Comparative study of interictal PET and ictal SPECT in complex partial seizures

Objective – To compare the sensitivity of ictal ^99mTc-HMPAO single photon emission computed tomography (SPECT) with interictal ¹⁸F-fluorodeoxyglucose positron emission tomography (PET) in localization of the epileptogenic focus in patients with medically intractable complex partial seizures (MI-CPS). Material and methods – Retrospective analysis was performed on patients with MI-CPS who underwent anterior temporal lobectomy from January 1993 onwards when PET became available to us for clinical studies at the Indiana University Medical Center. There were 38 female and 29 male patients (total=67) with MI-CPS, 10 to 55.5 years of age (mean 31) and duration of their epilepsy from 1-46 years (mean 21). Interictal PET was evaluated for evidence of focal hypometabolism and ictal SPECT for focal perfusion abnormality (hyperperfusion or hypoperfusion) by visual analysis. Results – Both Ictal SPECT and interictal FDG-PET studies were obtained in 36 patients with MI-CPS. PET showed definite hypometabolism in 30 and questionable hypometabolism in an additional two patients. Ictal SPECT correctly localized the seizure focus in 27 patients by demonstrating ictal hyperperfusion whereas in one the hyperperfusion was falsely localized. In an additional seven patients the ictal SPECT provided probable localization by demonstrating ictal hypoperfusion in the appropriate temporal lobe. The sensitivity of ictal SPECT and interictal PET was 34/36 and 32/36, respectively, the difference was not statistically significant (χ²_y=0.18, DF=1, P=0.67). In six of the 36 patients the two tests were complementary to each other in providing localizing information. Conclusion – Ictal SPECT and interictal PET are equally sensitive and reliable techniques in localizing the epileptogenic focus in patients with MI-CPS. They play a critical role in providing localization in MRI negative patients allowing surgical resection to be undertaken in many without additional invasive electrographic monitoring.     

Single photon emission computed tomography (SPECT) brain imaging using N,N,N'-trimethyl-N'-(2 hydroxy-3-methyl-5-123I-iodobenzyl)-1,3-propanediamine 2 HCl (HIPDM): intractable complex partial seizures

HIPDM-SPECT brain imaging was performed in four patients with intractable complex partial seizures (CPS). Three patients had an epileptogenic focus in one temporal lobe and underwent anterior temporal lobectomy. Interictal HIPDM-SPECT demonstrated decreased regional cerebral perfusion (rCP) in the epileptogenic area in only one patient, but ictal studies showed increased rCP in the epileptic foci of all three patients. In the fourth patient, interictal HIPDM-SPECT showed increased rCP in the area of epileptogenic focus; when antiepileptic medication was taken, rCP decreased. HIPDM-SPECT brain imaging is useful for localizing epileptogenic foci in CPS.     

Seizure outcome after anterior temporal lobectomy and its predictors in patients with apparent temporal lobe epilepsy and normal MRI

PURPOSE: Very little reliable information is available regarding the role of anterior temporal lobectomy (ATL), optimal presurgical evaluation strategy, post-ATL seizure outcome, and the factors that predict the outcome in patients with medically refractory temporal lobe epilepsy (TLE) and normal high-resolution magnetic resonance imaging (MRI). To be cost-effective, epilepsy surgery centers in developing countries will have to select candidates for epilepsy surgery by using the locally available technology and expertise. METHODS: We reviewed the electroclinical and pathological characteristics and seizure outcome of 17 patients who underwent ATL for medically refractory TLE after being selected for ATL based on a noninvasive selection protocol without the aid of positron emission tomography (PET) or single-photon emission computed tomography (SPECT), despite a normal preoperative high-resolution MRI. RESULTS: Seven (41%) patients achieved an excellent seizure outcome; five of them were totally seizure free. An additional five (29%) patients had >75% reduction in seizure frequency. The following pre-ATL factors predicted an excellent outcome: antecedent history of febrile seizures, strictly unilateral anterior temporal interictal epileptiform discharges (IEDs), and concordant type 1 ictal EEG pattern. All the five patients with pathologically verified hippocampal formation neuronal loss were seizure free. The presence of posterior temporal, bilateral temporal, and generalized IEDs portended unfavorable post-ATL seizure outcome. CONCLUSIONS: A subgroup of patients destined to have an excellent post-ATL outcome can be selected from MRI-negative TLE patients by using history and scalp-recorded interictal and ictal EEG data. The attributes of these patients are antecedent history of febrile seizures, strictly unilateral anterior IEDs, and concordant type 1 ictal EEG pattern.     

HIPDM single photon emission computed tomography brain imaging in partial onset secondarily generalized tonic-clonic seizures

HIPDM-Single photon emission computed tomography brain imaging was performed during interictal and ictal stages in three patients with complex partial seizures and secondarily generalized tonic-clonic seizures. In all three patients, interictal studies demonstrated decreased regional cerebral perfusion (rCP) and ictal studies showed increased rCP in the epileptogenic region. The demonstration of focal hyperperfusion by SPECT performed during secondarily generalized tonic-clonic seizures suggests that rCP in the epileptic focus remains higher than in other cerebral regions during immediate postictal stages, even in secondarily generalized seizures.     

Ictal chronology and interictal spikes predict perfusion patterns in temporal lobe epilepsy: a multivariate study.

Typical (TPP) and atypical (APP) perfusion patterns (PP) may be seen in ictal SPECT of patients with temporal lobe epilepsy (TLE). APP may pose problem in the lateralization of the epileptogenic zone (EZ). We aimed to investigate predictive variables for the occurrence of TPP and APP. Fifty-one TLE patients were submitted to successful anterior-mesial temporal lobectomy. Univariate (UVA) and multivariate (MVA) analysis were performed upon clinical data, distribution of interictal spikes, and ictal chronology of seizures. From MVA, a final predictive model (FPM) was determined to better predict TPP and APP. Forty patients showed TPP (78.5%) and 11 patients APP (21.5%). Accuracy of ictal SPECT was higher in the unilateral (UIS) than in the bilateral (BIS) interictal spikes group (P = 0.05). FPM showed that patients exhibiting BIS, with shorter proportion of the electrographic seizure occurring after completion of tracer injection, and longer clinical than EEG seizure duration had more APP (P = 0.003). Generalized tonic-clonic seizures did not result in more APP. We concluded that analysis of ictal SPECT in TLE requires the knowledge of TPP and APP, the distribution of interictal spikes on temporal lobes and the ictal chronology of seizures. BIS showed that beyond a more complex epileptogenicity and seizure propagation, they may also lead to APP.     

Ictal Single Photon Emission Computed Tomography in Occipital Lobe Seizures

Summary: Purpose: Ictal single photon emission computed tomography (SPECT) has been evaluated as an adjunctive localizing technique in temporal lobe epilepsies and, to a lesser degree, in some extratemporal epilepsies. The purpose of this study was to determine whether occipital lobe seizures are associated with distinctive ictal cerebral blood perfusion (rCP) patterns.
Methods : SPECT was used with the tracer ^99mTc HMPAO to image ictal rCP in 6 patients in whom clinical, EEG, and imaging data indicated occipital lobe seizures.
Results : Two patterns of rCP were seen. Four patients had hyperperfusion that was restricted to the occipital lobe, and two patients had hyperperfusion of the occipital lobe and the ipsilateral mesial temporal lobe, with hypoperfusion of the lateral temporal lobe. The latter 2 patients had clinical and surface EEG evidence of temporal lobe involvement in the seizure discharge.
Conclusions : Ictal rCP patterns in occipital lobe seizures are distinct from those in temporal lobe seizures and may vary according to whether or not ipsilateral temporal lobe structures are involved in the ictal discharge.     

Correlation of abnormalities of interictal n-isopropyl-p-iodoamphetamine single-photon emission tomography with focus of seizure onset in complex partial seizure disorders

Single-photon emission tomography (SPECT) scanning with n-isopropyl-p-iodoamphetamine (IMP) was performed on 23 patients with complex partial seizures undergoing long-term video electroencephalographic (EEG) seizure monitoring. Twenty-one of the 23 patients had abnormalities on SPECT scanning consisting of areas of decreased activity reflecting diminished cerebral blood flow. In 15 of these 21 patients, there was good correlation between the site of the abnormality on SPECT scan and the site of origin of seizures monitored by EEG. Of the six remaining patients, four had multifocal SPECT abnormalities, with one of the abnormal areas corresponding with an ictal site. The two remaining patients had SPECT abnormalities and major ictal EEG foci in entirely different areas. In contrast to the high proportion of abnormal SPECT scans, only 10 of 23 focal abnormalities were discovered on magnetic resonance imaging (MRI) scans. Three patients who had seizures within 2 h of an initial scan were rescanned 4-5 h after injection. Focal areas of increased blood flow were noted on all three scans, although not always at the ictal site. The SPECT scan appears to be useful in interictal localization of seizure foci. Postictal scans may also be useful, although our numbers are too small to draw conclusions.     

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.     

Time from ictal subdural EEG seizure onset to clinical seizure onset: prognostic value for selecting temporal lobectomy candidates

Long-term subdural EEG recording was performed to test the hypothesis that the duration from ictal subdural EEG seizure onset (ECOT) is prognostic for seizure-free outcome following temporal lobectomy. In 48 patients with complex partial seizures, temporal lobectomy was based on invasive localization of the ictal seizure focus. Subdural EEG data were analyzed for association with seizure-free outcome (seizure-free: yes or no) at a minimum of one year following temporal lobectomy. As the duration from ictal subdural EEG seizure onset to clinical seizure onset increased, the odds of being seizure-free postoperatively increased. The best fitting statistical model for predicting seizure-free outcome included seizure onset (unilateral vs. bilateral) and duration from ictal subdural EEG seizure onset to clinical seizure onset. While selection of temporal lobectomy candidates has increasingly emphasized noninvasive recording, some scalp-EEG monitored patients cannot be offered surgery for various reasons, one of which may include ictal EEG seizure onset following clinical seizure onset. When subdural EEG monitoring is performed for selection of temporal lobectomy candidates, analysis of the duration from subdural EEG seizure onset to clinical seizure onset should improve the prognostic value of the subdural EEG data for seizure-free outcome following temporal lobectomy.     

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.     

Contralateral temporal hypometabolism on positron emission tomography in temporal lobe epilepsy

Introduction — No detailed case studies report lateralised hypometabolism on positron emission tomography (PET) contralateral to the epileptogenic focus in temporal lobe epilepsy (TLE). Material and methods — We performed ¹⁸F fluorodeoxyglucose (FDG) PET in two intractable TLE patients. Results — One had right temporal interictal spikes on electroencephalography (EEG) and a right medial temporal lobe lesion on magnetic resonance imaging (MRI). FDG-PET showed decreased uptake in the left temporal lobe. Right temporal ictal onset, with bilateral interictal epileptiform activity, occurred on intracranial EEG. He is seizure free after right temporal lobectomy and ganglioglioma resection. The second had right temporal lobe interictal and ictal EEG activity. MRI demonstrated right anteriomedial temporal increased T2 signal. Neuropsychology revealed bilateral cognitive dysfunction. FDG-PET showed left anterior temporal and lateral frontal hypometabolism. He is seizure free after right temporal lobectomy. Conclusion — These findings suggest that regional uptake asymmetry on FDG-PET may be give misleading lateralising information in TLE.     

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.     

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.     

Orbito-frontal epilepsy masquerading as temporal lobe epilepsy-a case report.

Temporal lobectomy fails to control seizures in a considerable percentage of patients who do not have hippocampal sclerosis. One theoretical reason for failure of surgery is that some of these patients may in fact have extratemporal epilepsy. We present a 28-year-old woman with clinical and scalp electroencephalogram (EEG) evidence of right temporal lobe epilepsy (TLE) supported by functional imaging with interictal positron emission tomography (PET) and ictal single-photon emission computerized tomography (SPECT). An invasive EEG monitoring was prompted by the discovery of a small right orbito-frontal lesion on MRI. Monitoring documented seizure onset at the lesion, with rapid right temporal involvement. The patient was almost seizure-free after a lesionectomy. The index of suspicion of orbito-frontal epilepsy should be high in patients with apparent TLE when the scalp EEG and neuroimaging data are not congruent, or if temporal lobe pathology cannot be identified on structural imaging.     

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.     

Factors playing a role in the increase of localized perfusion observed by single-photon emission-computed tomography during an epileptic seizure

Ictal SPECT is a valuable method for the presurgical exploration of partial epilepsy. (99m)Tc Ethyl Cysteinate Dimer stable during 6h has contributed to develop ictal studies to evaluate the location of partial seizure. The aim of this study was to investigate some factors playing a possible role on the regional increase of cerebral blood flow (rCBF) Twenty-three patients with refractory partial epilepsy (temporal epilepsy n=16, extratemporal epilepsy n=7) were included. All the patients underwent a presurgical evaluation (phase I) during a week with detailed clinical history, cranial magnetic resonance imaging, monitoring EEG and video. Ictal and interictal SPECT were performed using a fast rotating brain dedicated camera (TOMOMATIC 564) in a quiet and normally illuminated room with controlled EEG (interictal) or video EEG (ictal); Scanning was started one hour after injection of ECD Tc administered in IV a few seconds after the electrical onset seizure. Slices parallel to the long axis of the temporal lobe were reconstructed. SPECT images were evaluated after normalisation. This study shows that     

Falsely localizing ictal onsets with depth EEG telemetry during anticonvulsant withdrawal

A patient with partial complex seizures evaluated for surgery with chronic depth electrode recordings demonstrated falsely localizing ictal onsets during anticonvulsant drug withdrawal. When phenytoin was being reduced, more seizures appeared to originate from the left temporal lobe than from the right. Right anterior temporal lobectomy, performed on the basis of other findings, revealed a small unsuspected tumor in the resected specimen, and the patient has remained seizure free for 3 years. The seizures that originated from the left temporal lobe were different from the patient's habitual attacks and appeared to be the result of anticonvulsant withdrawal and, perhaps, electrode irritation. Four other patients who received anterior temporal lobectomies at UCLA between 1977 and 1980 had at least one stereotaxic EEG (SEEG)-recorded contralateral seizure onset, and all have benefited from surgery. Although multifocal SEEG-recorded ictal onsets should be considered a poor prognostic sign, distant sites that give rise to atypical seizures during drug withdrawal may not generate spontaneous seizures postoperatively. Consequently, this finding should not be used as a sole criterion against the recommendation of surgical therapy.     

The clinical usefulness of ictal SPECT in temporal lobe epilepsy: the lateralization of seizure focus and correlation with EEG

PURPOSE: To analyze the relationship between ictal electroencephalography (EEG) and ictal single-photon emission computed tomography (SPECT) and to evaluate the diagnostic usefulness of ictal SPECT as an independent presurgical evaluation technique. METHODS: Sixty-eight patients with temporal lobe epilepsy who underwent temporal lobectomy with good surgical outcome were included in this study. Ictal SPECT was performed during video-EEG monitoring. The ictal EEG was analyzed in 5-second intervals from the initiation of the ictal rhythm. Lateralized EEG dominance was determined by the amplitude, frequency, or regional patterns of ictal rhythm for each 5-second interval. The total ictal EEG was divided into three periods: preinjection (maximum, 30 seconds), the initial part of the postinjection period (30 seconds), and the latter part of the postinjection period (30 to 60 seconds). The results of ictal SPECT were compared with the lateralized EEG dominance of each period and at seizure onset. RESULTS: Fifty-four of 68 ictal EEGs correctly lateralized seizure focus ipsilateral to the side of surgery. Ictal SPECT correctly lateralized the epileptogenic temporal lobe in 61 of 68 patients (mean injection time, 29.8 seconds from onset). Multivariate analysis indicated that only the EEG dominance of the preejection period correlated significantly with the concordant hyperperfusion of ictal SPECT. Correct lateralization of ictal SPECT occurred in 10 of 14 patients with nonlateralized ictal EEG. CONCLUSIONS: Preinjection neuronal activity seems to be important for the accurate interpretation of the hyperperfused patterns of ictal SPECT. Ictal SPECT is an independent and confirmatory presurgical evaluation technique.     

Outcome after surgery in patients with refractory temporal lobe epilepsy and normal MRI.

Our purpose is to determine predictors of outcome in patients with refractory temporal lobe epilepsy and normal high resolution magnetic resonance imaging (MRI) who undergo surgical therapy. We identified 23 patients who underwent temporal lobectomy and had normal pre-operative MRI, including surface coil phased array temporal lobe imaging. All were followed at least 2 years after surgery. We graded outcome as seizure-free, > 75% reduction in seizures, or < 75% reduction in seizures. We examined pre-operative interictal and ictal electroencephalographic (EEG) findings, age of onset, gender, duration of epilepsy, risk factors, family history, physical findings, age at operation, side of operation, and pathology of resected tissue in order to determine if any of these factors were associated with outcome. Overall, 48% (11/23) of patients were seizure-free, 39% (9/23) had > 75% reduction in seizures, while 13% (3/23) had < 75% reduction in seizures. Only the EEG findings were useful in predicting outcome. When ictal onsets arose from basal-temporal regions, 61% (11/18) of patients were seizure-free, while none (0/5) were seizure-free when seizures arose from mid-posterior temporal regions (P = 0.04). Interictally, if all epileptiform patterns were localized exclusively to one basal-temporal region, a finding that invariably correlated with ictal onsets, 78% (7/9) of patients were seizure-free, while only 29% (4/14) were seizure-free if discharges were bilateral or multifocal (P = 0.04). We conclude that surgery may be a reasonable treatment for some patients with intractable temporal lobe seizures and normal MRI. The best outcomes occur when seizure onsets and interictal epileptiform patterns are exclusive to one basal-temporal region. Unfavorable outcomes are most likely to occur when ictal origins are from mid-posterior temporal regions and when interictal discharges are bitemporal or multifocal in distribution.     

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.