Foramen Ovale Electrodes Research Articles

Valor pronóstico de la electrocorticografía en la epilepsia temporal: patrones de la relación mesial y neocortical

Electrocorticography (ECoG) monitoring in temporal lobe epilepsy (TLE) has been employed since the 40 s as a means to delineate surgical removal especially in lesional epilepsy, to reduce resection size and decrease cognitive sequelae (memory, naming). However in recent years, ECoG has been claimed to lack indications and prognostic value in cases of non lesional TLE. On the grounds of the pathophysiological relationship between mesial structures and neocortex (through propagation pathways) we have suggested a classification of ECoG activity patterns regarding the activities simultaneously recorded in mesial and neocortical grids. Two experienced neurophysiologists (over 200 ECoG performed) have independently reviewed the recordings (including video EEG monitoring with foramen ovale electrodes) of 33 consecutive (28 non-lesional) TLE patients with the major criterion of a leading activity in mesial or neocortical areas, and related the results to the clinical course. As a result we identified five patterns: I. Pure mesial; II. Mesial with neocortial-related activity; III. Non-related mesial and neocortical activities; IV. Neocortical preponderance (although some mesial unrelated discharges may be seen), and V. Neocortical origin. In all 33, a tailored, ECpG-guided two-steps resection was performed. Surgical success significantly (c2 test) associated with patterns I, II and IV. Pattern V precluded a good outcome. ECoG reflects the state of pathological involvement of neocortex and mesial structures. An expertise approach, although brief in time (20-30 min), may either lead to preservation of relevant tissue (patterns I, II) and to establish a prognosis on the grounds of the initial epileptogenic activity.

Displasia cortical focal y epilepsia farmacorresistente. Tratamiento con cirugía

Focal cortical dysplasia (FCD) is an unusual cause of refractory epilepsy, in which the morbid anatomy is characterized by cortical laminar dysplasia and the presence of balloon like cells. A 36 year old woman who had had drug-resistant epilepsy since the age of 9 years old, with daily complex partial seizures and seizures in which she fell to the ground. After many therapeutic trials, at the age of 29 years she had a callostomy as palliative treatment for the seizures in which she fell and was completely cured of these. The complex partial seizures increased in frequency, in spite of high doses of multiple drugs, so the possibility of resective surgery was considered. A surface EEG with predominant lateralization and localization to the left temporal lobe, ictal and interictal cerebral SPECT, PET and MR were done. The findings were comparable with two foci of dysplasia in the left cerebral hemisphere, one superior parietal and the other posterior basal temporal in situation. Finally, video-EEG monitoring with foramen ovale electrodes showed ictal activity starting in the left posterior temporal regions and with rapid homolateral anteromesial diffusion. A left temporal lobectomy and amigdalohippocampectomy was done with resection of a posterior basal temporal lesion. This reduced the number of seizures by 90%, with minimal dysnomy as a sequel. The findings on morbid anatomical study were compatible with a FCD. FCD is a cause of refractory epilepsy which may benefit from surgical treatment, with excellent results, after suitable pre-operative surgical evaluation and planning, including hippocampal evaluation since there is a high incidence of associated mesial sclerosis.

Analysis of EEG data from weak-field magnetic stimulation of mesial temporal lobe epilepsy patients

Ten patients suffering from mesial temporal lobe epilepsy were exposed to weak, DC magnetic field stimulation following computer-controlled protocols established in previous studies. Poisson statistical analysis of the ten patients undergoing semi-invasive (foramen ovale) electrode monitoring reveals that for at least one experimental protocol, application of DC magnetic fields alters interictal epileptiform spike activity in five of ten patients. Similar results also have been observed in the analysis of both human and rat brains by employing weak, alternating magnetic field stimulation. Further study is necessary in order to optimize the magnetic field exposure protocol.

Presurgical evaluation: current role of invasive EEG.

Our purpose was to review the current role of invasive and semi-invasive EEG in the presurgical evaluation of candidates for epilepsy surgery. The use of stereotactically implanted intracranial depth (stereo-EEG), subdural strip and grid, and foramen ovale electrodes, as well as intraoperative electrocorticography and electrical brain stimulation ("functional mapping") at the Epilepsy Center University Hospital Zurich, from 1984 to 1998, is analyzed. Advantages and disadvantages of the various intracranial EEG techniques are critically discussed. Out of 422 selective amygdalohippocampectomies performed in Zurich, 54% had non-invasive, 32% had semi-invasive, and 14% had invasive presurgical EEG evaluation. Because patients currently referred to our center increasingly present with a complex history of disease, i.e., constitute so-called "difficult cases", there is trend to combine several invasive and semi-invasive, pre- and intraoperative neurophysiological techniques.

Cisternal S100 protein and neuron-specific enolase are elevated and site-specific markers in intractable temporal lobe epilepsy.

In the brain, S100 protein and neuron-specific enolase (NSE) are mainly found in glial cells and neurons, respectively. We investigated concentrations of S100 protein and NSE in cisternal cerebrospinal fluid obtained during implantation of foramen ovale electrodes in eight patients with temporal lobe epilepsy (TLE). In addition, the meningeal markers cystatin-C and beta-trace as well as total protein were measured. Patients with trigeminal neuralgia (TN) undergoing glycerol rhizotomy served as controls. S100 protein and NSE levels ipsilateral to the site of seizure onset were significantly higher than in TN. Contralateral TLE values were also markedly but not significantly elevated. The meningeal markers cystatin-C and beta-trace protein as well as total protein did not differ in TLE and TN. We conclude that interictal temporal lobe dysfunction corresponds with neuronal and glial marker elevations in the extracellular space and that site-specific elevations may predict the site of seizure origin biochemically.

Neuronal complexity loss in interictal EEG recorded with foramen ovale electrodes predicts side of primary epileptogenic area in temporal lobe epilepsy: a replication study.

To investigate whether a correct lateralization of the primary epileptogenic area by means of neuronal complexity loss analysis can be obtained from interictal EEG recordings using semi-invasive foramen ovale electrodes. In a previous study with recordings from intrahippocampal depth and subdural strip electrodes it was shown that the dynamics of the primary epileptogenic area can be characterized by an increased loss of neuronal complexity in patients with unilateral temporal lobe epilepsy (TLE). Neuronal complexity loss analysis was applied. This analysis method is derived from the theory of nonlinear dynamics and provides a topological diagnosis even in cases where no actual seizure activity can be recorded. We examined interictal EEG recorded intracranially from multipolar foramen ovale electrodes in 19 patients with unilateral TLE undergoing presurgical evaluation. The primary epileptogenic area was correctly lateralized in 16 of the 19 investigated patients. The misclassification of the side of seizure onset in three patients might be attributed to the larger distance between the foramen ovale electrodes and the mesial temporal structures as compared to intrahippocampal depth electrodes. Our results confirm the previous findings and provide further evidence for the usefulness of nonlinear time-series analysis for the characterization of the spatiotemporal dynamics of the primary epileptogenic area in mesial temporal lobe epilepsy.

Cost-efficient localization of seizures of mesiotemporal onset with foramen-ovale electrodes

Foramen ovale (FO) electrodes can identify mesiotemporallobe (MTL) seizure onsets but are infrequently used in the USA. Ten patients with presumed MTL ictal onset, unlocalized noninvasivelYI had FO electrodes inserted during long term monitoring for epilepsy. Placement was facilitated by intraoperative use of oblique submental and modified Caldwell view fluoroscopy. Eighty percent of patients had ictal localization by FO electrodes. This led to anterior temporal lobectomy in six with 83% being seizure free after follow-up of 20–32 months. The mean total costs of placing these electrodes was approximately half that of subdural strips and a quarter that of depth electrodes. Foramen ovale electrodes represent a costeffective and efficient method of seizure localization when noninvasive workup suggests but is not definitive for MTL origin. [Neural Res 1998; 20: 153–160]

Clinical challenges in invasive monitoring in epilepsy surgery.

Invasive monitoring aids in selecting patients for epilepsy surgery. This article reviews the methods employed to obtain intracranial EEG, data interpretation, and problems that arise during intracranial investigations. The relative merits of depth, subdural, epidural, and foramen ovale electrodes are reviewed, and a strategy for their use is suggested. Characteristic interictal and ictal EEG findings are summarized, and the problems encountered in interpreting data are discussed.

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

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

Regional "rigidity" of background EEG activity in the epileptogenic zone.

Spectral analysis of interictal background EEG activity recorded through foramen ovale (FO) electrodes during monitoring (mean 5.8 days per patient) was studied in 10 medically refractory complex partial seizure (CPS) patients who were candidates for epilepsy surgery. Data of the spectral analysis was plotted as compressed spectral array (CSA) with spectral edge frequency (SEF) markers. For each patient, time-varying fluctuations of the SEF markers were compared visually and by a computer-assisted method between two symmetrical FO electrode EEG channels recording from both mesiobasotemporal lobes (MTL). The amount of asymmetrical variations of the SEF markers ("rigidity" phenomenon) was first determined visually and then quantified by the computer-assisted method. These findings were correlated with the results of other clinical tests, including FO electrode-recorded seizure onset (FO ict), positron emission tomography with [18F]fluorodeoxyglucose (FDG-PET), and magnetic resonance imaging (MRI) to investigate whether the rigidity phenomenon could lateralize the primary epileptogenic zone. The rigid side had 80, 70, and 60% coincidence rates with the pathologic side indicated by FDG-PET, FO ict, and MRI, respectively, in a single test. We conclude that the rigidity phenomenon of FO electrode-recorded interictal background EEG activity is a valuable sign for lateralization of the primary epileptogenic zone in MTL epilepsy. The relative invariance of SEF may be caused by interictal deafferentation of epileptic neurons.

Foramen ovale and epidural peg electrodes.

Acta Neurologica ScandinavicaVolume 89, Issue S152 p. 39-43 Foramen ovale and epidural peg electrodes H. Holthausen, Corresponding Author H. Holthausen Epliepsy Center Bethel, Bielefeld, GermanyaEpilepsy Center Bethel, Clinic Mara I, Maraweg 21, 33617 Bielefeld 13, GermanySearch for more papers by this authorS. Nochtar, S. Nochtar Epliepsy Center Bethel, Bielefeld, GermanySearch for more papers by this authorH. Pannek, H. Pannek Epliepsy Center Bethel, Bielefeld, GermanySearch for more papers by this authorA. Ebnar, A. Ebnar Epliepsy Center Bethel, Bielefeld, GermanySearch for more papers by this authorI. Tuxhorn, I. Tuxhorn Epliepsy Center Bethel, Bielefeld, GermanySearch for more papers by this author H. Holthausen, Corresponding Author H. Holthausen Epliepsy Center Bethel, Bielefeld, GermanyaEpilepsy Center Bethel, Clinic Mara I, Maraweg 21, 33617 Bielefeld 13, GermanySearch for more papers by this authorS. Nochtar, S. Nochtar Epliepsy Center Bethel, Bielefeld, GermanySearch for more papers by this authorH. Pannek, H. Pannek Epliepsy Center Bethel, Bielefeld, GermanySearch for more papers by this authorA. Ebnar, A. Ebnar Epliepsy Center Bethel, Bielefeld, GermanySearch for more papers by this authorI. Tuxhorn, I. Tuxhorn Epliepsy Center Bethel, Bielefeld, GermanySearch for more papers by this author First published: March 1994 https://doi.org/10.1111/j.1600-0404.1994.tb05184.xCitations: 5AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume89, IssueS152March 1994Pages 39-43 RelatedInformation

MEG and EEG in epilepsy: is there a difference?

Interictal epileptiform activity recorded by scalp EEG, foramen ovale electrodes and MEG is discussed. Gross differences in waveform between the electric and magnetic records are discussed in the light of intracranial depth recordings.

Brain-stem lesions in the course of a presurgical re-evaluation by foramen-ovale electrodes in temporal lobe epilepsy

Two of 4 patients who were re-evaluated by means of foramen-ovale electrodes in the course of presurgical monitoring suffered a brain-stem lesion. Only 1 of these 2 patients already had a temporal resection. None of 55 patients who underwent this procedure for the first time had such a complication. We conclude that this electrode technique is not indicated to evaluate patients a second time, even if no surgical resection has been performed between the 2 recording sessions.

Transcranial magnetic stimulation (TMS) of the brain in patients with mesiotemporal epileptic foci.

Transcranial magnetic stimulation (TMS) of the human brain is mainly used for the diagnosis of diseases with disturbed central motor conduction. Recent studies revealed controversial results concerning the possibility of a TMS-induced specific activation of epileptogenic foci in patients with localization-related epilepsies, which would make TMS an additional diagnostic tool for the presurgical localization of the primary epileptogenic zone. We applied TMS to 19 patients with complex-partial seizures and investigated its effects and safety. In 12 patients we performed TMS during scalp electroencephalogram (EEG) recordings. The remaining 7 patients with localization-related epilepsies of mesiobasal limbic seizure origin underwent EEG with additionally implanted foramen-ovale-electrodes (FOE). We did not notice any significant spike activation and even observed bilateral reduction of epileptic activity in some patients. On the contrary, hyperventilation induced a marked activation of the epileptic focus. Our findings support that TMS is safe since adverse effects did not occur. However, due to possible safety hazards, TMS in epileptic patients still requires cautious application until more data will be available.

Analysis of Foramen Ovale Electrode‐Recorded Seizures and Correlation with Outcome Following Amygdalohippocampectomy

We report a detailed electroclinical analysis of 320 seizures recorded by foramen ovale electrodes in 77 potential candidates for selective temporal lobe surgery because of antiepileptic drug-resistant seizures. The exact localization of the origin of seizure discharges, the electroencephalographic (EEG) seizure onset patterns, transhemispheric propagation, propagation time, duration of discharge, laterality of discharge termination, postictal focal slowing, correspondence between foramen ovale recordings and the scalp EEG, and the influence of antiepileptic drug modifications were studied and correlated with the clinical seizure semiology and with postoperative outcome following selective amygdalohippocampectomy. In general, the foramen ovale electrode technique provided good neurophysiological information in candidates for selective amygdalohippocampectomy. The following ictal signs predicted a good surgical outcome: (a) unilateral and anterior mediobasal temporal lobe seizure onset, (b) short seizure duration, (c) no or infrequent contralateral seizure discharge propagation, and (d) if propagation to the contralateral mediobasal temporal lobe occurred, the postoperative outcome was better the later the contralateral mediobasal temporal lobe was affected. Postoperative outcome was also better the less frequently contralateral interictal spikes occurred. No direct predictive value could be attributed to the presence of an initial arrest reaction.

A new class of electrodes of ‘Intermediate Invasiveness’: Preliminary experience with epidural pegs and foramen ovale electrodes in the mapping of seizure foci

Non-invasive electroencephalographic (EEG) recording with scalp and sphenoidal leads is often insensitive to precise localization of ictal onset, and can be distorted by skull defects and underlying lesions or deformities of the brain. We present preliminary experience with epidural pegs and foramen ovale electrodes used in 30 cases of intractable partial epilepsy where non-invasive EEG did not define a zone of epileptogenesis with sufficient precision to recommend resection, or to dictate precise placement of depth electrodes or subdural girds. Custom designed mushroom shaped peg electrodes were implanted via 4.5 mm twist-drill skull holes for epidural recording from cortical areas of suspected epileptogenesis. Foramen ovale electrodes (flexible 3-contact leads) were introduced via percutaneous puncture of Meckel's cave cistern for recording from mesiotemporal regions. Chronic recording was performed for 4 to 26 days (mean 9.2 days). There were no serious complications and signal quality was excellent in every electrode. Based on interictal and ictal records, resective surgery was performed in 8 cases, more focused further invasive recording was recommended in 15 cases (with subsequent resective surgery), and surgical options were excluded in 7 cases. It is concluded that these electrodes of 'intermediate invasiveness' represent a safe and effective tool in the armamentarium for mapping complicated or elusive epileptic foci. They can be used in lieu of, in addition to, or prior to more invasive measures. Their greatest advantage lies in their relative safety and ability to survey extensive zones of suspected epileptogenesis so as to guide and focus further mapping and surgical intervention.

The neocortico to mesio-basal limbic propagation of focal epileptic activity during the spike-wave complex

In order to localize epileptogenic electrophysiological sources, a multichannel MEG system was used in 3 patients with partial epilepsy during presurgical evaluation. MEG and EEG (including scalp, sphenoidal and intracranial foramen ovale electrodes) were recorded simultaneously during a period of intensive video-EEG monitoring in order to observe single spontaneous spikes. In addition to MRI, SPECT and PET investigations were performed. Electrical activity subsequent to the activity of the epileptic focus could be localized by the MEG after noise reduction using a temporal correlation technique. Simultaneous registration of the magnetic field and the electrical field showed that the source of the primary focal epileptic activity (first period during the total spike wave complex where a dipolar magnetic field pattern is found) is localized in neocortical lateral regions, whereas another focal epileptic activity in a later phase of propagation occurs in temporal mesial regions. In 1 patient (case 1) the primary focal epileptic activity was localized in the surrounding neocortical tissue of an angioma and the middle and inferior temporal gyrus. The second phase of propagation is localized in temporo-basal-mesial regions, including para- and hippocampal structures. The latest center of activity occurred in posterior parts of the gyrus cinguli. In 2 other patients, the primary focal epileptogenic activity was localized at the insula and also spread into temporal basal mesial regions. A multi-modal approach to research of focal epilepsy, combining metabolic, electrical potential, magnetoencephalographic and morphological data, recorded by non-invasive techniques, offers new perspectives for the detection of involved brain regions. The 3-D and time-resolved localization of focal epileptic activity, correlated with the individual anatomy of the human brain, may improve the determination of neuronal populations involved in the individual epileptogenic process, especially in the interaction between temporal or extratemporal neocortex and limbic system.

Value of HM-PAO SPECT in selective temporal lobe surgery for epilepsy

The purpose of this study was to assess the value of interictal 99mTc-hexamethyl-propylenamine oxime (HM-PAO) single-photon emission computed tomography (SPECT) in the preoperative evaluation of epileptic patients with medically refractory seizures of temporal lobe (TL) origin. For this study, we selected 31 patients, who were preoperatively evaluated according to the Zürich presurgical protocol. All patients underwent selective amygdalohippocampectomy. Their surgery was based on ictal and interictal EEG recordings, using scalp and foramen ovale electrodes simultaneously. Postoperatively, 27 patients (87%) were seizure-free or had more than a 90% seizure reduction. All patients had preoperative interictal SPECT and magnetic resonance imaging (MRI) performed. Postoperative SPECT was performed in 18 patients. Preoperative MRI showed structural lesions in 20 cases, and 23 patients had abnormal histopathological findings. Preoperative SPECT determined correctly the primary epileptogenic area in 15 cases (48%), showing a zone of hypoperfusion restricted either to the TL (n = 9; 29%) or exceeding the TL structures (n = 6; 19%). In two patients (6%), the SPECT findings were located contralateral to the affected TL, and in one (3%) there was reduced regional cerebral blood flow in the ipsilateral basal ganglia. Thirteen patients (42%) had normal SPECT. No significant correlations were found among preoperative SPECT findings, MRI and histopathological results, and the postoperative clinical outcome. Based on the results of this study, we regard HM-PAO SPECT to be a useful confirmatory diagnostic tool in presurgical evaluation of epileptic patients. Given the present technological level, it cannot, however, replace the semi-invasive EEG methods.

P180 Telemetry recording with foramen ovale electrodes: A series of 100

P180 Telemetry recording with foramen ovale electrodes: A series of 100

Surgical Treatment of Epilepsy: Initial Results Based Upon Epidural Electroencephalographic Recordings

We describe our initial results in 50 consecutive patients who had investigation for possible surgical treatment of intractable focal epilepsy. Forty-three were investigated using intracranial epidural or foramen ovale electrodes. Forty-five had cortical resection (43 temporal, one frontal, and one parietal). Thirty-two patients who had resection have been followed up for 6 months to 4 years, and 29 (90%) have had good results. Our findings suggest that epidural recordings are valuable in patients with epilepsy who are being considered for surgical resection. They offer an alternative to depth intracerebral investigations in the majority of patients.