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.     

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.     

Detection of temporal lobe spikes: Comparing nasopharyngeal, cheek and anterior temporal electrodes to simultaneous subdural recordings

OBJECTIVE: To compare nasopharyngeal (NP), cheek and anterior temporal (AT) electrodes for the detection yield and localization of interictal spikes in temporal lobe epilepsy. METHODS: In patients evaluated for epilepsy surgery with subdural electrocorticography electrodes, we simultaneously recorded NP, cheek and AT electrodes. Two observers identified spikes in EEG traces and marked in which channels they occurred. Interobserver agreement was calculated using Cohen's kappa. For localization, data-sets with high interobserver agreement (kappa-value 0.4) were evaluated. The subdural distribution of NP and AT spikes was mapped. RESULTS: Seven patients were included, six were analyzed for localization. Only 1.5% of spikes recorded by cheek electrodes were not seen on temporal leads, while 25% of NP spikes were not seen on either. Spikes only recorded by NP electrodes had mesiobasal, while AT spikes had lateral temporal distribution. CONCLUSIONS: NP electrodes can increase EEG spike detection rate in temporal lobe epilepsy and are more useful than cheek electrodes. Spikes that are seen only on NP electrodes tend to be mesiobasal temporal lobe spikes. SIGNIFICANCE: Adding NP electrodes to scalp EEG can aid interictal spike detection and source localization, especially in short recordings like MEG-EEG.     

The localizing yield of sphenoidal and anterior temporal electrodes in ictal recordings: a comparison study

PURPOSE: To compare the localizing yield of sphenoidal electrodes placed under fluoroscopic guidance (SEs) and anterior temporal electrodes (ATEs) in ictal recordings from a group of patients with seizure disorders of anterior temporal origin. METHODS: We compared ictal recordings of 156 seizures obtained with SEs and ATEs from 40 consecutive patients with seizures of anterior temporal origin. Four electroencephalographers reviewed ictal recordings independently and blind to the patients' identity, presurgical data, and inclusion of ATEs or SEs. Outcome variables included (a) number of correctly localized seizures with SE and ATE recordings by at least three raters; (b) number of ictal foci in which all seizures were localized only with SEs; and (c) number of seizures in which SEs identified the ictal onset > or =5 s earlier than ATEs. RESULTS: Interrater agreement among the four raters was significantly greater with SE than with ATE recordings (p < 0.0001). The number of seizures correctly localized was significantly greater with SEs (n = 144) than with ATEs (n = 99; p < 0.0001). All the seizures [n = 36 (23%)] originating from 14 ictal foci (29%) in 11 patients (27.5%) were localized only with SEs. Finally, the ictal onset was detected at SEs > or =5 s earlier than at ATEs in 67 (43%) seizures originating from 33 (69%) foci in 30 (75%) patients. CONCLUSIONS: SEs improve interrater agreement in the localization of seizures of anterior temporal origin, and in about one fourth of patients, SEs add ictal data not identified by ATEs.     

Electrophysiologic investigation of the anterior temporal and frontal lobes: sphenoidal and intraorbital electrodes

The authors have evaluated the interest of sphenoidal electrodes in detection of internal temporal spikes, and intra-orbital electrodes in the detection of orbito-frontal spikes. From a study of 26 patients, 21 with sphenoidal electrodes, 3 with intra-orbital electrodes and 2 with both electrodes, they observed the sensitivity and specificity of such electrodes in detecting spikes with no traduction upon extra-cranial electrodes, or with an unsuspected traduction as spikes at a distance from deep electrodes, or spikes on 2 foci, or bisynchronous discharges. Sphenoidal and intra-oribital electrodes constitute a non-invasive method that provides excellent information in the exploration of the mesiobasal cerebral face. Indications for the use of such a method are complex absences without EEG traduction or with an unsuspected traduction and without abnormalities on CT scan, in the context of functional surgery of epilepsy.     

Standard sphenoidal and mini-sphenoidal electrodes: A direct comparison

This study was designed to directly compare EEG recordings from standard sphenoidal (SS) electrodes to those obtained from subdermal “mini-sphenoidal” (MSP) electrodes. A montage was designed to include SS electrodes, MSP electrodes, and surface temporal leads. In a series of 100 consecutive patients, 9 cases demonstrated abnormalities in the SS and MSP electrodes only. An additional 6 patients had abnormalities present only in the SS electrodes. We conclude that MSP electrodes cannot be substituted for SS electrodes in the search for suspected abnormalities in temporal, inferior, or mesial brain regions.     

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.     

Correlation between inter-ictal regional cerebral blood flow and sphenoidal electrodes - recorded inter-ictal spikes in mesial temporal lobe epilepsy

Abstract

The objective of this study was to assess the reliability of the diagnosis of mesial temporal lobe epilepsy using EEG and sphenoidal electrodes. Inter-ictal 99 m Tc-HMPAO SPECT scans were registered in 21 patients with confirmed mesial temporal lobe epilepsy identified by scalp EEG and sphenoidal electrodes. Visual and quantitative SPECT analysis was performed blind to EEG data. An asymmetry index (Al) was measured from the ratio of two symmetrical regions of interest. A temporal lobe hypoperfusion was defined as an uptake reduced by 5% with respect to the contralateral region. Inter-ictal SPECT abnormalities were observed in 12 out of 21 patients (57%) from both visual and quantitative analysis (focal hypoperfusion in 11 cases, focal hyperperfusion in one case). In seven patients (33%) both visual and quantitative scintigraphy were normal. Abnormal Al was found in 11/15 patients with a high frequency of seizures and in 1/6 patients with a low frequency of seizures. The major data is that the probability to have an abnormal SPECT is statistically correlated to the frequency of the epileptic fits. The couple EEG recordings with sphenoidal electrodes and SPECT is sensitive and reliable in the diagnosis of mesial temporal lobe epilepsy. [Neurol Res 2000; 22: 674-678]     

Relative utility of sphenoidal and temporal surface electrodes for localization of ictal onset in temporal lobe epilepsy.

OBJECTIVES: To compare localization of ictal onsets in patients with possible temporal lobe epilepsy (TLE) using true temporal electrodes (TE), at positions T1 and T2, and sphenoidal electrodes (SpE). METHODS: A total of 101 ictal tracings in 31 patients with possible TLE were independently reviewed by two readers and graded as meeting (TE+, SpE+) or not meeting (TE-, SpE-) strictly-defined mesial temporal onset criteria. TE and SpE were reviewed in separate montages, with ad lib adjustment of filters and sensitivity. Discrepancies between TE and SpE were noted, with inter-reader disagreements resolved by a third reviewer. RESULTS: All seizures scored as SpE+ were also scored as TE+, with one exception. The sole SpE+/TE- seizure did not add incremental useful information in that patient, who had other, similar seizures which were TE+. Five seizures in 4 patients were scored as TE+ and SpE-, most due malfunction of SpE prior to seizure onset. One of these seizures was scored TE+/SpE- in a patient believed to have neocortical epilepsy. CONCLUSIONS: In this series, SpE were unnecessary to detect seizures which meet strict mesial temporal onset criteria and did not yield useful information for surgical evaluation beyond that provided by TE. It remains unclear if SpE are more helpful than TE in distinguishing lateral from mesial ictal onset. Digital review of ictal tracings may resolve discrepancies between TE and SpE.     

Ictal recordings of ambulatory cassette EEG with sphenoidal electrodes in temporal lobe epilepsy: comparison with intensive videomonitoring

Seventy-three seizures in 18 epilepsy patients were studied by analyzing the ictal findings of 8-channel ambulatory EEG (A/EEG) and adjacent 16-channel intensive videomonitoring (IVM). With IVM and A/EEG analysis, accuracy was excellent for determining the lateralization of seizure progression; whereas at seizure onset and post-ictal slowing, accuracy was poor. No false lateralization was found in A/EEG compared with IVM or lateralization according to patient data, and in seizure lateralization the interpretation of A/EEG was discordant in only 3 seizures with IVM analysis. According to our study, ictal 8-channel A/EEG with sphenoidal electrodes is not suitable for localization of temporal lobe foci, but is reliable for lateralization analysis.     

The necessity for sphenoidal electrodes in the presurgical evaluation of temporal lobe epilepsy: con position.

This article reviews several lines of evidence that efface the requirement for sphenoidal leads in the EEG investigation of temporal lobe epilepsy. Mandibular notch or anterior temporal electrodes, each situated well within the anterior temporal spike field, detect interictal and ictal epileptiform phenomena virtually as well as do sphenoidal leads, provide consistent recording circumstances, do not require physician expertise for their placement, and create no discomfort. This article also cites many studies demonstrating the reliability of ictal semeiology and of MRI in lateralizing and localizing temporal epileptogenesis. Thus, EEG constitutes one element in a matrix of lateralizing data.     

The necessity for sphenoidal electrodes in the presurgical evaluation of temporal lobe epilepsy: pro position.

Whether sphenoidal electrodes should be used in the presurgical evaluation of people with refractory epilepsy has remained controversial. Many studies have been published touting their advantages, or conversely, their lack of benefit. The present paper reviews the evidence supporting the utility of sphenoidal electrodes. In principle, sphenoidal electrodes have an advantage over laterally placed scalp electrodes in detecting inferiorly directed mesial temporal discharges. Published studies demonstrate that sphenoidal electrodes are more sensitive than scalp electrodes and sometimes detect interictal spikes and seizures not seen with scalp electrodes. While the net added yield is relatively low, perhaps 5 to 10%, those patients in whom sphenoidal electrodes provide unique localizing information have much to gain. Sphenoidal electrodes may spare some patients unnecessary intracranial electrode investigation and permit surgery for others.     

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.     

长程蝶骨电极脑电图对颞叶痫灶的定位价值探讨

目的 探讨长程蝶骨电极脑电图对颞叶痫灶的定位价值.方法 回顾性分析经手术治疗的119例颞叶癫痫患者,将其术前的常规脑电图 蝶骨电极(以下简称常规蝶骨电极)与视频脑电图 长程蝶骨电极脑电图(以下简称长程蝶骨电极)检测结果进行分析,其定位结果与术中描记的皮层脑电图(ECoG)及深部脑电图(DEEG)结果进行比较.结果 痫样放电在常规蝶骨电极和长程蝶骨电极的总检出率分别为68.9%和94.1%;其定侧率各为67.1%和99.1%(P＜0.005).术中脑电图证实了术前的长程蝶骨电极脑电图定位准确率高,DEEG与长程蝶骨电极定位吻合率达98.2%.本组随访1～5年,总有效率为97.4%,效果优良为88.6%.结论 长程蝶骨电极对颞叶痫样放电的检出和定侧率高,且准确率高.准确定位可提高手术疗效.     

Comparison of sphenoidal, foramen ovale and anterior temporal placements for detecting interictal epileptiform discharges in presurgical assessment for temporal lobe epilepsy.

OBJECTIVES: Some authors have recently stressed that the position of the tip of the sphenoidal electrode plays a crucial role in its efficacy to detect mesio-basal spikes. We have tested this hypothesis by comparing the sensitivity of a contact of a foramen ovale bundle located at the foramen ovale (CFO) with scalp electrodes in detecting interictal epileptiform discharges. We have also compared deep and superficial foramen ovale contacts in the same bundle in order to establish whether deeper contacts can detect epileptiform discharges not seen at the foramen ovale or on the scalp. METHODS: The sensitivity for detecting epileptiform discharges of simultaneous intracranial and scalp EEG recordings from 20 patients under telemetric presurgical assessment for temporal lobe epilepsy were compared. RESULTS: Out of 2280 epileptiform discharges evaluated, about 70% were seen only at the deep foramen ovale contacts. Out of the 722 discharges recorded by CFO and/or scalp electrodes, 698 were seen at the CFO and 690 at the scalp anterior temporal electrode. Only on 29 occasions (4.15%) were discharges recorded at the CFO and not at the anterior temporal electrode. On 21 occasions (3.04%) CFO failed to detect discharges seen at the anterior temporal electrode. CONCLUSIONS: Our findings confirm previous results suggesting that sphenoidal electrodes, however accurately positioned, offer no significant increase in detection sensitivity compared with anterior temporal scalp electrodes. In addition, these results confirm that a large proportion of discharges seen at the deepest foramen ovale contacts are not seen either on the scalp nor at the superficial foramen ovale contacts.     

Electroencephalographic recording from the temporal lobes: a comparison of ear, anterior temporal, and nasopharyngeal electrodes

A prospective study was performed to evaluate the usefulness of ear, anterior temporal, and nasopharyngeal electrodes for recognizing temporal lobe epileptic electroencephalographic (EEG) foci. One hundred and three EEGs were performed on patients suspected of having epilepsy who had a previous normal record. Nasopharyngeal electrodes were simultaneously compared with ear and anterior temporal electrodes to determine their relative abilities to detect pathological epileptiform transients from the temporal region. Epileptic discharges were detected in 22% of the recordings. Pathological discharges seen in nasopharyngeal electrode derivations invariably were seen in ear and anterior temporal electrode derivations using carefully designed montages, and EEG diagnosis was not altered by use of nasopharyngeal electrodes. We conclude that EEG recording with ear and anterior temporal electrodes is sufficient to detect pathological temporal epileptiform transients, and that the use of nasopharyngeal electrodes as a routine procedure offers no added benefit.     

Convulsive syncope following placement of sphenoidal electrodes.

Two cases of convulsive syncope following the insertion of sphenoidal electrodes are reported. The episodes occurred shortly after an uneventful insertion of the needle. Both patients exhibited behavioral arrest with loss of muscle tone, followed by flexor posturing, jerking of the extremities, then followed by what appeared to be a panic attack. Episodes were clinically distinct from the patients' typical spells and were initially interpreted as representing psychogenic events. EEGs during the episodes showed diffuse slowing followed by generalized suppression of rhythms. Simultaneous EKG showed bradycardia followed by brief asystole and then resumption of normal heart rhythms in both cases. Vagally mediated cardioinhibitory reactions induced by fear, pain and possibly stimulation of branches of the trigeminal nerve in the face represent an uncommon but potentially serious complication of placement of sphenoidal electrodes.