Fusiform gyrus epilepsy: the use of ictal magnetoencephalography. Case report

The authors report successful presurgical identification of an epileptic focus in the fusiform gyrus by using ictal magnetoencephalography (MEG), which was performed with the aid of an advanced whole-brain neuromagnetometer. A 22-year-old man had suffered from medically refractory complex partial seizures since he was 10 years of age. Seizure symptoms, magnetic resonance imaging, and ictal single-photon emission computerized tomography examinations indicated right temporal lobe epilepsy; however, ictal electroencephalography, including sphenoidal recordings, failed even to lateralize the seizure focus. The MEG studies revealed that equivalent current dipoles of interictal activities were scattered bilaterally around the medial temporal structures, but those of ictal onset and postictal activities formed a cluster in the left fusiform gyrus. After confirmation of each ictal and interictal MEG finding by using long-term electrocorticography recordings, focal cortical resection of the left inferior temporal and fusiform gyri was performed. The histopathological diagnosis was cortical dysplasia, and the patient has achieved a good seizure outcome, now 15 months after the operation. Ictal and also postictal MEG may be more specific than interictal MEG for identifying the ictal onset zone.     

Magnetoencephalography in presurgical epilepsy evaluation

The introduction of whole-head magnetoencephalography (MEG) systems facilitating simultaneous recording from the entire brain surface has led to a major breakthrough of MEG in presurgical epilepsy evaluation. Localizations of the interictal spike zone with MEG showed excellent agreement with invasive electrical recordings, were useful to clarify the spatial relationship of the irritative spike zone to structural lesions, and could attribute epileptic activity to lobar subcompartments both in temporal lobe and extratemporal epilepsy. MEG was especially useful for the study of patients with nonlesional neocortical epilepsy and of patients with large lesions, where it provided unique information on the epileptogenic zone. It could reliably localize sensorimotor cortex prior to surgical procedures adjacent to central fissure. MEG language mapping yielded concordant results with the Wada test and cortical stimulation studies. MEG localizations of epileptic activity and essential brain regions were successfully integrated into frameless stereotaxy systems providing accurate functional information intraoperatively. Because MEG and EEG yield both complementary and confirmatory information, combined MEG-EEG recordings in conjunction with advanced source modeling techniques will further improve the noninvasive evaluation of epilepsy patients and constantly reduce the need for invasive procedures. Electronic Publication     

Magnetoencephalographic mapping of the language-specific cortex.

OBJECT: In this paper the authors introduce a novel use of magnetoencephalography (MEG) for noninvasive mapping of language-specific cortex in individual patients and in healthy volunteers. METHODS: The authors describe a series of six experiments in which normative MEG data were collected and the reliability, validity, and topographical accuracy of the data were assessed in patients who had also undergone the Wada procedure or language mapping through intraoperative cortical stimulation. CONCLUSIONS: Findings include: 1) receptive language-specific areas can be reliably activated by simple language tasks and this activation can be readily recorded in short MEG sessions; 2) MEG-derived maps of each individual are reliable because they remain stable over time and are independent of whether auditory or visual stimuli are used to activate the brain; and 3) these maps are also valid because they concur with results of the Wada procedure in assessing hemispheric dominance for language and with the results of cortical stimulation in identifying the precise topography of receptive language regions within the dominant hemisphere. Although the MEG mapping technique should be further refined, it has been shown to be efficacious by correctly identifying the language-dominant hemisphere and specific language-related regions within this hemisphere. Further development of the technique may render it a valuable adjunct for routine presurgical planning in many patients who harbor tumors or have epilepsy.     

Magnetoencephalographic localization of multiple seizure foci for surgical treatment of intractable frontal lobe epilepsy: confirmation with intra-operative electrocorticography

A successfully treated case of intractable FLE, of which preoperative magnetoencephalography (MEG) provided multiple spike localization and intraoperative corticogram (ECoG) confirmed the resection area. A 22-year-old male patient, with a history of subdural abscess at the age of 14 years, had suffered frequent simple (SPSs) and complex partial seizures (CPSs) and falling attacks since the age of 16 years. Although he underwent corpus callosotomy at the age of 17 years, additional surgical treatment was considered because of intractable and more frequent SPSs and CPSs. Magnetic resonance (MR) imaging demonstrated diffuse lesions in the right frontal lobe. Although, both interictal and ictal electroencephalography (EEG) failed to show focal epileptogenic localization, interictal MEG localized several clusters over the multiple anatomical lesions in the right prefrontal and frontal opercular regions. The patient underwent right fronto-temporal craniotomy, and anterior frontal lobectomy, followed by lesionectomy of the premotor area based on the intraoperative ECoG findings. The ECoG localized frequent spike discharges over the right prefrontal, frontal operculum and premotor cortices, which showed good correspondence with the MEG findings. MEG can be a useful noninvasive method for presurgical evaluation of intractable FLE.     

Neuromagnetic assessment of epileptogenicity in cerebral arteriovenous malformation

Magnetoencephalographic (MEG) activities were recorded in five patients with cerebral arteriovenous malformation (AVM) who presented with epilepsy and no clinical history of intracranial hemorrhage, using a 37-channel DC superconducting quantum interference device (SQUID) system. While scalp-recorded electroencephalograms (EEG) failed to reveal paroxysmal discharge, MEGs demonstrated localized high frequency magnetic activity (HFMA). Magnetic source imaging (MSI) depicted the accumulation of equivalent current dipole (ECD) originating from HFMA around the nidus, and the ECD localization agreed well with spike localization on intraoperative electrocorticography (ECoG). These areas corresponded with the areas of hypoperfusion on single photon emission tomography and the intraoperative laser Doppler flow meter. We discussed the application of MEG in estimating interictal paroxysmal activity sources in patients with AVM and addressed the questions of its reliability and validity in source localization. Received: 16 August 1999 / Accepted: 14 March 2000     

Timing and spatial distribution of somatosensory responses recorded in the upper bank of the sylvian fissure (SII area) in humans

We studied responses of the parieto-frontal opercular cortex to electric stimuli, as recorded by intra-cortical electrodes during stereotactic EEG presurgical assessment of patients with drug-resistant temporal lobe epilepsy. After electrical stimulation of the median nerve at the wrist, we consistently recorded a negative-positive biphasic response peaking at 60 ms (N60) and 90 ms (P90) post-stimulus in the upper bank of the sylvian fissure contralateral to stimulation. Talairach stereotactic coordinates of the electrode contacts recording these responses covered the pre- and post-rolandic part of the upper bank of the sylvian fissure (25相似文献   

Presurgical functional mapping of the sensorimotor area using evoked magnetic fields

In the present study, we evaluated the usefulness of magnetoencephalography (MEG) for presurgical identification of not only the central sulcus by somatosensory evoked magnetic fields (SEFs), which is a well-known, reliable technique, but also the primary hand motor area by movement-related cerebral magnetic fields (MRCFs). Subjects were 10 patients with brain tumor (6 glial tumors, 3 cavernous angiomas, and 1 metastatic tumor) around the sensorimotor area. Identification of the central sulcus by SEF responses to multiple sites of stimulation (median nerve, tibial nerve, thumb, and lower lip) was performed in all patients, and identification of the hand motor area by MRCF responses to the index finger extension task was made in 9. All MEG data were superimposed on sectional or three-dimensional magnetic resonance (MR) images. The central sulcus was clerAly identified by SEFs in all patients, even in 5 whose MR images showed severe distortion, and the primary hand motor area was identified by MRCFs in 6 of 9 patients. The central sulcus and primary motor area identified by MEG were confirmed by cortical recording of somatosensory evoked potentials in response to median nerve stimulation in 7 patients and motor evoked potentials in response to direct cortical stimulation in 5. All patients underwent tumor removal guided by functional mapping by MEG and experienced no surgical complications. In conclusion, MEG is a useful tool in presurgical functional mapping of the sensorimotor area. This is the first report of a case in which identification of the hand motor area by MRCFs was used in a clinical setting.     

Epilepsy surgery during infancy and early childhood in France

BACKGROUND AND PURPOSE: We present the epilepsy surgery activity in infants and children at the Fondation Rothschild Hospital, the main center dedicated to this activity in France. METHOD: A prospective study was conducted from 2003 to 2007 based on three populations: (1) children selected as candidates for surgery, (2) children undergoing presurgical evaluation and (3) children undergoing surgical procedures for epilepsy. RESULTS: Children selected as candidates for surgery: 304 children were referred and discussed by our multidisciplinary staff. They came from Paris and its suburbs (40%), the provinces (43%) or from other countries (14%). Sixty-one percent of them were included in our surgery program and 24% were excluded. Sixty-one percent of them were under 10 years of age. Children undergoing presurgical evaluation: 296 children were recorded: 140 EEG (47%), 46 with foramen ovale electrodes (16%) and 110 with invasive recording techniques (37%). Seventy percent of these children were under 10 years of age. Children undergoing surgical procedures: 316 children underwent surgery; 68% of them were under 10 years of age. The surgical procedures were focal resection (136 children), vertical parasagittal hemispherotomy (77 children), resection and or disconnection for hypothalamic hamartoma (69 children) and 34 had palliative surgery (callosotomy or vagal nerve stimulation). CONCLUSION: Eighty to 100 children undergo surgery each year in our department for drug-resistant partial epilepsy; 70% of them are less than 10 years of age. This activity is part of a network of pediatric neurologists who are deeply involved in treatment of severe epilepsy in children.     

Presurgical evaluation and surgical treatment of medically refractory epilepsy

Thanks to todays modern imaging examination techniques and especially to the common use of intracranial electrodes for localizing seizure foci, more and more patients with partial epilepsy can be treated microsurgically. The results of such neurosurgical therapies are very good, particularly in mesial temporal lobe epilepsy. In recent years, good results (60–70% seizure freedom) have also been achieved in extratemporal epilepsy surgery, so that such procedures can now be recommended for carefully selected patients. In this review, presurgical evaluations and the different surgical approaches are presented.Commentaries on this paper are available at and     

Functional imaging of the auditory cortex: role of magnetoencephalography

We present the different methods for detecting cerebral activity in the auditory cortex. Positron emission tomography (PET) and functional MRI (fMRI) measure such activity indirectly by calculating the blood flow rate or the consumption of oxygen. The direct methods of detection record the electrical or magnetic activity by eletroencephalography (EEG), or magnetoencephalography (MEG), respectively. The aim of this study was to define the role of MEG amongst these different techniques using the data from recordings of evoked magnetic fields in 5 healthy subjects. The localizations demonstrated the tonotopic organization of the auditory cortex, with high-pitched sounds showing a more medial cortical projection than low-pitched sounds. These various techniques are complementary. PET allows a pharmacological study of the cortex, and could be used in patients with cochlear implants. FMRI is non-invasive, and has a high spatial resolution. EEG has an excellent temporal resolution, and EEG recordings do not require major equipment or infrastructure. MEG has a better spatial resolution, with the same temporal resolution, as EEC. MEG is particularly useful in the localization of the cortical generators of middle-latency auditory evoked responses.     

History of epilepsy surgery at The Hospital for Sick Children in Toronto, Canada

OBJECTIVE: To review the development of epilepsy surgery for pediatric patients with intractable epilepsy at The Hospital for Sick Children in Toronto, Canada. METHODS: We retrospectively collected and reviewed published papers regarding pediatric epilepsy surgery since 1930's. RESULTS: First, McKenzie started a hemispherectomy for children. Hendrick established anatomical hemispherectomy for pediatric patients with hemiparesis and intractable seizures since 1964. Hoffman performed anterior temporal lobectomy and neocortical temporal resection for lesional tempolal lobe epilepsy with or without mesial temporal sclerosis since 1974. Thereafter, multimodal neuroimaging studies of CT scan, MRI, and XenonCT, SPECT and PET have been used to identify and remove the epileptogenic lesion and zone. In 1996, magnetoencephalography (MEG) was introduced to localize interictal spike sources and somatosensory evoked fields for children with intractable seizures. Snead and Rutka started subdural grid electrodes that were constructed by scalp video EEG, MRI and MEG findings.The clustered MEG spike source coregistered with the intraoperative neuronavigation system delineated the epileptogenic zone requiring completely excision for neocortical lesional epilepsy from 2000. CONCLUSION: The pediatric epilepsy surgery at the Hospital for Sick Children has been progressing from anatomical hemispherectomy to complete clusterectomy of MEG spikes sources that localized the epileptogenic zone. Cortical excision, lobectomy, hemisphelotomy, corpus callosotomy and vagal nerve stimulation have been applied to appropriate seizure types identified by advanced neurodiagnostic modalities. We furthermore develop non-invasive methods for localizing and understanding the epileptic network in pediatric epilepsy patients with developing brain.     

Successful radiosurgical treatment of lesional epilepsy of mesial temporal origin.

We report a case of successful radiosurgical treatment of lesional epilepsy of mesial temporal origin. A patient presented with a 2-year history of medically intractable complex partial seizures associated with a mesial temporal angioma. Interictal scalp EEG and MEG showed focal epileptiform activity around the lesion. 99mTc-HMPAO-SPECT and 18F-FDG-PET demonstrated depressed blood flow and glucose metabolism in the corresponding temporal lobe. The patient underwent gamma knife radiosurgery for the causative lesion with a low marginal dose of 18 Gy. After treatment, the partial attack ceased without shrinkage of the lesion or peri-lesional parenchymal radiation injury.     

Structural and functional imaging: particularities in children

Surgery of partial epilepsies in childhood has largely benefited from the recent advances of imaging techniques, which carry a triple goal: (1) to contribute to the localization of the epilepsy onset zone, (2) to detect and delineate an underlying lesion, and (3) to study the spatial relationship between the epileptogenic zone and the neighboring functional cortex, in order to select patients and plan the resection. This noninvasive presurgical imaging workup must be compared to clinical and electrical data to estimate the postoperative prognosis, while invasive techniques such as SEEG, cortical stimulations, and IAT often remain indispensable in difficult cases, i.e., in cryptogenic epilepsies. As in adults, advances in MRI allow us to detect more and more subtle underlying lesions, but this requires repeating MR studies during early childhood and using adapted sequence parameters to account for ongoing myelination. Ictal SPECT and PET imaging prove especially useful in planning depth electrode placement when video-EEG is not contributive, when MRI looks normal or shows multiple abnormalities, or in cases of discrepant findings. Multimodal imaging greatly enhances the sensitivity of all of these techniques. Finally, functional MRI of motor and language functions provide noninvasive cortical mapping of essential functions, using age-adapted paradigms, in cooperating children from age five to six and from IQs around 60.     

Magnetoencephalographic localization of interictal spike sources. Case report

The reliability of localization of interictal spike sources using magnetoencephalography (MEG) was examined by repeated measurements in a patient with temporal lobe epilepsy. During two preoperative recording sessions, the estimated sources, projected onto magnetic resonance images of the patient's brain, were found to lie less than 1 cm apart within the area subsequently resected. The MEG localization was in close agreement with intraoperative cortical recordings.     

Positron emission tomography: which indications, which benefits?

Positron emission tomography (PET) is currently used in the presurgical workup for drug-resistant partial epilepsies in addition to MRI. Interictal metabolism is studied in clinical practice using (18)fluoro-desoxy-glucose ((18)FDG). In medial temporal lobe epilepsy (MTLE) associated with hippocampal sclerosis, hypometabolism ipsilateral to the epileptogenic focus is found in 70-90% of cases. However, hypometabolism is larger than the structural lesion observed on MRI and includes the epileptogenic zone and ictal discharge spread areas. Hypometabolism is related to surgical outcome and cognitive disturbances in MTLE. Although the usefulness of PET appears less well-established in extratemporal lobe epilepsy and in children, its sensitivity may be improved by coregistration and superimposition of PET on MRI at any age. Focal hypometabolism can be easily detected by visual analysis, allowing detection of minor gyral abnormalities that may correspond to focal cortical dysplasias. Moreover, in cases of negative MRI, focal hypometabolism findings may help invasive monitoring planning and deep electrode placement for SEEG, and finally improve surgical outcome.     

Consistency of interictal and ictal onset localization using magnetoencephalography in patients with partial epilepsy

OBJECT: The aim of this study was to evaluate the spatial accuracy of interictal magnetoencephalography (MEG) in localizing the primary epileptogenic focus in comparison with alternative MEG-derived estimates such as ictal onset recording or sensory mapping of the periphery where seizures manifest. METHODS: During this retrospective study of 12 patients with epilepsy who had undergone successful magnetic source (MS) imaging with the aid of a dual 37-channel biomagnetometer as well as simultaneous MEG/electroencephalography (EEG) recordings, ictal events were observed in five patients and quantitative comparisons of interictal spike and ictal seizure onset source localizations were made. In the eight patients who had presented with sensorimotor seizure, source localization of cortical sites concordant with seizure foci was determined using somatosensory functional mapping, and the results were quantitatively compared with interictal spike source localizations. Interictal spike sources demonstrated on MEG localized to the same region as the corresponding ictal event or somatosensory source localizations. The mean distance between the ictal foci and interictal spike sources was 1.1 +/- 0.3 cm. Results of functional somatosensory mapping in patients with sensorimotor seizures demonstrated that seizure sources consistently colocalized with interictal MEG spike sources, with a mean distance of 1.5 +/- 0.4 cm. No systematic directional bias was observed. Interictal sources tended to be tightly clustered, and the mean ellipsoid volume, defined by one standard deviation of the source spatial coordinates, was 1 cm3. CONCLUSIONS: Interictal spike localizations on MEG were concordant with ictal and, where relevant, functional somatosensory mapping localizations. These findings support the interpretation of interictal spikes on MEG as a useful and effective noninvasive method for localizing primary seizure foci.     

Cerebral cavernous malformations and intractable epilepsy: the limited usefulness of current literature

Background  

Cerebral cavernous malformations (CCM) are known to be highly epileptogenic lesions. A number of studies on CCM surgery deal with CCM-associated seizures and/or epilepsy. In order to counsel patients with CCM-associated epilepsy, clear results from such studies would be highly useful. This study reviews the current literature with the aim to assess its usefulness for presurgical decision-making with emphasis on differentiating outcomes in different epilepsy types.     

Epilepsy surgery: when thinking about? Who are the good candidates?

Epilepsy surgery concerns any patient with pharmacoresistant partial epilepsy, responsible for disability. Children and adult patients can be candidates for epilepsy surgery. A presurgical evaluation, adapted to each patient, must identify the most precisely the cortical area, where the seizures originate, using converging data: the clinical and electroencephalographic semiology of the seizures, the structural and sometimes functional brain imagings, and evaluate if the removal of the epileptogenic focus may induce a neurological or cognitive deficit, using neuropsychological tests and sometimes functional brain imagings. Such therapeutical strategy should be evoked as soon as possible in patients for whom the epilepsy becomes pharmacoresistant, and these patients should be oriented in specialized centres. The results of epilepsy surgery vary according to the lobar origin of the epileptogenic focus and to the existence of a visible lesion on brain MRI. A multidisciplinary evaluation of the benefits and risks should be presented to the patient. Results of the surgery are usually excellent when a focus is clearly identified and the neuropsychological tests did not predict a deficit.     

Social rehabilitation after epilepsy surgery

No strict relationship has been observed between seizure outcome after surgery and the psychosocial status of patients with refractory epilepsy. The main reason is that seizures are not the sole criteria in evaluating social outcome. The presurgical status in terms of education, the mainly neuropsychological associated handicap, socio-occupational life, and the expectations of the patient must be taken into account.Psychosocial adjustment after surgery needs to be prepared long before surgery, in full cooperation with the patient and his or her family. Standardized tools must be developed to allow for a multidisciplinary approach and an objective evaluation of the psychosocial status of epileptic patients after surgery.     

Temporo-mesial epilepsy surgery: outcome and complications in 100 consecutive adult patients

Summary Background. We studied the surgical outcome, and the complications in a group of 100 consecutive adult patients with medically refractory epilepsy arising from the temporo-mesial structures. Methods. Hundred patients were treated surgically between 1994 and 2003 for drug-resistant epilepsy involving the temporo-mesial structures. All of them underwent a comprehensive noninvasive presurgical evaluation. Fourty-eight of them underwent depth electrodes recordings (according to the Talairach’s StereoElectroEncephaloGraphic (SEEG) methodology) because the noninvasive investigations were not congruent enough to identify the epileptic zone. The patients presenting with any space-occupying lesion, or with a cavernoma, or with a strictly lateral neocortical epileptic focus, were excluded. The MRI-examination was abnormal in 87 cases, displaying a hippocampal atrophy in 69 cases. The extent of temporal resection was planned according to the results of the presurgical investigation in each particular patient. Consequently, this “tailored” resection varied from selective amygdalo-hippocampectomy (6 cases), to anterior temporal lobectomy (76 cases), or to total temporal lobectomy (18 cases). Findings. The mean post-operative follow-up period was 53 months. 85 patients were found to be in Engel’s class I post-operatively (free of disabling seizures), among them 74 were in class Ia (totally seizure free). Nine patients were in Engel’s class II and six were in Engel’s class III or IV (failures). There was no surgical mortality. Three patients had a postoperative hematoma; two patients required a shunt insertion; in three patients meningitis occured; and two patients had postoperative ischaemia of the anterior choroidal artery territory, which resulted in a mild permanent hemiparesis. Neuropsychological complications are not addressed in detail in this article. Conclusions. These data indicate that “tailored” resective surgery for temporo-mesial epilepsy can be performed with a low rate of morbidity, and is highly efficacious. The use of invasive presurgical investigation (SEEG) may explain this high rate of success.