Value of non-invasive testing when there are independent bitemporal seizures in the scalp EEG

We investigated the value of non-invasive data for predicting the outcome of intracranial EEG and anterior temporal lobectomy (ATL) (follow-up>1 year) in patients who have bitemporal independent seizures in the scalp EEG. No previous report has dealt with this patient group. Independent variables were duration of epilepsy, febrile seizures, interictal and ictal scalp EEG, ictal behavior, MRI, [18F]-fluorodeoxyglucose-PET (PET) and Wada test and dependent variables were surgical outcome (seizure free or not) and localized on intracranial EEG (finding all symptomatic seizures from one temporal lobe). Non-parametric statistics were used. Of 24 patients, 20 patients had IEEG, of which 12 were localized and 8 were not. Sixteen patients had ATL and, of these, 13 (81%) became seizure free and the remaining three improved. Lateralized findings on MRI and PET, a history of febrile convulsions and shorter duration of epilepsy were all associated with a focal onset on intracranial EEG, while there was a non-significant trend with ictal behavior. The non-invasive data did not predict surgical outcome. We conclude that some of these patients can do well with surgery. In most cases, intracranial EEG is necessary for localization of seizure focus, but if PET and MRI show focal abnormalities and there is a history of febrile convulsions no further evaluation could be needed. These findings need confirmation.     

Presurgical electroencephalographic patterns and outcome from anterior temporal lobectomy.

We reviewed data from 48 patients after anterior temporal lobe resection for medically intractable epilepsy. All had ictal electro-encephalographic (EEG) evidence of unilateral temporal lobe onset. Depth electrodes were used in 19 patients. Successful surgical outcome correlated significantly with factors that suggested a temporal lobe focus, particularly in the interictal scalp EEG. The most successful outcome occurred in patients with well-localized unilateral interictal temporal spikes (100% improved). The group with well-localized bilateral temporal spikes also did well (76% improved). Patients with extratemporal spread of the interictal spike on scalp EEG, either unilaterally or bilaterally, did less well. Only one third improved, despite extensive extracranial and intracranial monitoring, when indicated. The interictal scalp EEG may be the only EEG necessary for the presurgical evaluation of selected patients with intractable temporal lobe epilepsy.     

Musicogenic seizures can arise from multiple temporal lobe foci: intracranial EEG analyses of three patients

PURPOSE: To determine the ictal-onset zone of musicogenic seizures by using intracranial EEG monitoring. METHODS: Musicogenic seizures in three patients with medically intractable musicogenic epilepsy were first localized by using noninvasive methods including, in one patient, ictal magnetoencephalography (MEG) and magnetic resonance spectroscopy (MRS). The ictal-onset zones in these patients were then further localized using by intracranial EEG monitoring, and the outcomes of the two patients who underwent epilepsy surgery were determined. RESULTS: Patient 1's musicogenic seizures localized to the right lateral temporal lobe, patient 2's originated in the right mesial temporal lobe, and patient 3's arose independently from both mesial temporal lobes. Patients 1 and 2 underwent resective epilepsy surgery and are seizure free (Engel class I). CONCLUSIONS: Musicogenic epilepsy is a heterogeneous syndrome with seizures that can arise from multiple temporal lobe foci. Patients with medically intractable musicogenic epilepsy and with unilateral ictal onset zones may be considered candidates for resective epilepsy surgery.     

Outcome after temporal lobectomy in bilateral temporal lobe epilepsy

We determined how noninvasive presurgical data relate to prognosis after temporal lobectomy in patients with independent bilateral temporal lobe (IBTL) complex partial seizures on the intracranial electroencephalogram (EEG). Between 1986 and 1994, 28 patients had IBTL seizures on intracranial EEG. Fifteen of these 28 patients underwent temporal lobectomy and 13 were not offered surgery. Of the 15 patients who had surgery, 10 patients became seizure-free. Magnetic resonance imaging (MRI) and the Wada test were the only variables associated with a seizure-free outcome. Seven of 10 seizure-free patients had a lateralized Wada result or the presence of unilateral hippocampal sclerosis, whereas none of the patients with persistent seizures had either of these findings. Variables not found to be predictive of a seizure-free outcome included location of scalp interictal spikes, degree of seizure-onset laterality, presence of early epilepsy risk factor, duration of epilepsy, and full-scale intelligence quotient. We conclude that MRI and the Wada test provide information of prognostic value in patients with bilateral temporal seizures independent of intracranial EEG data.     

Prognostic implication of contralateral secondary electrographic seizures in temporal lobe epilepsy

PURPOSE: Interhemispheric propagation of seizures in temporal lobe epilepsy is frequently noted during intracranial EEG monitoring. We hypothesized that a distinct secondary electrographic seizure (DSES) in the temporal lobe contralateral to primary seizure onset may be an unfavorable prognostic indicator. METHODS: We reviewed intracranial depth electrode EEG recordings, 1-year outcome, and medical records of 51 patients (M 29, F 22: age 15-64 years) who underwent anterior temporal lobectomy during 1988-96. We defined DSES as a seizure that spread to the contralateral temporal lobe and produced distinct contralateral EEG features. The distinct feature was focal involvement of one or two electrode contacts at onset, which starts and evolves independently from the ipsilateral temporal lobe. We considered DSES as the predominant seizure pattern when it occurred in more than one half of the patients' recorded seizures. RESULTS: Only nine of 19 (47%) patients with predominant DSES had a 1-year seizure-free outcome, whereas 27 of 32 (84%) patients without predominant DSES had a 1-year seizure-free outcome (p < 0.01). Bitemporal independent seizures were more common in patients with predominant DSES (9/19 versus 0/32; p < 0.001). CONCLUSION: Our results suggest that distinct contralateral secondary electrographic seizure is a predictor of unfavorable outcome and is also more likely to be associated with bitemporal seizures.     

Continuous Source Imaging of Scalp Ictal Rhythms in Temporal Lobe Epilepsy

Summary: Purpose: We wished to determine whether continuous EEG source imaging can predict the location of seizure onset with sublobar accuracy in temporal lobe epilepsy (TLE).
Methods : We retrospectively analyzed the earliest scalp ictal rhythms, recorded with 23- to 27-channel EEG, in 40 patients with intractable TLE. A continuous source analysis technique with multiple fixed dipoles (Focus 1.1) decomposed the EEG into source components representing the activity of major cortical sublobar surfaces. For the temporal lobe, these were basal, anterior tip, anterolateral, and posterolateral cortex. Ictal EEG onset was categorized according to its most prominent and leading source component. All patients underwent intracranial EEG studies before epilepsy surgery, and all had a successful surgical outcome (follow-up >1 year).
Results : Most patients with ictal rhythms having a predominant basal source component had hippocampal-onset seizures, whereas those with seizures with prominent lateral source activity had predominantly temporal neocortical seizure origins. Seizures with a prominent anterior temporal tip source component mostly had onset in entorhinal cortex. Seizures in some patients had several equally large and nearly synchronous source components. These seizures, which could be modeled equally well by a single oblique dipole, had onset predominantly in either entorhinal or lateral temporal cortex.
Conclusions : Multiple fixed dipole analysis of scalp EEG can provide information about the origin of temporal lobe seizures that is useful in presurgical planning. In particular, it can reliably distinguish seizures of mesial temporal origin from those of lateral temporal origin.     

Adult-onset epilepsy associated with dysembryoplastic neuroepithelial tumors.

RATIONALE: Dysembryoplastic neuroepithelial tumors (DNET) are benign, localized lesions that typically cause localization-related epilepsy of childhood onset. Although excellent seizure outcomes are expected following surgical resection of focal, benign lesions, reports in pediatric epilepsy series suggest that this may not be the case with DNETs, which may exhibit complex and often multifocal epileptogenesis. We report the characteristics and surgical outcome of an adult- and childhood-onset cohort with this condition. METHODS: Retrospective cohort of 23 patients seen at two major epilepsy centers, with localization-related epilepsy associated with histopathologically demonstrated DNETs. We assessed clinical, electrographic and surgical outcome features in patients with adult- and childhood-onset epilepsy. We were particularly interested in the level of congruence of EEG and MRI data and the need for intracranial recordings. We evaluated seizure outcomes at last follow-up. RESULTS: The mean age was 33.3 years (range: 5-56 years). Ten patients had adult-onset epilepsy. Thirteen patients (57%) had simple partial, 21 (91%) had complex partial, 16 (70%) had secondarily generalized seizures and 5 patients had only simple partial seizures. Status epilepticus did not occur. Non-enhancing lesions on MRI were located in the temporal lobe in 17 patients, the frontal lobe in 3 patients and the parietal/occipital region in 2 patients. One patient had a DNET that involved both frontal and temporal areas. Ictal scalp EEG and MRI were congruent in 17 patients (74%). Eleven patients (48%) underwent lesionectomies, while the rest required some resection of extralesional cortex as well. Five patients required intracranial EEG. There was no association with cortical dysplasia. Seventeen patients (74%) had an Engel class 1 outcome, in a follow-up period that ranging from 5 to 98 months. CONCLUSIONS: We found no difference in outcomes between adult- and childhood-onset cases. Although epileptogenicity was complex, congruence between electro-clinical and neuroimaging studies was high and allowed good surgical outcomes at 1 year of follow-up.     

Neocortical temporal lobe epilepsy: intracranial EEG features and surgical outcome.

Patients with neocortical temporal lobe epilepsy (NTLE) may have less favorable outcome with anterior temporal lobectomy than those with mesial temporal foci. The authors analyzed ictal intracranial electroencephalograms (EEGs) in patients with NTLE to identify features that predict surgical outcome. The following intracranial ictal EEG features in 31 consecutive medically intractable NTLE patients were studied: Frequency (i.e., low-voltage fast [>20 Hz], recruiting ictal-onset spikes, ictal-onset rhythms less than 5 Hz, ictal-onset rhythms with repetitive sharp waves between 5 and 20 Hz); extent of ictal onset (focal, sublobar, and lobar); localization within the temporal lobe (anterior, posterior, or regional); and the time to seizure spread outside the temporal lobe (rapid, intermediate, and slow). The average follow-up period was 36.7 months (range, 18 to 60 months). Findings between two outcome groups were compared: class I group (seizure-free) and class II to IV group (persistent seizures). Twenty-one (66.7%) of 31 patients with NTLE were seizure-free. Intracranial EEG features which were significantly associated with seizure-free outcome were focal or sublobar onset, anterior temporal onset, and slow propagation time (P < 0.05). There was a trend for patients with ictal onset morphologies of slow ictal-onset rhythm and repetitive sharp waves to be seizure-free (P = 0.07). Intracranial EEG is helpful in predicting surgical outcome in NTLE patients.     

Surgical treatment of extra‐hypothalamic epilepsies presenting with gelastic seizures

We provide an overview of the surgical outcome of extra‐hypothalamic epilepsies with gelastic seizures based on an original case report and a summary of the literature. Twenty‐two articles providing information on the outcome of resective surgery in 39 patients with extra‐hypothalamic gelastic seizures from the temporal (19 patients) or frontal lobe (20 patients) were selected. We add another case of temporal lobe gelastic seizures to the literature with a video demonstrating the mirthful component of this patient's laughing seizures. Drug‐refractory cases of gelastic seizures from the temporal or frontal lobes are amenable to surgical treatment following thorough investigation with imaging, as well as scalp and intracranial EEG.     

Depth Electrode Studies in Temporal Lobe Epilepsy: Relation to Quantitative Magnetic Resonance Imaging and Operative Outcome

Summary: We performed a retrospective study of 30 patients with presumed intractable temporal lobe epilepsy (TLE) who underwent chronic intracranial EEG monitoring (CIEM). Multicontact depth electrodes were stereotactically implanted through the medial occipital lobe into amygdala and hippocampus. All patients had previously undergone extracranial ictal EEG monitoring that proved inadequate to localize the epileptogenic zone. No morbidity as associated with CIEM in the 30 patients. Twenty-five patients were shown to have exclusively or predominantly unilateral temporal lobe seizures, and 5 patients had bitemporal seizures without unilateral predominance; 24 patients subsequently underwent an anterotemporal lobe cortical resection. Twenty-one patients have been followed a minimum of 1 year postoperatively. Nine patients (43%) had a class I outcome (seizure-free, auras only, or provoked seizures), 3 patients (14%) had a class I1 outcome (≥95% seizure reduction), 4 patients (19%) had a class III outcome (≥50% seizure reduction); and 5 patients (24%) had a class IV outcome (<50% seizure reduction or no change). A prolonged interhemispheric propagation time (p <0.01) and magnetic resonance imaging (MR1)-identified hippocampal atrophy (p <0.01) correlated with a favorable surgical outcome. Results of this study may prove useful in counseling patients who undergo CIEM before temporal lobe surgery.     

SECTION D: NEUROSURGERY & NEUROPATHOLOGY

Comparison of surgical and medical treatment for partial epilepsy. Medical and social implications of the treatment
Procedures in Pediatric Epilepsy Surgery
The possible need for intra-cranial EEG in surgery for temporal lobe epilepsy
Consistency of lateralisation in intracranial record-ings of seizures of temporal lobe origin
Comparison of lateralising capability of 99Tc^m HM-PAO-SPECT, neuropsychology, interictal and ictal EEG in the pre-surgical evaluation of patients with intractable epilepsy
Convergence of CT/MRI, "FDG-PET, intracarotid amobarbital procedure and D.EEG in presurgical evaluation of refractory partial epilepsy
Surgery for epilepsy in the United Kingdom
Anterior 2/3 callosotomy for the treatment of in-tractable epilepsy
Pre-surgical EEG evaluation
A simplified technique for epidural recording of epi-leptiform activity and seizure patterns
Discrepancy between interictal and ictal EEG-find-ings - the use of subdural electrodes may solve the problem
Temporal mesiolimbic versus temporal neocortical complex partial seizures; electroclinical correlates recorded by combined depth and subdural electrodes
Verifying electrical dipole localization in patients with epilepsy undergoing depth EEG recordings in the presurgical evaluation of intractable epilepsy
A current dipole tracing method locating interictal epileptiform activity in patients with focal epilepsy
PET-studies on distribution of glia in patients with focal epilepsy
Relationship of pre-operative neuropsychological test to the sodium amytal test - results on an empiri-cal study
Amygdalohippocampectomy in complex partial epi-lepsy     

Electro-clinical characteristics and postoperative outcome of medically refractory tumoral temporal lobe epilepsy

BACKGROUND: Very few studies have specifically addressed surgical treatment and outcome of patients with tumor-related temporal lobe epilepsy (TLE). AIM: To define the postoperative seizure outcome and the factors that influenced the outcome of patients with tumor-related TLE. MATERIALS AND METHODS: We selected patients whose surgical pathology revealed a temporal lobe neoplasm and who had completed > 1 year of postoperative follow-up. We reviewed the clinical, EEG, radiological and pathological data, and the seizure outcome of these patients and assessed the factors that influenced the outcome. RESULTS: Out of the 409 patients who underwent surgery for refractory TLE during the 8-year study period, there were 34 (8.3%) patients with temporal lobe neoplasms. The median age at surgery was 20 years and the median duration of epilepsy prior to surgery was 9.0 years. MRI revealed tumor in the mesial location in 21 (61.8%) patients. Interictal and ictal epileptiform EEG abnormalities were localized to the side of th lesion in the majority. Mesial temporal lobe structures were included in the resection, if they were involved by the tumor; otherwise, lesionectomy alone was performed. During a median follow-up of 4 years, 27 (79%) patients were completely seizure-free. The only factor that predicted long-term seizure-free outcome was being seizure-free during the first two postoperative years. CONCLUSIONS: Our results emphasize the fact that in patients with tumoral TLE, when the seizures are medically refractory, surgery offers potential for cure of epilepsy in the majority.     

难治性枕叶癫痫的术前定位与手术治疗

目的探讨难治性枕叶癫痫的术前定位与手术方法。方法对经手术治疗且随访时间6个月以上的9例枕叶癫痫患者的临床资料进行回顾性分析。采用发作症状评估、影像学检查、长程视频头皮脑电图监测、颅内电极脑电图记录等方法综合术前定位。根据术前定位确定的致痫灶部位与范围采用不同的手术方法。7例病人采用颅内电极置入术来精确定位。局部枕叶皮层切除2例,枕叶大部或全部切除4例,全枕叶或后头部脑叶离断3例;同期经枕入路切除或离断颞叶内结结构3例。结果术后随访6个月至2年,术后癫痫无发作6例,发作1次1例,发作减少90%以上2例。结论难治性枕叶癫痫经手术治疗可以取得较好的疗效,颅内电极脑电图记录有助于致痫灶准确定位,并指导术中切除部位与功能保护。     

Comparison of Mesial Versus Neocortical Onset Temporal Lobe Seizures: Neurodiagnostic Findings and Surgical Outcome

Summary: We compared historical features, surface EEG findings, results of intracarotid sodium amobarbital memory testing (IAT), and outcome after anterotemporal lobectomy (ATL) in patients with mesiotemporal lobe seizure onset with those with more diffuse temporal lobe seizure onset (intracranial EEG). Forty-eight patients evaluated consecutively between July 1985 and October 1991 with both scalp/sphenoidal and intracranial EEG were shown to have seizures originating in one temporal lobe. No patients had temporal lobe tumor or vascular malformation. Thirty-seven of the 48 patients had seizure onset in the amygdale/hippocampus (amyg/hipp). Eleven of the 48 had either temporal neocortical onset or simultaneous amydhipp and neocortical onset. Patients with mesial onset seizures were more likely to have lateralized memory impairment on I AT (p = 0.05). We noted a trend toward a difference in age of first risk for epilepsy between the two groups (p = 0.09) but not for a difference in any specific risk factor. There were no significant differences in surface EEG interictal findings. Unlike in previous studies, comparison of outcome between the two groups showed no difference in seizure-free outcome. Sudden unexpected death (SUD) was more frequent in neocortical seizure patients who were not seizure-free (p < 0.05).     

Localization of epileptogenic zone in temporal lobe epilepsy by ictal scalp EEG.

Our aim was to evaluate the ability to localize the epileptogenic zone in temporal lobe epilepsy (TLE) by ictal scalp electroencephalogram (EEG). Using simultaneous video recording, we analysed scalp EEG activity during ictal periods in 38 patients (30 patients with medial TLE (MTLE) and eight with lateral TLE (LTLE)). In 14 patients, intracranial ictal EEGs were recorded with depth electrodes, and simultaneous recordings of scalp and intracranial EEG were performed in 11 patients. Scalp EEG showed that, in all 30 patients with MTLE (71 of 72 seizures), an attenuation of background activity was observed before the appearance of ictal activity. Ictal discharges first appeared in the scalp EEG when the ictal discharges reached the lateral part of the temporal lobe on the intracranial EEG. While, in all eight patients with LTLE (25 of 25 seizures), the attenuation of background activity did not occur before the appearance of ictal activity. When the ictal discharges started in the lateral temporal lobe on intracranial EEG, ictal discharges appeared on the scalp. MTLE and LTLE could be diagnosed by the presence or absence of attenuation of background activity with clinical ictal signs before the appearance of ictal discharges.     

额叶癫痫的特点及手术治疗

目的 :分析额叶癫痫的临床特征、发作期及发作间期脑电图特点 ,探讨额叶癫痫手术治疗。方法 :应用视频脑电图对 9例额叶癫痫患者进行长程监测 ,并对其中 6例记录颅内脑电图。分析癫痫发作的临床表现及脑电图特点 ,定位致痫灶 ,行手术切除。结果 :额叶癫痫的发作特点为 :发作频繁而短暂 ,以睡眠期发作为主 ,常见过度运动 ,姿势性强直 ,发声等发作症状。发作期可见棘波节律 ,广泛低幅快活动 ,节律性慢波等特征性脑电活动。颅内电极记录可清晰显示异常脑电活动的发作起源及扩散情况 ,有助于定位致痫灶。手术切除病灶及致痫灶 ,效果满意。结论 :额叶癫痫是一组具有特征性的癫痫综合征 ,颅内电极记录有助于揭示其脑电活动变化。对于难治疗性额叶癫痫 ,准确定位致痫灶是手术成功的关键。     

Localizing value of rapid eye movement sleep in temporal lobe epilepsy

Sleep state is a physiological modulator of epilepsy. Non rapid-eye-movement (NREM) sleep generally increases interictal epileptiform discharges (IEDs) and expands their field of distribution. In contrast, rapid eye movement (REM) sleep tends to suppress IEDs and may limit their spread outside of the region of primary seizure origin. The ability of REM sleep to restrict IEDs may have localizing value in temporal lobe epilepsy patients undergoing evaluations for epilepsy surgery. We present the case of a woman with medically-refractory seizures secondary to a mesial temporal glioma. Although scalp and intracranial electroencephalographic (EEG) seizure recordings supported bilateral epileptic foci, the IEDs recorded during REM sleep were restricted to the region of the glioma, and the patient had a successful surgical outcome. Our findings support the usefulness of combining sleep recordings with EEG monitoring in the evaluation of candidates for epilepsy surgery.     

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.     

Extent of neocortical resection and surgical outcome of epilepsy: Intracranial EEG analysis

Purpose: Intracranial electroencephalography (EEG) monitoring is an important process in the presurgical evaluation for epilepsy surgery. The objective of this study was to identify the ideal resection margin in neocortical epilepsy guided by subdural electrodes. For this purpose, we investigated the relationship between the extent of resection guided by subdural electrodes and the outcome of epilepsy surgery. Methods: Intracranial EEG studies were analyzed in 177 consecutive patients who had undergone resective epilepsy surgery. We reviewed various intracranial EEG findings and resection extent. We analyzed the relationships between the surgical outcomes and intracranial EEG factors: the frequency, morphology, and distribution of ictal‐onset discharges, the propagation speed, and the time lag between clinical and intracranial ictal onset. We also investigated whether the extent of resection, including the area showing ictal rhythm and various interictal abnormalities—such as frequent interictal spikes, pathologic delta waves, and paroxysmal fast activity—influenced the surgical outcome. Results: Seventy‐five patients (42%) were seizure free. A seizure‐free outcome was significantly associated with a resection that included the area showing ictal spreading rhythm during the first 3 s or included all the electrodes showing pathologic delta waves or frequent interictal spikes. However, subgroup analysis revealed that the extent of resection did not affect the surgical outcome in lateral temporal lobe epilepsy. Conclusions: The extent of resection is closely associated with surgical outcome, especially in extratemporal lobe epilepsy. Resection that includes the area with total pathologic delta waves and frequent interictal spikes predicts a good surgical outcome.     

Comparison of bitemporal and unitemporal epilepsy defined by depth electroencephalography

Of 166 consecutive patients studied with depth electroencephalography (EEG), 87 had seizures arising from one temporal lobe and 23 had seizures arising independently from each temporal lobe. We retrospectively reviewed and compared those patients with unitemporal and those with bitemporal seizures. There was no statistically significant differences between the two groups in terms of age at onset of seizures, duration of epilepsy, localization of scalp EEG abnormalities, surgical results, or pathological findings. The bitemporal group, however, had significantly fewer patients with a history of febrile seizures (p less than 0.025). Two patients with bitemporal seizures were later found to have extratemporal lesions, and one an extrahippocampal temporal lesion, on magnetic resonance scans; one patient's extratemporal lesion was resected and all habitual seizures stopped. These findings suggest that a single pathophysiological process accounts for unitemporal and some bitemporal epilepsy, but that independent onset of seizures from each temporal lobe detected by depth EEG may also indicate extratemporal foci.