A simultaneous comparison of acupuncture needle and insulated needle sphenoidal electrodes for detection of anterior temporal spikes.

Uninsulated acupuncture needles have been used as sphenoidal electrodes, but the issue of insulation has not been adequately addressed. In this report, acupuncture needles and insulated needle sphenoidal electrodes were simultaneously used to compare the rate of spike detection, spike amplitude and distribution of maximal spikes from eight spike foci in seven patients with temporal lobe epilepsy. When compared to the insulated needle electrode, the acupuncture needle electrode was equally effective in spike detection, but spike amplitudes tended to be smaller and maximal spikes were less frequently encountered. Thus, insulation has an influence on the spikes recorded by the acupuncture needle sphenoidal electrode. However, the overall effect appears to be not sufficiently different from the insulated needle electrode for the purpose of detecting anterior temporal spikes in outpatient EEG recordings for the diagnosis of temporal lobe epilepsy.     

Multiple electrodes for detecting spikes in partial complex seizures

The contribution of various electroencephalographic electrodes in detecting spikes from patients with seizures of suspected anterior temporal origin was prospectively studied with a standard protocol. The following electrodes were studied: International Standard 10-20 positions F7-8 and A1-2, sphenoidal (SP), nasopharyngeal (NP), anterior temporal (T1-2), mandibular notch surface (MNS), and mandibular notch subdermal (MNSD). Twenty patients were recorded of whom 16 demonstrated anterior temporal spikes. There was no difference in the number of spikes detected by SP, MNS, MNSD, or T1-2 electrodes (p less than 0.05); however these electrodes detected significantly more spikes than NP, F7-8, or A1-2. The SP electrode recorded spikes of highest amplitude (p less than 0.05). We conclude that for patients suspected of having seizures of anterior temporal origin, (1) a substantial number of spikes will be missed if only the International Standard electrode system is employed; (2) in comparison to SP electrodes the non-invasive and easily applied MNS or T1-2 electrodes will detect almost all spikes and should be used in outpatient EEG recordings; (3) NP electrodes provide no information that cannot be obtained by more reliable and better tolerated electrodes.     

Surface sphenoidal electrode for recording anterior temporal spikes.

Spike analysis was performed to determine if surface sphenoidal electrodes were suitable substitutes for depth sphenoidal or anterior temporal electrodes in outpatient EEG recordings for the diagnosis of complex partial seizures of anterior temporal origin. Spike measurements consisted of spike detection rate, spike amplitude, and location of maximal amplitude spikes. Depth sphenoidal electrodes had the highest yield in these three measurements. Surface sphenoidal electrodes did not differ from anterior temporal electrodes in spike detection rate and spike amplitude, but the former recorded almost no maximal amplitude spikes, while the latter had approximately 30% of the maximal spikes. It is concluded that surface sphenoidal electrodes are slightly inferior to anterior temporal electrodes, but the differences between them are minimal for practical purposes in outpatient EEG recordings.     

Long-Term Ambulatory Cassette EEG with Sphenoidal Recording in Complex Partial Seizures

Long-term ambulatory cassette EEG with sphenoidal recording (A/EEG-SP) was performed in 51 patients. Group A comprised 31 patients with a clinical diagnosis of complex partial seizures (CPS), and group B comprised 20 patients suspected of having CPS. In group A, detection of temporal spikes was 27% by routine EEG (R/EEG), 72% by sphenoidal EEG (SP/EEG), 27% by A/EEG with temporal chain montage, and 91% by A/EEG-SP. The highest yield achieved by A/EEG-SP as compared with other EEG recordings was documentation of spontaneous seizures of temporal lobe origin. The detection rate of spontaneous seizures by A/EEG-SP was approximately 30%, and the focal or regional onset of seizures could be determined in 60% of patients. In group B, detection of temporal spikes was 11% by R/EEG, 18% by SP/EEG, and 30% by A/EEG-SP. Spontaneous seizures were recorded by A/EEG-SP in two patients (10%). Thus, A/EEG-SP was more effective than A/EEG in detecting interictal and ictal temporal discharges, and A/EEG-SP was superior to SP/EEG in documenting spontaneous seizures of temporal lobe origin.     

Significance of Simple Partial Seizures in Temporal Lobe Epilepsy

Summary: We determined how localization of simple partial seizures (SPS) correlated with localization of complex partial seizure (CPS) in scalp/sphenoidal EEG and assessed prognosis after temporal lobe resective surgery in patients with an ictal correlate of SPS in scalp/sphenoidal EEG recordings. EEGs were recorded with the 10–20 system of electrode placement and supplemented with sphenoidal electrodes. Between 1985 and 1992, 183 patients with temporal lobe epilepsy (TLE) reported an aura (SPS) during inpatient monitoring; all were eligible for inclusion in our study. The EEGs during SPS showed ictal changes in 51 patients (28%, 117 SPS). Forty-four patients had unilateral temporal interictal spikes (IIS), and SPS and CPS always arose from the same region. Seven patients had bitemporal interictal spikes; SPS colocalized with CPS in 4 patients (57%), SPS were contralateral to CPS in 2 patients, and 1 patient had bilateral independent CPS but unilateral SPS. SPS accompanied by EEG ictal changes conveyed a favorable prognosis in patients who underwent epilepsy surgery. Scalp/sphenoidal recorded IIS but were less reliable in identifying the location of CPS onset in patients with bitemporal spikes.     

New sphenoidal electrode assembly to permit long-term monitoring of the patient's ictal or interictal EEG.

A new sphenoidal wire electrode is described which greatly increases the clinical and diagnostic usefulness of sphenoidal electrode recordings. These very fine wire electrodes are easy to insert; they are comfortable and acceptable to the patient. In contrast to sphenoidal needle electrodes they expose the patient to no risk should he have a seizure during recording. These electrodes also allow one to extend the recording time to several days, thus increasing the chances of recording a spontaneous seizure, for instance while the patient's EEG is being recorded with a telemetry system. The extended recording time also allows for continuous automatic sampling of the interictal EEG over a period of several days. The quality and the reliability of the EEG record are also enhanced. The new sphenoidal electrodes have been used on over 100 patients and are now being used routinely on suspected temporal lobe epileptics recorded with conventional techniques, while 50 of the patients have also been recorded with a cable-telemetry seizure monitoring system which has captured 65 spontaneous seizures.     

Sphenoidal electrodes THEIR USE AND VALUE IN THE ELECTROENCEPHALOGRAPHIC INVESTIGATION OF COMPLEX PARTIAL EPILEPSY

The diagnostic value of sphenoidal electrode EEG recordings in patients with seizures characteristic for epilepsy with complex partial symptomatology was assessed in a study comprising 404 patients; 71.3% of the patients had seizures with automatisms and amnesia, and 28.7% had psychic seizures with subjective phenomena such as hallucinations and illusions. A total of 59.6% of the patients had diagnostic EEG changes in routine waking or sleep EEG. In sphenoidal EEG recording including thiopenthone activation, diagnostic changes were found in 40.5% of the patients without specific changes in waking or sleep EEG, the chance of a positive finding being more than five times higher in patients with automatisms than patients with psychic seizures. Apart from cases where surgical treatment of temporal lobe epilepsy is considered, sphenoidal electrode EEG recording, including intravenous thiopenthone activation, should be performed in patients with seizure phenomena raising suspicion of epilepsy with complex partial symptomatology but where waking and sleep EEGs fail to demonstrate specific abnormalities.     

Sphenoidal EEG recording in complex partial seizures

A prospective study was performed to evaluate the usefulness of sphenoidal EEG recording during wakefulness, as compared to routine tracings awake and asleep, for recognizing epileptic electroencephalographic foci in patients with complex partial seizures. Fifty patients were investigated. Following sleep deprivation a routine waking EEG, a sleep tracing and an awake recording with sphenoidal needles were obtained. In nine patients temporal epileptiform activity was apparent in all three conditions (wakefulness, sleep and with sphenoidal electrodes). In 21 patients temporal epileptiform activity was seen during sleep only, while the sphenoidal leads were non-contributory. In 20 patients epileptiform activity was not recorded under any of the above conditions. This study indicates that sphenoidal recording during wakefulness does not contribute to the detection of epileptic discharges in patients with complex partial seizures.     

Comparison and correlation of surface and sphenoidal electrodes with simultaneous intracranial recording: an interictal study.

We prospectively compared and correlated interictal spikes recorded with simultaneous surface, sphenoidal, depth and subdural electrodes in 21 patients. Although the amplitude of sphenoidal spikes was often larger than that of surface spikes in patients with mesial basal temporal ictal and interictal foci, only 1 patient had exclusively sphenoidal spikes. Spikes with maximal amplitude at the sphenoidal electrode arose from mesial temporal, temporal neocortical and orbital frontal foci. An inferior vertical temporal dipole (hippocampal positive and inferior temporal neocortex negative) was associated with surface and sphenoidal spikes.     

Effect of barbiturate on epileptiform activity: comparison between intravenous and oral administration

The present study was performed in order to compare: 1) the differences between oral and intravenous barbiturate on interictal epileptiform activity (sharp-waves and spikes) in the EEG, and 2) interictal epileptiform activity in the sphenoidal electrode compared to the temporal and zygomatic electrodes (an electrode placed at the cutaneous entry of the sphenoidal electrode) during intravenous barbiturate administration in patients with epilepsy. Two procedures were performed: 1) an oral pentobarbital sleep induction with 10–20 electrode placement including a zygomatic electrode, and 2) an intravenous thiopental sleep induction with the same electrode placement including a sphenoidal electrode. Thirty eight patients with complex partial seizures were included. During the oral pentobarbital procedure 34 of 38 (90%) patients showed interictal epileptiform activity compared with 22 of 38 (55%) patients during the intravenous thiopental procedure (p<0.005). A interictal epileptiform focus was observed in 33 (87%) patients in the oral procedure and in 19 (50%) patients in the intravenous procedure (p<0.01). Interictal epileptiform activity recorded in the sphenoidal electrode was also recorded in the zygomatic electrode. Except from two patients a good correlation was observed between the zygomatic electrodes and the F7/F8 electrodes. We conclude that administration of intravenous thiopental offers no advantage compared to the administration of oral pentobarbital as an activating procedure, and for standard interictal EEG recordings with sleep activation procedures, suitable places scalp electrodes including a zygomatic electrode with the use of oral pentobarbital may be sufficient.     

Combined use of sphenoidal electrodes and the dipole localization method for the identification of the mesial temporal focus

We attempted to sub-classify four cases who show temporal spikes on standard scalp electroencephalogram (EEG), using sphenoidal electrodes and the dipole localization METHOD: In a case with mesial temporal epilepsy, spikes showed phase reversal in a sphenoidal electrode, and the spike dipoles were estimated to be in the mesial temporal lobe. In a case with lateral temporal epilepsy, spikes showed no phase reversal in a sphenoidal electrode, and the spike dipoles were estimated to be in the lateral temporal lobe. In two cases out of four, spikes showed phase reversal in sphenoidal electrodes, whilst the dipoles were estimated to be in the frontal lobe. Clinical features also suggested a diagnosis of frontal lobe epilepsy. In one of the two cases in which frontal lobe epilepsy was suspected, ictal dipoles as well as interictal spike dipoles indicated participation of the frontal lobe in the genesis of seizures. Nevertheless, only mesial temporal lobectomy was performed based on results obtained by invasive subdural electrodes. As a result, seizures were not controlled. Although sphenoidal electrodes were useful for differentiating between mesial and lateral temporal lobe foci, it is advisable to use them in combination with the dipole localization method to identify frontal lobe foci.     

Conditions for Omitting Invasive Long-Term Monitoring before Surgical Resection in Patients with Temporal Lobe Epilepsy

Abstract: The omission of invasive long-term monitoring before surgical resection in patients with epilepsy should be permitted only for those in whom the epileptogenic focus is presumed to localize unilaterally in the mesial aspect of the temporal lobe. The localization may well be confirmed through noninvasive measures. Retrospective analyses of data obtained from noninvasive investigations (scalp-recorded and sphenoidal EEG, neu-rolmages, and electroclinical seizure manifestations) were carried out in 58 :patients. The localization of their epileptogenic focus was subsequently confirmed by the implantation of both intracerebral and subdural electrodes; the focus had an amygdalohippocampal origin in 41 :patients and a lateral temporal origin in 17 :patients. From the comparison of noninvasive Andings between these two groups, we propose the following indispensable conditions for omitting an invasive evaluation: 1. Appearance of focal epileptic discharges unilaterally in the sphenoidal lead observed during the simple phase of partial seizures, or unilateral discharges with predominancy in the sphenoidal lead during the early phase of complex partial seizures. 2. Interictal spikes on scalp-recorded EECs localizing unilaterally in the anterior region of the temporal lobe, and if bilaterally independent, presenting with unilateral predominancy in a ratio of greater than 41. 3. Presence of autonomic signs in the initial phase of signal symptoms. 4. Neuroimaging Andings in the mesial temporal region: elongated T2 on MRI and hippocampal atrophy, or a tumorous lesion. The lateralhation conforms to interictal and ictal paroxysmal EEC findings. There were 8 :patients with seizures of amygdalohippocampal origin who satisfied all the indispensable condition, but not a single patient with seizures of lateral temporal origin. Thus, the conditions we propose are surely useful for determining whether patienta with lateral temporal seizures should be excluded from invasive long-term monitoring before surgical resection.     

Comparison of coronal sphenoidal versus standard anteroposterior temporal montage in the EEG recording of temporal lobe seizures

Chronic sphenoidal electrodes were developed to facilitate the recording and localization of temporal lobe seizures during long term monitoring. Many reports demonstrate their utility in displaying temporal iterictal epileptiform activity, but there have been few direct comparisons of sphenoidal electrodes and surface temporal recordings ictally. We compared simultaneous portions of 74 EEG recordings of temporal lobe seizures (from 42 patients), with one portion including sphenoidal electrodes in a coronal montage and one with a standard anterior posterior temporal montage. Separated tracings were reviewed by readers blinded to the other portion of the tracing. The coronal sphenoidal montage allowed recognition of temporal lobe seizures inapparent with standard surface temporal electrodes in 19% of seizures and led to an earlier identification (usually by ≥5 s) ofthe onset in 70% of seizures. Indwelling, flexible sphenoidal electrodes assist in ambulatory recording of temporal lobe seizures, both in demonstrating the presence of seizures and in determining the localization and time of seizure onset.     

New-onset mesial temporal lobe epilepsy in a 90-year-old: clinical and EEG features

Although there is a peak in the incidence of epilepsy in the elderly compared with the general population, complex partial seizures represent less than 15% of the seizure types reported. We report on a 92-year-old woman with a 2-year history of daily complex partial seizures. Prolonged video/EEG recording showed bilateral anterior mesial temporal interictal spikes, which predominated on the left, and two typical seizures arising from the left temporal area. Cranial MRI scanning showed multiple lacunar infarcts without temporal lobe involvement or mesial temporal atrophy. Our case appears to be oldest patient in the literature with newly diagnosed mesial temporal lobe epilepsy confirmed by video/EEG recording.     

Sphenoidal electrode insertion under local analgesia in children

The indications for method and the results of sphenoidal electrode insertion under local analgesia are evaluated in children. This technique makes it possible to study the hippocampal area, which cannot be studied by other extracranial electrodes. It also localizes in a temporal lobe some complex seizures without electrical events on surface recordings, complex sezures with bilateral temporal spikes or a frontotemporal focus of spikes, as well as those with a temporal focus with bilateral synchronous spikes in standard EEG. Therefore, sphenoidal electrodes inserted without heavy general analgesia enable temporal seizures to be identified and localized, leading to more specific neuroradiological and neurophysiological explorations and helping in this way to select possible patients for epileptic surgery.     

Mesial temporal spikes: a simultaneous comparison of sphenoidal, nasopharyngeal, and ear electrodes

A prospective study was performed to compare the relative ability of sphenoidal (SP), nasopharyngeal (NP), and ear electrodes for detecting mesial temporal lobe epileptiform discharges. Forty-four EEGs were performed on patients with complex partial seizures, simultaneously recording from NP, SP, and ear electrodes. Spikes were noted in SP derivations in 25 records, in ear derivations in 23 records, and in NP derivations in 20 records. A total of 875 spikes were counted, SP showing 99%, NP 57%, and ear 54% of discharges, with greatest amplitudes generally seen in SP derivations. The Mann-Whitney rank sum test showed SP electrodes superior to both NP and ear electrodes (p less than 0.0001) and no significant differences between NP and ear electrodes. We conclude that SP electrodes are superior to both NP and ear electrodes in detecting mesial temporal spikes.     

Psychomotor epilepsy and psychosis

The EEG findings in waking, sleep, and sphenoidal electrode recordings in 96 patients with partial epileptic seizures with complex symptoms, who, after a median interval of 18 years developed paranoid/hallucinatory psychosis, were compared with the findings from a group of patients without psychosis, who had had the same type of epilepsy in median 24 years. There were no significant differences between the two groups with regard to median age at onset of epilepsy or complex partial seizures, age, or duration of epilepsy at time of examination. the psychotic patients had a significant preponderance of temporal medio-basal spike foci, recorded on the sphenoidal electrode, indicating deep temporal lobe dysfunction as an important factor in the pathogenesis of psychosis. A significant higher frequency of bilateral and multiple spike foci, together with a significant frequency of slow-wave admixture to the waking background EEG activity, indicated more extensive and severe epileptogenic lesions in the psychotic patients. There was no correlation between psychosis and unilateral EEG foci in either temporal lobe.     

Sensitivity of recordings at sphenoidal electrode site for detecting seizure onset: evidence from scalp, superficial and deep foramen ovale recordings.

OBJECTIVES: Some authors have recently stressed that the position of the tip of sphenoidal electrodes plays a crucial role in their efficacy in detecting ictal onset. An opportunity to test this hypothesis is provided by recordings from the most superficial contacts of foramen ovale (FO) electrode bundles because these contacts are located at the FO, in a position equivalent to that of optimally located sphenoidal electrodes. To simplify wording, recordings obtained by superficial FO electrodes will hereafter be called sphenoidal recordings, although they have not been obtained with standard sphenoidal electrodes. The sensitivities of simultaneous scalp and sphenoidal recordings for detecting ictal onset have been compared with each other, and with a 'gold standard' provided by simultaneous deep intracranial FO recordings from the mesial aspect of the temporal lobe. METHODS: Three hundred and fourteen seizures obtained from 110 patients under telemetric presurgical assessment for temporal lobe epilepsy have been studied. Scalp electrodes included anterior temporal placements. All scalp electrodes were considered when identifying seizure onset but the anterior temporal electrodes were most frequently involved. RESULTS: Ictal onset time at sphenoidal and scalp recordings: initial ictal changes appeared simultaneously in scalp and sphenoidal recordings in 123 seizures (39.2%). Initial changes occurred earlier in sphenoidal recordings in 63 seizures (20.1%), whereas they were seen earlier on the scalp in 76 seizures (24.2%). Artefacts prevented the comparison between sphenoidal and scalp recordings in 16 seizures (5.1%) and no ictal changes were seen on the scalp and/or sphenoidal recordings in 36 seizures (11.5%). In most of the 63 seizures where ictal changes appeared earlier in sphenoidal recordings, a delayed ipsilateral scalp onset was seen as the signal amplitude increased or scalp changes could be identified retrospectively on the scalp with an onset which appeared simultaneous and ipsilateral to the initial sphenoidal changes. Sphenoidal recordings supplied additional information when compared to scalp recordings in only 22 seizures (7%): in 5 seizures with artefacts on the scalp, in 6 seizures with no changes on the scalp and in 11 seizures with discrepant laterality at onset. Congruence in laterality with respect to deep intracraneal FO recordings: of the 61 seizures with unilateral onset on the scalp, onsets at sphenoidal recordings and deep FO electrodes were ipsilateral in most cases. In only 3 of these 61 seizures (4.9%), sphenoidal recordings lateralized ipsilateral to the deep FO electrodes in the presence of a contralateral onset on the scalp. In 14 among the 122 seizures (11.5%) with bilateral asymmetrical onset on the scalp, sphenoidal recordings lateralized seizure onset ipsilateral to the deep FO electrodes in the presence of a contralateral scalp onset. Thus, when compared with scalp EEG, sphenoidal recordings increased laterality congruence with respect to deep FO electrodes in 17 seizures (5.4%). CONCLUSIONS: Extracranial electrodes located next to the FO at the sphenoidal electrode site yield an improvement over suitable surface electrodes in the identification of ictal onset in only 5.4-7% of seizures. Such improvement derives from the fact that the low amplitude signals often seen at seizure onset may show higher amplitude on sphenoidal than on scalp recordings.     

Distribution of temporal spikes in relation to the sphenoidal electrode

Sphenoidal EEG recordings were performed in 111 patients with epilepsy, who showed antero-mesial temporal epileptiform discharges. In 6, a multipolar sphenoidal electrode showed a shallow potential gradient between the standard sphenoidal site and the surface. In 17 patients a superficial electrode at the site of entry of the sphenoidal wire recorded all discharges seen at the sphenoidal. Out of 165 foci, in only 2 instances were less than 90% of sphenoidal discharges recognisable on the surface. In 39 patients who underwent surgery, lesions confined to mesial temporal structures were found to be associated with inter-ictal discharges maximal at the sphenoidal electrode. A mid-temporal maximum was always associated with diffuse non-specific, or lateral temporal pathology. It is concluded that sphenoidal recording offers no advantage over suitably placed scalp contacts for detecting inter-ictal epileptiform discharges. It may be of some value for differentiating between mesial and lateral temporal foci.     

Localization of magnetic interictal discharges in temporal lobe epilepsy

Three young adults with intractable complex partial seizures were studied by electroencephalography, magnetoencephalography, and electrocorticography. Interictal electroencephalographic (EEG) spikes for each patient were grouped according to their morphological characteristics and distribution across channels. Mapping of simultaneously recorded magnetoencephalographic signals produced dipolar patterns from which the three-dimensional locations of equivalent current dipoles were calculated, whereas the mapping of EEG spikes showed single regions of electronegativity. The magnetic spikes were localized to the anterotemporal lobe, and the EEG spikes were localized somewhat anterior or posterior to the magnetic spikes. The magnetoencephalographic findings corresponded well with intraoperative electrocorticographic and depth-electrode findings of discharging areas located over the lateral temporal lobe and on the basal and mesial surfaces of the temporal cortex.