The value of ictal scalp EEG in focal epilepsies surgery: a retrospective analysis

OBJECTIVE

To describe the association between preoperative ictal scalp electroencephalogram (EEG) results and surgical outcomes in patients with focal epilepsies.

METHODS

The data of consecutive patients with focal epilepsies who received surgical treatments at our center from January 2012 to December 2021 were retrospectively analyzed.

RESULTS

Our data showed that 44.2% (322/729) of patients had ictal EEG recorded on video EEG monitoring during preoperative evaluation, of which 60.6% (195/322) had a concordant ictal EEG results. No significant difference of surgery outcomes between patients with and without ictal EEG was discovered. Among MRI-negative patients, those with concordant ictal EEG had a significantly better outcome than those without ictal EEG (75.7% vs. 43.8%, p = 0.024). Further logistic regression analysis showed that concordant ictal EEG was an independent predictor for a favorable outcome (OR = 4.430, 95%CI 1.175-16.694, p = 0.028). Among MRI-positive patients, those with extra-temporal lesions and discordant ictal EEG results had a worse outcome compared to those without an ictal EEG result (44.7% vs. 68.8%, p = 0.005). Further logistic regression analysis showed that discordant ictal EEG was an independent predictor of worse outcome (OR = 0.387, 95%CI 0.186-0.807, p = 0.011) in these patients. Furthermore, our data indicated that the number of seizures was not associated with the concordance rates of the ictal EEG, nor the surgical outcomes.

CONCLUSIONS

The value of ictal scalp EEG for epilepsy surgery varies widely among patients. A concordant ictal EEG predicts a good surgical outcome in MRI-negative patients, whereas a discordant ictal EEG predicts a poor postoperative outcome in lesional extratemporal lobe epilepsy.

Seizure outcome determinants in children after surgery for single unilateral lesions on magnetic resonance imaging: Role of preoperative ictal and interictal electroencephalography

OBJECTIVE

To determine whether an ictal electroencephalographic (EEG) recording as part of presurgical evaluation of children with a demarcated single unilateral magnetic resonance imaging (MRI) lesion is indispensable for surgical decision-making, we investigated the relationship of interictal/ictal EEG and seizure semiology with seizure-free outcome.

METHODS

Data were obtained retrospectively from consecutive patients (≤18 years old) undergoing epilepsy surgery with a single unilateral MRI lesion at our institution over a 6-year period. Video-telemetry EEG (VT-EEG) was classified as concordant or nonconcordant/noninformative in relation to the MRI lesion location. The odds of seizure-free outcome associated with nonconcordant versus concordant for semiology, interictal EEG, and ictal EEG were compared separately. Multivariate logistic regression was conducted to correct for confounding variables.

RESULTS

After a median follow-up of 26 months (interquartile range = 17-37.5), 73 (69%) of 117 children enrolled were seizure-free. Histopathological diagnoses included low-grade epilepsy-associated tumors, n = 46 (39%); focal cortical dysplasia (FCD), n = 33 (28%); mesial temporal sclerosis (MTS), n = 23 (20%); polymicrogyria, n = 3 (3%); and nondiagnostic findings/gliosis, n = 12 (10%). The odds of seizure freedom were lower with a nonconcordant interictal EEG (odds ratio [OR] = .227, 95% confidence interval [CI] = .079-.646, p = .006) and nonconcordant ictal EEG (OR = .359, 95% CI = .15-.878, p = .035). In the multivariate logistic regression model, factors predicting lower odds for seizure-free outcome were developmental delay/intellectual disability and higher number of antiseizure medications tried, with a nonsignificant trend for "nonconcordant interictal EEG." In the combined subgroup of patients with FCD and tumors (n = 79), there was no significant relationship of VT-EEG factors and seizure outcomes, whereas in children with MTS and acquired lesions (n = 25), a nonconcordant EEG was associated with poorer seizure outcomes (p = .003).

SIGNIFICANCE

An ictal EEG may not be mandatory for presurgical evaluation, particularly when a well-defined single unilateral MRI lesion has been identified and the interictal EEG is concordant.

The surgical treatment of epilepsy

In 2009, the Commission for Epilepsy Surgery of the Italian League Against Epilepsy (LICE) conducted an overview about the techniques used for the pre-surgical evaluation and the surgical treatment of epilepsies. The recognition that, in selected cases, surgery can be considered the first-line approach, suggested that the experience gained by the main Italian referral centers should be pooled in order to provide a handy source of reference. In light of the progress made over these past years, some parts of that first report have accordingly been updated. The present revision aims to harmonize the general principles regulating the patient selection and the pre-surgical work-up, as well as to expand the use of epilepsy surgery, that still represents an underutilized resource, regrettably. The objective of this contribution is drawing up a methodological framework within which to integrate the experiences of each group in this complex and dynamic sector of the neurosciences.

Surgery in intractable epilepsy-physicians' recommendations and patients' decisions

OBJECTIVES

To identify demographic and clinical variables independently associated with patients' decisions against their physicians' recommendations for resective epilepsy surgery or further scalp video-EEG monitoring (sca-VEM), semi-invasive (sem-)VEM with foramen ovale and/or peg electrodes, and invasive (in-)VEM.

METHODS

Consecutive patients, who underwent presurgical assessment with at least one sca-VEM between 2010 and 2014, were included into this retrospective analysis. Multivariate analysis was used to identify independent variables associated with patients' decisions.

RESULTS

Within the study period, 352 patients underwent 544 VEM sessions comprising 451 sca-, 36 sem-, and 57 in-VEMs. Eventually, 96 patients were recommended resective surgery, and 106 were ineligible candidates; 149 patients denied further necessary VEMs; thus, no decision could be made. After sca- or additional sem-VEM, nine out of 51 eligible patients (17.6%) rejected resection. One hundred and ten patients were recommended in-VEM, 52 of those (47.2%) declined. Variables independently associated with rejection of in-VEM comprised intellectual disability (OR 4.721, 95% CI 1.047-21.284), extratemporal focal aware non-motor seizures ("aura") vs. no "aura" (OR 0.338, 95% CI 0.124-0.923), and unilateral or bilateral vs. no MRI lesion (OR 0.248, 95% CI 0.100-0.614 and 0.149, 95% CI 0.027-0.829, respectively).

CONCLUSIONS

During and after presurgical evaluation, patients with intractable focal epilepsy declined resections and intracranial EEGs, as recommended by their epileptologists, in almost 20% and 50% of cases. This calls for early and thorough counseling of patients on risks and benefits of epilepsy surgery. Future prospective studies should ask patients in depth for specific reasons why they decline their physicians' recommendations.

Analysis of Interictal Epileptiform Discharges in Mesial Temporal Lobe Epilepsy Using Quantitative EEG and Neuroimaging

Objective: Investigate areas of correlation between gray matter volumes by MRI and interictal EEG source maps in subtypes of mesial temporal lobe epilepsy (MTLE). Method: 71 patients and 36 controls underwent 3T MRI and and routine EEG was performed. Voxel-based morphometry (VBM) was used for gray matter analysis and analysis of interictal discharge sources for quantitative EEG. Voxel-wise correlation analysis was conducted between the gray matter and EEG source maps in MTLE subtypes. Results: The claustrum was the main structure involved in the individual source analysis. Twelve patients had bilateral HA, VBM showed bilateral hippocampal. Twenty-one patients had right HA, VBM showed right hippocampal and thalamic atrophy and negatively correlated involving the right inferior frontal gyrus and insula. Twenty-two patients had left HA, VBM showed left hippocampal atrophy and negatively correlated involving the left temporal lobe and insula. Sixteen patients had MTLE without HA, VBM showed middle cingulate gyrus atrophy and were negatively correlated involving extra-temporal regions, the main one located in postcentral gyrus. Conclusions: Negative correlations between gray matter volumes and EEG source imaging. Neuroanatomical generators of interictal discharges are heterogeneous and vary according to MTLE subtype. Significance: These findings suggest different pathophysiological mechanisms among patients with different subtypes of MTLE.

Presurgical evaluation of temporal lobe epilepsy: Is an outpatient prolonged ambulatory EEG study sufficient to recommend a surgical resection?

Purpose

Inpatient Video EEG Monitoring (VEM) is the typical study performed in presurgical evaluations. It is expensive and not widely available in developing countries. Recent studies suggested that in selected patients with mesial temporal lobe epilepsy secondary to unilateral mesial temporal sclerosis (MTS), the recording of unilateral interictal epileptiform activity ipsilateral to the MTS may yield sufficient presurgical EEG data. Outpatient prolonged ambulatory EEG (AEEG) could be an alternative in these cases. The purpose of this study was to compare the post-surgical seizure outcome and costs between patients evaluated with AEEG versus VEM.

Methods

Thirty patients with TLE were included: 21 evaluated with VEM and 9 with AmbEEG and underwent surgery between 2011 and 2017. The minimum, post-surgical follow-up period was 1 year.

Results

Seven of nine patients who underwent AEEG had seizures ipsilateral to MTS. In two patients only unilateral interictal activity ipsilateral to the lesion was recorded. All patients were free of disabling seizures (Engel Class I) at last follow-up. The mean cost per patient of AEEG was $980 and was $4680 for VEM.

Conclusion

AEEG may be used to identify candidates for temporal lobectomy in selected patients with unilateral lesional mesial TLE. This approach to EEG monitoring could make epilpesy surgery more affordable to some patients in developing countries.

Initiating a new national epilepsy surgery program: Experiences gathered in Georgia

Surgery is the most effective therapeutic approach for medically refractory epilepsies and a safe and cost-efficient treatment in terms of long-term expenses of direct, indirect, and intangible costs. Georgia is a Caucasian low- to middle-income country with a remarkable effort to deal with epileptic diseases, but without an appropriate epilepsy surgery program. To address the needs for such a service in this country, two joint German-Georgian projects were initiated in 2017 and 2019. In the framework of these projects, a productive exchange program involving German and Georgian experts was undertaken in the past two years. This program included training and mentoring for Georgian clinical colleagues, as well as joint case conferences and workshops with the aim of optimizing presurgical diagnostics and preparing for an epilepsy surgery program in Georgia. Finally, a postsurgical medium- and long-term follow-up scheme was organized as the third component of this comprehensive approach. As a result of our efforts, the first patients underwent anterior temporal lobectomy and all of them remain seizure-free up to the present day. Hence, epilepsy surgery is not only feasible, but also already available in Georgia. In this report, we aim to share our experiences in the initiation and implementation of surgical epilepsy intervention in Georgia and illustrate our recent endeavor and achievements.

Temporopolar amygdalohippocampectomy: seizure control and postoperative outcomes

OBJECTIVE

The objective of this study was to evaluate the efficacy and safety of a modified surgical approach for the treatment of temporal lobe epilepsy secondary to hippocampal sclerosis (HS). This modified approach, called temporopolar amygdalohippocampectomy (TP-AH), includes a transsylvian resection of the temporal pole and subsequent amygdalohippocampectomy utilizing the limen insula as an anatomical landmark.

METHODS

A total of 61 patients who were diagnosed with HS and underwent TP-AH between 2013 and 2017 were enrolled. Patients performed pre- and postoperative diffusion tensor imaging and were classified according to Engel's scale for seizure control. To evaluate the functional preservation of the temporal stem white-matter fiber tracts, the authors analyzed postoperative Humphrey perimetries and pre- and postoperative neurocognitive performance (Rey Auditory Verbal Learning Test [RAVLT], Weschler Memory Scale-Revised [WMS-R], intelligence quotient [IQ], Boston Naming Test [BNT], and semantic and phonemic fluency). Demographic data and surgical complications were also recorded and described.

RESULTS

After a median follow-up of 36 ± 16 months, 46 patients (75.4%) achieved Engel class I, of whom 37 (60.6%) were Engel class IA. No significant changes in either the inferior frontooccipital fasciculus and optic radiation tractography were observed postoperatively for both left- and right-side surgeries. Reliable perimetry was obtained in 40 patients (65.6%), of whom 27 (67.5%) did not present any visual field defects (VFDs) attributable to surgery, while 12 patients (30%) presented with quadrant VFD, and 1 patient (2.5%) presented with hemifield VFD. Despite a significant decline in verbal memory (p = 0.007 for WMS-R, p = 0.02 for RAVLT recognition), there were significant improvements in both IQ (p < 0.001) and visual memory (p = 0.007). Semantic and phonemic fluency, and scores on the BNT, did not change postoperatively.

CONCLUSIONS

TP-AH provided seizure control similar to historical temporal lobe approaches, with a tendency to preserve the temporal stem and a satisfactory incidence of VFD. Despite a significant decline in verbal memory, there were significant improvements in both IQ and visual memory, along with preservation of executive function. This approach can be considered a natural evolution of the selective transsylvian approach.

Changing concepts in presurgical assessment for epilepsy surgery

Candidates for epilepsy surgery must undergo presurgical evaluation to establish whether and how surgical treatment can stop seizures without causing neurological deficits. Various techniques, including MRI, PET, single-photon emission CT, video-EEG, magnetoencephalography and invasive EEG, aim to identify the diseased brain tissue and the involved network. Recent technical and methodological developments, encompassing both advances in existing techniques and new combinations of technologies, are enhancing the ability to define the optimal resection strategy. Multimodal interpretation and predictive computer models are expected to aid surgical planning and patient counselling, and multimodal intraoperative guidance is likely to increase surgical precision. In this Review, we discuss how the knowledge derived from these new approaches is challenging our way of thinking about surgery to stop focal seizures. In particular, we highlight the importance of looking beyond the EEG seizure onset zone and considering focal epilepsy as a brain network disease in which long-range connections need to be taken into account. We also explore how new diagnostic techniques are revealing essential information in the brain that was previously hidden from view.

The Role of Interictal Epileptiform Discharges in Epilepsy Surgery Outcome

Background:

Epilepsy surgery is a fundamental treatment in refractory epilepsy. Video electroencephalographic (v-EEG) monitoring plays an essential role in presurgical evaluation of patients. However there are reports of favorable outcome based on interictal and magnetic resonance imaging (MRI) findings without any need for v-EEG monitoring in patients with temporal lobe epilepsy (TLE). This study aimed to investigate the prognostic effect of concordance between interictal findings and ictal and MRI data on postsurgical outcome of TLE and extratemporal lobe epilepsy (ETLE).

Methods:

A retrospective study was conducted on 199 patients with refractory focal epilepsy who were admitted for presurgical evaluation. The concordance between irritative zone (IZ) and seizure onset zone (SOZ) and also IZ and MRI lesion was registered, and subsequently the prognostic effect of relevancy on 1-year follow-up result based on Engel criteria was investigated.

Results:

In TLE and ETLE regarding relevancy between IZ and SOZ, 77.8% and 73.2% were concordant, 2.5% and 0% were discordant, and 19.6% and 26.8% had overlap, respectively. Concordance between IZ and MRI lesion was found in 76.6% and 51.2% of patients with TLE and ETLE while discordance was recorded in 2.5% and 12.2% and overlap registered in 20.9% and 36.6%, respectively. The concordance of interictal findings had no effect on postsurgical outcome of patients with TLE and ETLE.

Conclusions:

Our study showed that concordance of IZ with SOZ and MRI has no independent effect on postsurgical outcome of patients with TLE and ETLE. We suggest that excluding exceptional cases, v-EEG monitoring should be considered as the mainstay of presurgical evaluation.

A historical cohort of temporal lobe surgery for medically refractory epilepsy: a systematic review and meta-analysis to guide future nonrandomized controlled trial studies

OBJECTIVE

Recent trials for temporal lobe epilepsy (TLE) highlight the challenges of investigating surgical outcomes using randomized controlled trials (RCTs). Although several reviews have examined seizure-freedom outcomes from existing data, there is a need for an overall seizure-freedom rate estimated from level I data as investigators consider other methods besides RCTs to study outcomes related to new surgical interventions.

METHODS

The authors performed a systematic review and meta-analysis of the 3 RCTs of TLE in adults and report an overall surgical seizure-freedom rate (Engel class I) composed of level I data. An overall seizure-freedom rate was also collected from level II data (prospective cohort studies) for validation. Eligible studies were identified by filtering a published Cochrane meta-analysis of epilepsy surgery for RCTs and prospective studies, and supplemented by searching indexed terms in MEDLINE (January 1, 2012-April 1, 2018). Retrospective studies were excluded to minimize heterogeneity in patient selection and reporting bias. Data extraction was independently reverified and pooled using a fixed-effects model. The primary outcome was overall seizure freedom following surgery. The historical benchmark was applied in a noninferiority study design to compare its power to a single-study cohort.

RESULTS

The overall rate of seizure freedom from level I data was 72.4% (55/76 patients, 3 RCTs), which was nearly identical to the overall seizure-freedom rate of 71.7% (1325/1849 patients, 18 studies) from prospective cohorts (z = 0.134, p = 0.89; z-test). Seizure-freedom rates from level I and II studies were consistent over the years of publication (R2 < 0.01, p = 0.73). Surgery resulted in markedly improved seizure-free outcomes compared to medical management (RR 10.82, 95% CI 3.93-29.84, p < 0.01; 2 RCTs). Noninferiority study designs in which the historical benchmark was used had significantly higher power at all difference margins compared to using a single cohort alone (p < 0.001, Bonferroni's multiple comparison test).

CONCLUSIONS

The overall rate of seizure freedom for temporal lobe surgery is approximately 70% for medically refractory epilepsy. The small sample size of the RCT cohort underscores the need to move beyond standard RCTs for epilepsy surgery. This historical seizure-freedom rate may serve as a useful benchmark to guide future study designs for new surgical treatments for refractory TLE.

Is there a place for surgical treatment of nonpharmacoresistant epilepsy?

Epilepsy surgery has been shown to be the best possible treatment in well-defined and difficult-to-treat epilepsy syndromes, such as mesial temporal lobe epilepsy with unilateral hippocampal sclerosis, even early in the course of the disease if pharmacoresistance is proven. This review addresses the question if epilepsy surgery may be justified today even in nonpharmacoresistant cases. There are two possible groups of patients: first, there are epilepsy syndromes with a benign spontaneous course or with a potentially good treatment prognosis under appropriate antiepileptic drug (AED) treatment. Second, there are epilepsies with potentially worse AED treatment prognosis in which appropriate AED treatment has not yet been applied because of the short course of the disease, tolerability problems that prevented usually effective dosing, or adherence issues. In group one, the good spontaneous prognosis or the usually satisfying course under AED treatment in line with the commonly generalized underlying epileptogenesis does not suggest that epilepsy surgery is a realistic alternative, not even in cases with distinct focal clinical and/or electroencephalography (EEG) patterns like in Rolandic epilepsy with centrotemporal spikes. In the second group, the recent International League Against Epilepsy (ILAE) definition should allow assessment of individual pharmacoresistance early after the onset of the disease in order to avoid any delay. Concerns about a potential disease-specific or drug-specific cognitive decline that could be avoided in early surgery are speculative, a matter of controversial discussion, and certainly not relevant, if pharmacoresistance is consequently addressed in time according to the ILAE recommendations. One should also not forget that even in typically pharmacoresistant epilepsy syndromes that are suitable for surgical procedures, satisfying courses do exist that would not require early or any epilepsy surgery. Therefore, in almost any instance, epilepsy surgery as initial treatment or immediately after a first AED is still not recommended although, especially in cases with nonadherence to AEDs, it may be occasionally considered in order to outweigh the risks of ongoing seizures and epilepsy if surgery is not performed.

Post-operative nonketotic hyperglycemic induced focal motor status epilepticus related to treatment with corticosteroids following standard anterior temporal lobectomy

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Complications from standard ATL are uncommon and the use of post-operative corticosteroids may reduce complications.

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Following standard ATL, FMSE was present after treatment with corticosteroids that resolved after blood sugar control.

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After epilepsy surgery, corticosteroids should be used cautiously in people with comorbid diabetes mellitus.

Unusual ictal propagation patterns suggesting poor prognosis after temporal lobe epilepsy surgery: Switch of lateralization and bilateral asynchrony

OBJECTIVE

The objective of this study was to investigate unusual ictal propagation patterns in patients with drug-resistant temporal lobe epilepsy (TLE) and reveal their electrophysiological, neuroimaging, and prognostic properties after surgery.

METHODS

Among 248 patients with TLE who underwent scalp video-electroencephalographic (EEG) monitoring, 24 patients with 'switch of lateralization' or 'bilateral asynchrony' in at least one of their seizures (9.3%) were analyzed retrospectively. The postoperative outcome was determined in 16 patients who had undergone epilepsy surgery.

RESULTS

All but 5 of the included patients had hippocampal sclerosis (HS) as their magnetic resonance imaging (MRI) findings. Twelve out of 16 patients (75%) who had surgery were seizure-free for at least 1 year. Nine out of 12 patients (75%) with good outcome had unilateral interictal EEG discharges in temporal regions whereas 3 out of 4 patients with poor outcome had bilateral temporal interictal spiking (p = 0.018).

CONCLUSION

Unusual ictal propagation patterns are not always related to poor prognosis after surgery in patients with TLE. Patients with unilateral interictal spiking in the temporal region tend to have good outcome despite these unusual patterns. These patterns can also be seen in patients with TLE with other etiologies besides the well-known HS in MRI.

Unilateral temporal interictal epileptiform discharges correctly predict the epileptogenic zone in lesional temporal lobe epilepsy

OBJECTIVE

To evaluate the necessity of recording ictal electroencephalography (EEG) in patients with temporal lobe epilepsy (TLE) considered for resective surgery who have unilateral temporal interictal epileptiform discharges (IEDs) and concordant ipsitemporal magnetic resonance imaging (MRI) pathology. To calculate the necessary number of recorded EEG seizure patterns (ESPs) to achieve adequate lateralization probability.

METHODS

In a retrospective analysis, the localization and lateralization of interictal and ictal EEG of 304 patients with lesional TLE were analyzed. The probability of further contralateral ESPs was calculated based on a total of 1967 recorded ESPs, using Bayes' theorem.

RESULTS

Two hundred seventy-one patients had unilateral TLE, and in 98% of them (265 of 271), IEDs were recorded during video-EEG monitoring. Purely unilateral temporal IEDs were present in 61% (166 of 271 patients). Ipsilateral temporal MRI pathology was found in 83% (138 of 166). Ictal EEG was concordant with the clinical side of TLE in 99% (136 of 138) of these patients. Two patients had discordant ictal EEG with both ipsilateral and contralateral ESPs. Epilepsy surgery with resection in the lesioned temporal lobe was still performed, and both patients remain seizure-free. Probability calculations demonstrate that at least 6 recorded unilateral ESPs result in a >95% probability for a concordance of >0.9 of any further ESPs.

SIGNIFICANCE

The combination of purely unilateral temporal IED with ipsitemporal MRI pathology is sufficient to identify the epileptogenic zone, and the recording of ictal ESP did not add any surgically relevant information in these 138 patients. Rarely, discordant ESPs might be recorded, but the surgical outcome remains excellent after surgery on the lesioned side.