extratemporal epilepsy (ETE). METHODS: We performed spike and seizure recording simultaneously with EEG and MEG on two patients with TLE and five patients with ETE. Scalp EEG was recorded from 21 channels (10-20 international system), whereas MEG was recorded from two 37-channel sensors. We compared ictal EEG and MEG onset, frequency, and evolution and performed MEG dipole source localization of interictal spikes and early ictal discharges and co-registered dipoles to brain magnetic resonance imaging (MRI). We correlated dipole characteristics with intracranial EEG, surgical resection, and outcome. RESULTS: Ictal MEG lateralized seizure onset in both TLE patients and demonstrated ictal onset, frequency, and evolution in accordance with EEG. Ictal MEG source analysis revealed tangential vertical dipoles in the anterolateral angle in one patient, and anterior dipoles with anteroposterior orientation in the other. Intracranial EEG revealed regional entorhinal seizure onset in the first patient. Both patients became seizure free after temporal lobectomy. In ETE, ictal MEG demonstrated visual patterns similar to ictal EEG and had concordant localization with interictal MEG in all five patients. Two patients underwent surgery. Ictal MEG localization was concordant with intracranial EEG in both cases. One patient had successful outcome after surgery. The second patient did not improve after limited resection and multiple subpial transections. CONCLUSIONS: Ictal MEG can demonstrate ictal onset frequency and evolution and provide useful localizing information before epilepsy surgery.