The role of presurgical EEG parameters and of reoperation for seizure outcome in temporal lobe epilepsy

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-free outcome and safety of repeated epilepsy surgery for persistent or recurrent seizures

OBJECTIVE

Reoperation may be an option for select patients with unsatisfactory seizure control after their first epilepsy surgery. The aim of this study was to describe the seizure-free outcome and safety of repeated epilepsy surgery in our tertiary referral center.

METHODS

Thirty-eight patients with focal refractory epilepsy, who underwent repeated epilepsy surgeries and had a minimum follow-up time of 12 months after reoperation, were included. Systematic reevaluation, including comprehensive neuroimaging and noninvasive (n = 38) and invasive (n = 25, 66%) video-electroencephalography monitoring, was performed. Multimodal 3D resection maps were created for individual patients to allow personalized reoperation.

RESULTS

The median time between the first operation and reoperation was 74 months (range 5-324 months). The median age at reoperation was 34 years (range 1-74 years), and the median follow-up was 38 months (range 13-142 months). Repeat MRI after the first epilepsy surgery showed an epileptogenic lesion in 24 patients (63%). The reoperation was temporal in 18 patients (47%), extratemporal in 9 (24%), and multilobar in 11 (29%). The reoperation was left hemispheric in 24 patients (63%), close to eloquent cortex in 19 (50%), and distant from the initial resection in 8 (21%). Following reoperation, 27 patients (71%) became seizure free (Engel class I), while 11 (29%) continued to have seizures. There were trends toward better outcome in temporal lobe epilepsy and for unilobar resections adjacent to the initial surgery, but there was no difference between MRI lesional and nonlesional patients. In all subgroups, Engel class I outcome was at least 50%. Perioperative complications occurred in 4 patients (11%), with no fatalities.

CONCLUSIONS

Reoperation for refractory focal epilepsy is an effective and safe option in patients with persistent or recurrent seizures after initial epilepsy surgery. A thorough presurgical reevaluation is essential for favorable outcome.

Distribution of postictal slowing has an additional yield to interictal epileptiform discharge in predicting surgical outcomes in temporal lobe epilepsy

OBJECTIVE

To investigate whether the slowing of bilateral postictal scalp electroencephalography (EEG) after focal impaired awareness seizures is associated with poor seizure outcomes after temporal lobe epilepsy (TLE) surgery.

METHODS

This retrospective cohort study was conducted in the Department of Epileptology, Tohoku University Hospital from 2010 to 2020. The study included 42 patients with TLE who underwent a detailed presurgical evaluation and sequential resective surgery for the unilateral probable epileptogenic temporal lobe with 1 year or more of follow-up. We reviewed the interictal epileptiform distribution and those of the ictal and postictal epochs of the first focal impaired awareness seizure recorded in presurgical scalp EEG. We classified patients either with postoperative seizure-free status (Engel I) as group A or those with seizure persistence (Engel II-IV) as group B.

RESULTS

Of 42 patients, 29 (69%) were classified into group A. Compared with group B, group A had a lower number of bilateral postictal polymorphic delta activity (PPDA) (10.3%: 61.5%) and bilateral interictal epileptiform discharges (IEDs) (13.8%: 69.2%) (P = 0.003, P = 0.001, respectively). A combined analysis of bilateral PPDA and IEDs per individual patient showed significantly more frequent seizure persistence after surgery (P < 0.0001) than a single analysis of bilateral IEDs or PPDA alone (P = 0.001). The regression analysis revealed that bilaterally distributed PPDA or IEDs had 13.50 or 13.72 times higher odds of persisting seizures within 1 year of surgery (95% confidence interval: 1.90-95.88; 2.12-88.87, respectively) (P = 0.009, 0.006).

SIGNIFICANCE

The results of this study revealed that the bilateral distribution of PPDA was associated with poor postoperative seizure outcomes in patients with TLE, as well as bilateral IEDs. Additionally, the concomitant bilateral distribution of interictal and postictal changes is a strong indicator of poor surgical outcomes.

Multiple mechanisms shape the relationship between pathway and duration of focal seizures

A seizure's electrographic dynamics are characterized by its spatiotemporal evolution, also termed dynamical 'pathway', and the time it takes to complete that pathway, which results in the seizure's duration. Both seizure pathways and durations have been shown to vary within the same patient. However, it is unclear whether seizures following the same pathway will have the same duration or if these features can vary independently. We compared within-subject variability in these seizure features using (i) epilepsy monitoring unit intracranial EEG (iEEG) recordings of 31 patients (mean: 6.7 days, 16.5 seizures/subject), (ii) NeuroVista chronic iEEG recordings of 10 patients (mean: 521.2 days, 252.6 seizures/subject) and (iii) chronic iEEG recordings of three dogs with focal-onset seizures (mean: 324.4 days, 62.3 seizures/subject). While the strength of the relationship between seizure pathways and durations was highly subject-specific, in most subjects, changes in seizure pathways were only weakly to moderately associated with differences in seizure durations. The relationship between seizure pathways and durations was strengthened by seizures that were 'truncated' versions, both in pathway and duration, of other seizures. However, the relationship was weakened by seizures that had a common pathway, but different durations ('elasticity'), or had similar durations, but followed different pathways ('semblance'). Even in subjects with distinct populations of short and long seizures, seizure durations were not a reliable indicator of different seizure pathways. These findings suggest that seizure pathways and durations are modulated by multiple different mechanisms. Uncovering such mechanisms may reveal novel therapeutic targets for reducing seizure duration and severity.

Improving the prediction of epilepsy surgery outcomes using basic scalp EEG findings

OBJECTIVE

This study aims to evaluate the role of scalp electroencephalography (EEG; ictal and interictal patterns) in predicting resective epilepsy surgery outcomes. We use the data to further develop a nomogram to predict seizure freedom.

METHODS

We retrospectively reviewed the scalp EEG findings and clinical data of patients who underwent surgical resection at three epilepsy centers. Using both EEG and clinical variables categorized into 13 isolated candidate predictors and 6 interaction terms, we built a multivariable Cox proportional hazards model to predict seizure freedom 2 years after surgery. Harrell's step-down procedure was used to sequentially eliminate the least-informative variables from the model until the change in the concordance index (c-index) with variable removal was less than 0.01. We created a separate model using only clinical variables. Discrimination of the two models was compared to evaluate the role of scalp EEG in seizure-freedom prediction.

RESULTS

Four hundred seventy patient records were analyzed. Following internal validation, the full Clinical + EEG model achieved an optimism-corrected c-index of 0.65, whereas the c-index of the model without EEG data was 0.59. The presence of focal to bilateral tonic-clonic seizures (FBTCS), high preoperative seizure frequency, absence of hippocampal sclerosis, and presence of nonlocalizable seizures predicted worse outcome. The presence of FBTCS had the largest impact for predicting outcome. The analysis of the models' interactions showed that in patients with unilateral interictal epileptiform discharges (IEDs), temporal lobe surgery cases had a better outcome. In cases with bilateral IEDs, abnormal magnetic resonance imaging (MRI) predicted worse outcomes, and in cases without IEDs, patients with extratemporal epilepsy and abnormal MRI had better outcomes.

SIGNIFICANCE

This study highlights the value of scalp EEG, particularly the significance of IEDs, in predicting surgical outcome. The nomogram delivers an individualized prediction of postoperative outcome, and provides a unique assessment of the relationship between the outcome and preoperative findings.

Epilepsy surgery: Late seizure recurrence after initial complete seizure freedom

OBJECTIVE

This study was undertaken to improve understanding of late relapse following epilepsy surgery in pharmacoresistant epilepsy.

METHODS

Retrospective comparison was made of 99 of 1278 patients undergoing surgery during 1999-2015 with seizure relapses after at least 2 years of complete seizure freedom with matched controls experiencing continued long-term seizure freedom. Univariate and multivariate analyses were performed.

RESULTS

With a mean follow-up of 9.7 years, mean time to seizure relapse was 56.6 months. In multivariate analysis, incomplete resection based on magnetic resonance imaging (MRI), bilateral lesions on preoperative MRI, and epilepsy onset in the first year of life carried a significantly higher risk of late relapse. In patients with late relapse, additional functional imaging with positron emission tomography had been performed significantly more often. Although the differences were not significant in multivariate analysis, doses of antiepileptic drugs were higher in the relapse group preoperatively and in the first 24 months and complete withdrawal was more frequent in the control group (68% vs. 51%). Regarding seizure frequency, most patients had mild seizure relapse (single relapse seizure or <1/month).

SIGNIFICANCE

In our predominantly lesional cohort, complete resection of the MRI lesion is the most important factor to maintain long-term seizure freedom. Two patterns of recurrence were identified: (1) incomplete resected lesions with seizure generation in proximity to the initial resection and (2) epileptogenic networks not detected preoperatively or evolving in the postoperative interval and manifesting with new clinical and diagnostic features.

Anticonvulsant Effects of Dingxian Pill in Pentylenetetrazol-Kindled Rats

Dingxian pill has been used as an antiepilepsy agent in China from ancient to modern times, of which the concrete pharmacological characterization and the underlying molecular mechanism remain unclear. The present study was undertaken to investigate them by animal behavior, electroencephalogram (EEG), Morris water maze, immunohistochemistry, transcriptomics, and real-time PCR. In our results, the treatment of Dingxian pill dose-dependently inhibited PTZ-induced seizure-like behavior and reduced the seizure grades, LFP power spectral density, and brain wave of the epileptiform EEG component induced by PTZ. In Morris water maze tests, the learning and memory ability of kindled epileptic rats could be attenuated more efficiently by Dingxian pill. For the immediate early gene c-fos, the expression was reduced after Dingxian pill treatment, and the difference was significant between the treatment and the model group. Through the transcriptome analysis of the gene expression in hippocampus, Egr3, Nrg, Arc, and Ptgs2, closely related to epilepsy, had been proved to be downregulated by application of Dingxian pill. All of the results not only highlight the antiepileptic effects of Dingxian pill and its molecular mechanism, but also provide a modern validity theory for the clinical application of traditional Chinese medicine (TCM).

Improvement of intellectual outcomes in 20 children with refractory epilepsy after individualized surgery

Background:

Refractory epilepsy is a common and troublesome neurosurgical disease. This study is designed to compare seizure control and degrees in intellectual outcome in children with refractory epilepsy after surgical treatment.

Methods:

20 children with refractory epilepsy were treated with tailored epilepsy surgery or vagus nerve stimulation (VNS). We used the Engel Epilepsy Surgery Outcome Scale to evaluate seizure control and the Wechsler Intelligence Scale for Children, fourth edition (WISC-IV), to test the children's intellectual outcomes 7-day preoperative and 3-, 6-, and 12-month postoperative.

Results:

In total, 14 cases were seizure free (Engel I) and 2 cases to have suffered few attacks since surgery (Engel II). In two cases, the frequency of seizures decreased by >90% (Engel III). In the remaining two cases, the effects of surgery on seizure control were not obvious (Engel IV). All children completed the WISC-IV test. On average, postoperative intelligence quotient (IQ) increased by 6.35 points 12-month postsurgery compared with the results of the preoperative tests (P < 0.01). Second, intellectual outcomes after surgery in the Engel I and II groups increased by >3.88 points compared with in the Engel III and IV groups (P < 0.05). Finally, there were no fatal complications over the long-term follow-up except for intracranial infection of two cases; postoperative subcutaneous hematoma occurred in one case and hoarseness in one case.

Conclusion:

Individualized epilepsy surgery is safe and effective for children with refractory epilepsy. It can control or reduce the frequency of postoperative attacks as well as improve postoperative intellectual outcomes to different degrees.

Does early postoperative drug regimen impact seizure control in patients undergoing temporal lobe resections?

OBJECTIVE

To evaluate the impact of postoperative antiepileptic drug (AED) load on seizure control in patients who underwent surgical treatment for pharmacoresistant mesiotemporal lobe epilepsy during the first two postoperative years.

PATIENTS AND METHODS

532 consecutive patients (48.7% males and 51.7% females) who underwent surgical treatment for mesiotemporal lobe epilepsy were retrospectively evaluated regarding effects of AED load on seizures control during the first 2 years following epilepsy surgery. We analyzed whether postoperative increases in postoperative AED load are associated with better seizure control in patients initially not seizure free, and if postoperative decreases in postoperative AED load would increase the risk for seizure persistence or recurrence. For statistical analyses, Fisher's exact and Wilcoxon test were applied.

RESULTS

68.9, 64.0 and 59.1% of patients were completely seizure free (Engel Ia) at 3, 12 and 24 months after surgery, respectively. Patients in whom daily drug doses were increased did not have a higher rate of seizure freedom at any of the three follow-up periods. Of 16 patients achieving secondary seizure control at 12 months after surgery, only one did so with an increase in drug load in contrast to 15 patients who experienced a running down of seizures independent of drug load increases. Decreases in drug load did not significantly increase the risk for seizure recurrence. Of postoperatively seizure free patients at 3 months after surgery in whom AED were consequently reduced, 85% remained completely seizure free at 1 year and 76% at 1 year after surgery, respectively, as opposed to 86% each when AED was not reduced (differences n.s.). Mean daily drug load was significantly lower in seizure free patients at 12 and 24 months compared to patients with ongoing seizures.

CONCLUSION

In this large patient cohort stratified to the epilepsy syndrome neither did a postoperative reduction in drug load significantly increase the risk for seizure relapse nor did increases in drug dosages lead to improved seizure control. Mean drug load was on average lower in seizure free- than non-seizure free patients at 12 and 24 months of follow-up. Secondary seizure control after initial postoperative seizures in > 90% of cases occurred as a running down, independent of an AED increase. Thus, the effect of the surgical intervention rather than the postoperative drug regimen was the key determinant for seizure control. This finding supports a curative role of temporal lobe surgery rather than an effect rendering the majority of patients' pharmacoresponsive with a critical role of the antiepileptic drug regime for seizure control.