Methohexital (Brevital) Effect on Electrocorticogram May Be Misleading

Intravenous (i.v.) methohexital (MTH, Brevital) was found to have an effect on the intraoperative electrocorticogram (ECOG) of 63 patients who had temporal lobectomies performed under general anesthesia for intractable complex partial seizures. In the preresection ECOG, MTH increased the frequency of spikes in 78%, the area of cortical spiking in 30% and induced seemingly "new" spike foci in 43%. Similar although less dramatic changes occurred in the final (i.e., postresection) ECOG. Whether these changes induced by MTH, specifically the new spike foci, are significant was assessed by correlating surgical results with the presence of "residual spikes" (i.e., after all resections, not spontaneously occurring but activated by MTH). Surprisingly, nine patients with residual "MTH-spikes" did not have any postoperative seizures whereas two had some. This raises the question of whether MTH effects are significant overall. Caution is advised in the use of MTH in intraoperative assessment of interictal spike fields, especially when new spike foci are activated. Further study of the possibility of false activation, with a larger series, is advised.     

The Effects of Remifentanil on Epileptiform Discharges during Intraoperative Electrocorticography in Patients Undergoing Epilepsy Surgery

PURPOSE: High-dose i.v. opioids (e.g., alfentanil, 50 microg/kg bolus) are known to increase the intraoperative reading of epileptiform activity during epilepsy surgery (ES), thereby facilitating localization of the epileptogenic zone (i.e., the site of ictal onset and initial seizure propagation). However, this phenomenon has not been studied with remifentanil (i.e., a novel ultra-short acting opioid). The purpose of the present study was to evaluate the effect of remifentanil on electrocorticography (ECoG) during ES. METHODS: After Institutional Review Board approval, 25 adult patients undergoing elective ECoG-guided anterior temporal corticectomy were enrolled. At the time of ECoG, anesthesia consisted of inhaled isoflurane < or =0.1% (end-tidal) in 50% N2O, and i.v. fentanyl, 2 microg/kg/h and vecuronium. Patients were maintained at normocapnia and normoxia during ECoG. After acquisition of baseline ECoG, bolus remifentanil, 2.5 microg/kg i.v., was administered. The number of epileptiform spikes occurring 5 min before and after this bolus were compared by using a one-sided sign test; p values < or =0.05 were considered statistically significant. RESULTS: When compared with baseline ECoG, bolus i.v. remifentanil significantly increased the frequency of single spikes or repetitive spike bursts in the epileptogenic zone while suppressing activity in surrounding normal brain. CONCLUSIONS: During ES, remifentanil enhanced epileptiform activity during intraoperative ECoG. Such observations facilitate localization of the epileptogenic zone while minimizing resection of nonepileptogenic eloquent brain tissue. Although not specifically evaluated in this study, we speculate that remifentanil's short elimination half-life will facilitate neurologic function testing immediately after ES. Should this be the case, we envision remifentanil has the potential to supplant other opioids (e.g., alfentanil) during ECoG-guided ES.     

Methohexital Activation of Epileptogenic Foci During Acute Electrocorticography

Methohexital was used as an activating agent in 62 patients undergoing focal cortical resections of epileptogenic foci and in six patients undergoing chronic electroencephalogram (EEG)/video monitoring with intracranial strip electrodes. In 87% of cases, methohexital caused selective activation of the epileptogenic focus during acute electrocorticography (ECoG). This activation appeared to be specific for the epileptogenic focus and did not cause epileptiform spiking from adjacent nonepileptogenic cortex. This ECoG activation occurred whether patients received local or general anesthesia. Sixty-five percent of patients demonstrated adequate activation with as little as 25 mg of drug. Methohexital is a safe and reliable method of activating epileptogenic foci during acute ECoG recordings and can decrease the time for ECoG recordings during surgery.     

Effect of Anterior Callosotomy on Bilaterally Synchronous Spike and Wave and Other EEG Discharges

Summary: We analyzed pre- and postoperative interictal and ictal EEG patterns in relation to seizure outcome in 29 patients with intractable epilepsy who had undergone anterior callosotomy. Twenty-two patients had generalized bilaterally synchronous sharp or spike and slow wave discharges (GSW) and 7 did not: Postoperatively, patients with preoperative GSW showed disruption of synchrony, increased amplitude asymmetry, and a decreased amount of GSW. No significant decrease was noted in the amount of total epileptic discharge after operation. There was a significant relation between seizure outcome and decrease in amount of GSW. The degree of disruption of synchrony, total amount of epileptic discharge, and pre- and postoperative EEG patterns were not good indicators of seizure outcome. Postoperative changes in lateralization of epileptic foci consisted either of increased lateralization, less lateralization but increased independent discharges in the previously nonpredominant hemisphere, or appearance of some lateralization. There appears to be a spectrum of GSW: Both sec-ondary bilateral synchrony and secondarily generalized corticoreticular epileptic discharges are distributed along this spectrum.     

Isoflurane anaesthesia in the treatment of convulsive status epilepticus

Summary Status epilepticus may be resistant to intravenous anticonvulsive drugs. In these cases treatment with the inhalation anaesthetic agent isoflurane may be helpful in the further management. We describe a 35-year-old female patient who suffered from status epilepticus with partial seizures. In spite of therapy with benzodiazepine and phenytoin the status evolved into tonic clonic seizures. Treatment with thiopentone sodium did not stop seizure activity. Anaesthesia with isoflurane (dosage up to 1.5 vol.%) carried out twice within 72 h finally led to a termination of status epilepticus. From our own experience and reports in the literature we conclude that general anaesthesia with isoflurane can and should be used in the treatment of severe status epilepticus that does not respond to intravenous anticonvulsive agents.     

Misleading non-epileptic epileptiform activities on intracranial recordings

Numerous non-epileptic physiological electroencephalographic (EEG) patterns morphologically mimic epileptiform activity. However, misleading non-epileptic findings of electrocorticography (ECoG) have not yet been examined in detail. The aim of the present study was to identify non-epileptic epileptiform ECoG findings. We retrospectively reviewed the intracranial recordings of 21 patients with intractable focal epilepsy who became seizure-free after a presurgical evaluation with subdural electrodes following resective surgeries at Sapporo Medical University between January 2014 and December 2018. Morphological epileptiform findings outside epileptogenic areas were judged as non-epileptic and analyzed. Seventeen areas in nine patients exhibited non-epileptic epileptiform activities. These areas were identified in the lateral temporal cortices, basal temporal areas, rolandic areas, and frontal lobe. Morphological patterns were classified into three types: 1) spiky oscillations, 2) isolated spiky activity, and 3) isolated fast activity. The normal cortex may exhibit non-epileptic epileptiform activities. These activities need to be carefully differentiated from real epileptic abnormalities to prevent the mislocalization of epileptogenic areas.     

Prospective use of subtraction ictal SPECT coregistered to MRI (SISCOM) in presurgical evaluation of epilepsy

Purpose: In patients with drug‐refractory focal epilepsy, nonlesional magnetic resonance imaging (MRI) or discordant data of presurgical standard investigations leads to failure generating a sufficient hypothesis for electrode implantation or epilepsy surgery. The seizure‐onset zone can be further investigated by subtraction ictal single‐photon emission computed tomography (SPECT) coregistered to MRI (SISCOM). This is an observational study of a large consecutive cohort of patients undergoing prospective SISCOM to generate hypothesis for electrode implantation or site of epilepsy surgery. Methods: One hundred seventy‐five consecutive patients undergoing presurgical evaluation with either nonlesional MRI or discordant data of standard investigations preventing the generation of hypothesis for seizure onset were evaluated with SISCOM. Results were compared to gold standard for seizure onset detection, either electrocorticography (ECoG) and/or postoperative outcome. Key Findings: One hundred thirty patients had successful SPECT injection. Hypothesis for electrode implantation/site of surgery was generated in 74 patients. Forty patients had gold standard comparison. Twenty‐eight patients underwent resective surgery. SISCOM was concordant to site of surgery in 82%. An additional 12 patients underwent invasive EEG monitoring but were not suitable for surgery. SISCOM was concordant multifocal in 75%. Two years postsurgical follow‐up of 26 patients showed favorable outcome in 22 (Engel class I and class II). Significance: SISCOM is a highly valuable diagnostic tool to localize the seizure‐onset zone in nonlesional and extratemporal epilepsies. Outcome in this patient group was unexpectedly good, even in patients with nonlesional MRI. The high correlation with ECoG and site of successful surgery is a strong indicator that outcome prediction in this patient group should be adapted accordingly, which may encourage more patients to undergo electrode implantation and subsequent successful surgery. Statistical analysis showed that SISCOM with shorter duration of seizures, focal seizures, and lesional MRI was more likely to generate implantation hypothesis.     

Local spatial effect of 50 Hz cortical stimulation in humans

Purpose: Cortical stimulation to abort seizures is under human investigation. Ideal electrode placement and stimulating parameters are unknown with poor understanding of tissue volume affected by stimulation or duration and nature of its effect on cortical activity. To help characterize this effect, we analyzed electrocorticography (ECoG) recorded adjacent to stimulated contacts during and after bipolar stimulation in patients undergoing functional cortical mapping with subdural electrodes. Methods: We analyzed four functional mapping procedures in three patients. One row of contacts was chosen for bipolar stimulation at sequential distances. Stimulation parameters were those used for functional mapping. Pooled Teager energy (TE) and band power were calculated for: (1) baseline, (2) 5 s during stimulation, and (3) 5–15 s after the stimulus. Results: Average TE increased during stimulation, falling with distance from the stimulus. Average poststimulus TE increased (284–905%) compared to baseline. Increased TE was observed: (1) up to 10 s after stimulation, (2) stimulation amplitudes of 4 mA or greater, and (3) up to 2 cm from the stimulus. There was no difference in poststimulus TE between the stimulated pair of contacts and outside the pair. Greatest increase in poststimulus signal power occurred in beta and gamma bands. Conclusions: Human cortical stimulation of 50 Hz resulted in elevated ECoG energy measurements up to 10 s poststimulation. Contacts >2 cm from stimulated electrodes did not show significant response to stimulation. Separating contacts >2 cm on the cortical surface may not result in efficacious treatment of seizure activity using common stimulation amplitudes (2–10 mA).     

癫痫发作间期和亚临床发作期脑SPECT痫灶定位对比研究

目的：研究癫痫亚临床发作期和发作间期脑ＳＰＥＣＴ的痫灶定位诊断价值。方法：建立亚临床发作期脑血流灌注显像方法，与间期显像对比分析定位；并结合脑ＣＴ、ＥＥＧ、ＥＣｏＧ和疗效综合评价其痫灶定位诊断价值。结果：间期ＳＰＥＣＴ阳性率、准确率、灵敏度分别为：９０．９１％、７７．２７％、８９．４７％，亚临床发作期分别为：９５．４５％、９０．９１％、１００％，优于传统定位诊断。亚临床发作期病灶放射性摄取比值也有明显增加，ＥＣｏＧ、病检阳性率１００％，远期随访有效率９０．９１％。结论：ＳＰＣＥＴ具有较高的痫灶定位诊断价值，运用亚临床发作期显像可明显提高痫灶定位阳性率、准确性和灵敏度，表明亚临床发作期ＳＰＥＣＴ安全易行，能呈现ｒＣＢＦ增加，反映出发作期的显像特征     

Remission of Seizures and Predictors of Intractability in Long-Term Follow-Up

In an incidence cohort, remission and relapse rates and determinants were studied in 178 patients followed long-term. A comparative study of predictive factors was performed in 40 patients with histories of antiepileptic (AED)-drug-refractory epileptic seizures in the last 10 years of follow-up and compared with the other 138 cohort subjects. The two groups were cross-tabulated with 353 variables of family history, obstetric, developmental and seizure histories, and current medical and social status. Multivariate analyses were applied for control of confounding. Defined or probable remote symptomatic etiology of seizures, abnormal neurologic development/ status, high initial seizure frequency, occurrence of status epilepticus, and poor short-term effects of AED therapy were significantly associated with long-term AED refractoriness. On logistic regression analyses, poor short-term outcome of AED therapy [odds ratio (OR) 3.6; 95% confidence interval (CI) 1.2–10.4], occurrence of status epilepticus (OR 11.4; 95% CI 3.2–41.0), high initial seizure frequency (OR 4.6; 95% CI 1.1–19.3), and remote symptomatic seizure etiology (OR 2.9; 95% CI 1.1–8.2) remained the only independent predictors of seizure intractability. These factors enable early assessment of need for epilepsy surgery.     

The effects on cognitive performance of tailored resection in surgery for nonlesional mesiotemporal lobe epilepsy

PURPOSE: Mesiotemporal lobe epilepsy (MTLE) can be treated with different surgical approaches. In tailored resections, neocortex is removed beyond "standard" margins when spikes are present in the electrocorticogram. We hypothesized that these larger resections are justified because spiking neocortex is dysfunctional. This would imply that in patients with spikes (a) postoperative cognitive performance is not affected, and (b) preoperative performance is worse than without spikes. METHODS: We studied 80 operated-on MTLE patients with pathologically confirmed nonlesional hippocampal sclerosis. All patients were left-sided language dominant and underwent cognitive tests 6 months pre- and postoperatively. A repeated measures analysis of variance (ANOVA) was performed, looking for within- and between-subjects interactions with presence of intraoperative neocortical spikes. RESULTS: Intraoperatively, neocortical spikes were present in 61% of patients. Improved postoperative cognitive outcome was seen only in left-sided patients with spikes. Their performance IQ (PIQ) increased by 8.1 points (95% confidence interval, 3.8-12.3; p = 0.02), and visual naming latency by 12.8 s (95% CI, 2.1-23.5; p = 0.07). Conversely, in left-sided patients without spikes, naming latency declined by 7.5 s (95% CI, -2.3-17.2; p = 0.07). Preoperative scores were comparable except for a 15.3-point (95% CI, 0.1-30.5; p = 0.02) lower VIQ in left-sided patients without spikes. CONCLUSIONS: Tailoring does not harm cognitive performance and is, in left-sided MTLE, associated with postoperative improvement. Left-sided MTLE without neocortical spikes has lower verbal scores, which tend to decline after standard resection and may represent a special pathophysiologic entity.     

Isoflurane anesthesia induces biphasic effect on dopamine release in the rat striatum

The effect of isoflurane anesthesia on changes in the extracellular concentrations of dopamine (DA) and its metabolites (3-methoxytyramine (3-MT), 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA)) modulated by pargyline, monoamine oxidase inhibitor, was studied using in vivo microdialysis techniques. A microdialysis probe was implanted into the right striatum of male SD rats. Each rat (n=5-6) was given saline or the same volume of 30 or 75 mg kg(-1) pargyline intraperitoneally with or without 1 h isoflurane anesthesia (1 or 3%). Isoflurane anesthesia increased the extracellular concentration of DA in high dose (3%) and increased the metabolite concentrations in a dose-dependent manner. Pargyline administration increased the extracellular concentration of DA and 3-MT, and decreased that of other metabolites. After 30 mg kg(-1) pargyline treatment, 1% isoflurane-induced DA release and increasing of 3-MT were preserved, whereas high dose isoflurane (3%) decreased the concentration of metabolites (DOPAC and HVA), despite of the increase by low dose isoflurane (DOPAC). When 75 mg kg(-1) pargyline was administered, isoflurane anesthesia decreased the concentration of DA and DOPAC. The isoflurane-induced 3-MT increase was preserved in all experiments. Our results suggest that isoflurane anesthesia induced biphasic effect on DA regulation probably by the potentiation of DA release and the inhibition of DA synthesis. Isoflurane might modulate DA homeostasis presynaptically.     

术中B超在神经外科中的应用

目的探讨术中B超在神经外科手术中实时定位的应用价值。方法在术中B超的指引下对33例颅内病变进行手术切除。结果33例中明确定位28例(84.8%)。此28例中,肿瘤全切21例,次全切除7例;2例术后神经功能障碍加重,无严重手术并发症,无手术死亡。结论术中B超对皮层下的囊性和密度较高、边界清楚的实质性病灶显示清楚,定位准确,可帮助术中确定皮层切口和手术路径,减少神经功能障碍的发生。     

Progressive Unilateral Encephalopathy of Childhood (Rasmussen's Syndrome): A Reappraisal

Summary: Twelve children with Rasmussen's encephalitis underwent hemispherectomy and have been followed for an average of 9.15 years. Our decision-making process leads to early, rather than late operation. Because hemiplegia is inevitable with or without operation, earlier operation may allow such children to resume a more normal life. We postulate that earlier operation may prevent some of the intellectual decline that accompanies the continued seizures and their treatment. In view of the variable pathologic findings and lack of evidence of a viral etiology, we suggest either use of the term "progressive unilateral encephalopathy of childhood" or "Rasmussen's syndrome" in recognition of its heritage.     

Relief of Seizures from a Predominantly Posterior Temporal Tumor with Anterior Temporal Lobectomy

We report the relief of intractable complex partial seizures in a patient with a posteromesial temporal lobe hamartoma after anterior temporal lobectomy, despite minimal tumor removal. We suggest that the key to successful treatment is the mainly medial, or limbic, location of the tumor, which apparently requires anterior limbic structures for full clinical expression of seizures. We conclude that excision anterior to a posterior temporal lesion can result in seizure relief and that a medial tumor location may be important for successful treatment.     

脑电监测颅内蛛网膜囊肿继发癫(癎)的显微外科治疗

目的:探讨颅内蛛网膜囊肿(IAC)与癫癎的关系以及显微外科治疗方法。方法:应用脑电监测对颅内IAC伴癫癎的26例患者进行显微手术治疗。均行颅内IAC切除,致灶局限于脑非功能区者行致灶切除;致灶局限于脑功能区行灶区皮质热灼术。结果:26例患者中完全不发作者11例,显著改善者10例,无变化者5例。结论:颅内IAC可引起癫癎,显微手术切除IAC的同时,应用脑电监测行致灶切除和(或)皮质热灼术,对IAC伴癫癎患者的治疗较为理想。     

Significance of Spikes at Temporal Lobe Electrocorticography

Summary: Among 87 consecutive patients operated on under local anesthesia, few aspects of pre- and posttemporal lobe resection electrocorticograms (ECoG) yielded prognostic data. Preresection spikes were most common in the hippocampus, followed in order of frequency by the anterior temporal convexity and the inferior temporal surface. Moderately frequent (>10 spikes/100 s) preresection spikes appeared beyond the subsequent resection line in the posterior temporal region in 16 of 87 (18%) and in orbital frontal cortex in 12 of 87 (14%). Although many hippocampus spikes portended a favorable outcome and rare spikes an unfavorable one, preresection spike quantity otherwise failed to distinguish outcome groups. Absolute quantity of postresection spikes and change from preresection quantity in any region did not correlate with outcome except for the insula, where relatively abundant spikes portended favorable outcomes. Postresection electrographic seizures were rare but occurred equally in all outcome groups. No significant change in spike incidence occurred between the first and last 10-min epoch of the 30-min postresection recording.     

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.