Long-term outcomes in patients after epilepsy surgery failure

Chronic intracranial EEG recordings and interictal spike rate reveal multiscale temporal modulations in seizure states

Many biological processes are modulated by rhythms on circadian and multidien timescales. In focal epilepsy, various seizure features, such as spread and duration, can change from one seizure to the next within the same patient. However, the specific timescales of this variability, as well as the specific seizure characteristics that change over time, are unclear. Here, in a cross-sectional observational study, we analysed within-patient seizure variability in 10 patients with chronic intracranial EEG recordings (185-767 days of recording time, 57-452 analysed seizures/patient). We characterized the seizure evolutions as sequences of a finite number of patient-specific functional seizure network states. We then compared seizure network state occurrence and duration to (1) time since implantation and (2) patient-specific circadian and multidien cycles in interictal spike rate. In most patients, the occurrence or duration of at least one seizure network state was associated with the time since implantation. Some patients had one or more seizure network states that were associated with phases of circadian and/or multidien spike rate cycles. A given seizure network state's occurrence and duration were usually not associated with the same timescale. Our results suggest that different time-varying factors modulate within-patient seizure evolutions over multiple timescales, with separate processes modulating a seizure network state's occurrence and duration. These findings imply that the development of time-adaptive treatments in epilepsy must account for several separate properties of epileptic seizures and similar principles likely apply to other neurological conditions.

Clinical factors associated with late seizure remission after failed epilepsy surgery

BACKGROUND

Some patients who initially fail epilepsy surgery later become seizure-free, but it is not clear how the clinical characteristics of the patients or post-operative modifications of anti-seizure medication (ASM) regimens contribute to late seizure remission.

METHODS

We performed a retrospective chart review of patients undergoing epilepsy surgery at the University of Washington Regional Epilepsy Center between 2007 and 2017, including patients receiving neocortical resection, temporal lobectomy, and hippocampal laser interstitial therapy (LITT) ablation. We assessed seizure freedom, ASM changes, seizure frequency at the first and last follow-up, and type of lesion. Two-tailed Fisher's exact test and Mann-Whitney U test were used for statistical analyses.

RESULTS

Two hundred and fifteen patients undergoing epilepsy surgery between 2007 and 2017 had both first and last follow-ups. Ninety-eight (46%) were not seizure-free at the first follow-up (mean 1.1 years post-operative). By the last follow-up (mean 4.7 years post-operative), 20% of those not initially seizure-free had become so. Those who were seizure-free at the last visit had lower median seizures per month in the first post-operative year (0.21 versus 0.95 per month in those not seizure-free, p < 0.001). There was also a significantly higher proportion of patients with cavernomas who were seizure-free at the last visit (25% vs. 1% of those not seizure-free at the last visit; p = 0.001), but no other differences in clinical characteristics. Of the 98 patients who had seizures at the first follow-up, 63% underwent post-operative modification of their ASM regimens. The rate of late seizure freedom was similar for patients with or without ASM changes: 21% were seizure-free at the last visit with ASM changes and 19% without ASM changes. There were no significant differences in which ASMs were changed between those who became seizure-free and those who did not, but patients who were subjected to further medical management were less likely to have had mesial temporal sclerosis (MTS) than those who were not. A number of patients not initially seizure-free who underwent ASM changes achieved seizure freedom as long as 10 years post-surgery.

CONCLUSION

A substantial proportion of patients who initially fail epilepsy surgery will have late seizure remission. Those with cavernous hemangiomas were more likely to achieve late remission from seizures as were those with lower rates of seizures in the first year after surgery. The chances of achieving remission were similar in those with or without modification of their ASM regimens, but those with pre-operative MTS were more likely to achieve late seizure freedom without medication changes. At the individual level, patients may still achieve seizure freedom with ASM changes as long as ten years after the initial surgery.

Graph theoretical measures of fast ripples support the epileptic network hypothesis

The epileptic network hypothesis and epileptogenic zone hypothesis are two theories of ictogenesis. The network hypothesis posits that coordinated activity among interconnected nodes produces seizures. The epileptogenic zone hypothesis posits that distinct regions are necessary and sufficient for seizure generation. High-frequency oscillations, and particularly fast ripples, are thought to be biomarkers of the epileptogenic zone. We sought to test these theories by comparing high-frequency oscillation rates and networks in surgical responders and non-responders, with no appreciable change in seizure frequency or severity, within a retrospective cohort of 48 patients implanted with stereo-EEG electrodes. We recorded inter-ictal activity during non-rapid eye movement sleep and semi-automatically detected and quantified high-frequency oscillations. Each electrode contact was localized in normalized coordinates. We found that the accuracy of seizure onset zone electrode contact classification using high-frequency oscillation rates was not significantly different in surgical responders and non-responders, suggesting that in non-responders the epileptogenic zone partially encompassed the seizure onset zone(s) (P > 0.05). We also found that in the responders, fast ripple on oscillations exhibited a higher spectral content in the seizure onset zone compared with the non-seizure onset zone (P < 1 × 10⁻⁵). By contrast, in the non-responders, fast ripple had a lower spectral content in the seizure onset zone (P < 1 × 10⁻⁵). We constructed two different networks of fast ripple with a spectral content >350 Hz. The first was a rate–distance network that multiplied the Euclidian distance between fast ripple-generating contacts by the average rate of fast ripple in the two contacts. The radius of the rate–distance network, which excluded seizure onset zone nodes, discriminated non-responders, including patients not offered resection or responsive neurostimulation due to diffuse multifocal onsets, with an accuracy of 0.77 [95% confidence interval (CI) 0.56–0.98]. The second fast ripple network was constructed using the mutual information between the timing of the events to measure functional connectivity. For most non-responders, this network had a longer characteristic path length, lower mean local efficiency in the non-seizure onset zone, and a higher nodal strength among non-seizure onset zone nodes relative to seizure onset zone nodes. The graphical theoretical measures from the rate–distance and mutual information networks of 22 non- responsive neurostimulation treated patients was used to train a support vector machine, which when tested on 13 distinct patients classified non-responders with an accuracy of 0.92 (95% CI 0.75–1). These results indicate patients who do not respond to surgery or those not selected for resection or responsive neurostimulation can be explained by the epileptic network hypothesis that is a decentralized network consisting of widely distributed, hyperexcitable fast ripple-generating nodes.

Surgery procedures in temporal lobe epilepsies

Temporal lobe epilepsy (TLE) is the most common cause of refractory epilepsy amenable for surgical treatment and seizure control. Surgery for TLE is a safe and effective strategy. The seizure-free rate after surgical resection in patients with mesial or neocortical TLE is about 70%. Resective surgery has an advantage over stereotactic radiosurgery in terms of seizure outcomes for mesial TLE patients. Both techniques have similar results for safety, cognitive outcomes, and associated costs. Stereotactic radiosurgery should therefore be seen as an alternative to open surgery for patients with contraindications for or with reluctance to undergo open surgery. Laser interstitial thermal therapy (LITT) has also shown promising results as a curative technique in mesial TLE but needs to be more deeply evaluated. Brain-responsive stimulation represents a palliative treatment option for patients with unilateral or bilateral MTLE who are not candidates for temporal lobectomy or who have failed a prior mesial temporal lobe resection. Overall, despite the expansion of innovative techniques in recent years, resective surgery remains the reference treatment for TLE and should be proposed as the first-line surgical modality. In the future, ultrasound therapies could become a credible therapeutic option for refractory TLE patients.

Multimodal Image Integration for Epilepsy Presurgical Evaluation: A Clinical Workflow

Multimodal image integration (MMII) is a promising tool to help delineate the epileptogenic zone (EZ) in patients with medically intractable focal epilepsies undergoing presurgical evaluation. We report here the detailed methodology of MMII and an overview of the utility of MMII at the Cleveland Clinic Epilepsy Center from 2014 to 2018, exemplified by illustrative cases. The image integration was performed using the Curry platform (Compumedics Neuroscan^™, Charlotte, NC, USA), including all available diagnostic modalities such as Magnetic resonance imaging (MRI), Positron Emission Tomography (PET), single-photon emission computed tomography (SPECT) and Magnetoencephalography (MEG), with additional capability of trajectory planning for intracranial EEG (ICEEG), particularly stereo-EEG (SEEG), as well as surgical resection planning. In the 5-year time span, 467 patients underwent MMII; of them, 98 patients (21%) had a history of prior neurosurgery and recurring seizures. Of the 467 patients, 425 patients underwent ICEEG implantation with further CT co-registration to identify the electrode locations. A total of 351 patients eventually underwent surgery after MMII, including 197 patients (56%) with non-lesional MRI and 223 patients (64%) with extra-temporal lobe epilepsy. Among 269 patients with 1-year post-operative follow up, 134 patients (50%) had remained completely seizure-free. The most common histopathological finding is focal cortical dysplasia. Our study illustrates the usefulness of MMII to enhance SEEG electrode trajectory planning, assist non-invasive/invasive data interpretation, plan resection strategy, and re-evaluate surgical failures. Information presented by MMII is essential to the understanding of the anatomo-functional-electro-clinical correlations in individual cases, which leads to the ultimate success of presurgical evaluation of patients with medically intractable focal epilepsies.

Response to antiepileptic drugs after unsuccessful epilepsy surgery: A multivariate analysis of 103 patients

OBJECT

Epilepsy patients may still have seizures after surgery, and there have been few studies on the response to antiepileptic drugs (AEDs) after surgery failure. The purpose of this study was to analyze the response to AEDs after unsuccessful epilepsy surgery.

METHODS

Patients who underwent unsuccessful epilepsy surgery between January 1999 and January 2019 were evaluated. Patient demographics, etiology, factors related to surgery and AED use patterns were assessed.

RESULTS

After excluding the 5 patients who were lost to follow-up and the 2 patients who died, the records of 103 consecutive patients were analyzed. Ninety patients (87.4 %) had seizure recurrence within one year after surgery, 2 (1.9 %) patients had recurrence from one year to two years after surgery, and 11 (10.7 %) patients had recurrence two or more years after surgery (2-10 years). After surgery failure, the patients tried at least 2 kinds of AEDs with different mechanisms for more than 2 years. The average total number of AEDs used was 5.97, the average number of AEDs used before surgery was 3.21, and the average number of AEDs used after surgery was 4.02. After retreatment with AEDs, 10 patients (9.7 %) were seizure-free, 18 patients' (17.5 %) seizures were alleviated, and 75 patients (72.8 %) had seizures as they did prior to the adjustments. The number of AEDs used before and after surgery and the total number of AEDs were not significantly different among the seizure free group, alleviated seizure group and no change group. There were no significant differences in seizure onset age, surgery age, etiology, time between seizure onset and surgery, magnetic resonance imaging, seizure type, localization and lateralization of the surgery site among the three groups.

CONCLUSIONS

The results showed that a small percentage of patients (27.2 %) who undergo unsuccessful epilepsy surgery benefit from AED adjustments; however, the vast majority of patients (72.8 %) do not benefit from AED adjustments.

Aggressive cytoreduction and multiple subpial cortical transections may obtain good surgical outcomes in refractory epilepsy with multiple epileptic foci

Backgrounds

Epilepsy surgery is the most efficacious therapeutic modality for patients with medical refractory epilepsy, especially resective surgery. However, the variable etiologies and multiple epileptic foci are usually associated with the outcomes. The aim of this study was to demonstrate that combination of different intervention procedures might be an alternative option for patients of refractory epilepsy.

Methods

We retrospectively analyzed pre-operative and post-surgical outcomes in 30 patients who received epilepsy surgery between January 1, 2010 and December 31, 2014 at Chang Gung Memorial Hospital (CGMH), Linkou, according to Engel's classification.

Results

Twenty-six of the 30 patients (86.7%) had good outcomes, sum of class I and class II after epilepsy surgery. The good outcome rate of our complicated group was 80.0% (12/15), compared to 93.3% (14/15) in the simple group, but no significant differences between the two groups (p = 0.569). Four patients whose epileptic foci involved eloquent area and received multiple subpial cortical transection, and good outcome rate was 75% (3/4). At last, six patients had previously failed epilepsy surgery and received a reoperation, with a good outcome rate of 83.3% (5/6).

Conclusion

After complete pre-surgical evaluation and combined interventional procedures, the patients with refractory epilepsy had satisfactory outcomes and few neurological complications. Moreover, re-operation can improve the outcome in some patients who previously failed epilepsy surgery.

Rates and predictors of success and failure in repeat epilepsy surgery: A meta-analysis and systematic review

OBJECTIVE

Medically refractory epilepsy is a debilitating disorder that is particularly challenging to treat in patients who have already failed a surgical resection. Evidence regarding outcomes of further epilepsy surgery is limited to small case series and reviews. Therefore, our group performed the first quantitative meta-analysis of the literature from the past 30 years to assess for rates and predictors of successful reoperations.

METHODS

A PubMed search was conducted for studies reporting outcomes of repeat epilepsy surgery. Studies were excluded if they reported fewer than five eligible patients or had average follow-ups < 1 year, and patients were excluded from analysis if they received a nonresective intervention. Outcomes were stratified by each variable of interest, and quantitative meta-analysis was performed to generate odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Seven hundred eighty-two patients who received repeat resective epilepsy surgery from 36 studies were included. Engel I outcome was observed in 47% (n = 369) of patients. Significant predictors of seizure freedom included congruent over noncongruent electrophysiology data (OR = 3.6, 95% CI = 1.6-8.2), lesional over nonlesional epilepsy (OR = 3.2, 95% CI = 1.9-5.3), and surgical limitations over disease-related factors associated with failure of the first surgery (OR = 2.6, 95% CI = 1.3-5.3). Among patients with at least one of these predictors, seizure freedom was achieved in 58%. Conversely, the use of invasive monitoring was associated with worse outcome (OR = 0.4, 95% CI = 0.2-0.9). Temporal lobe over extratemporal/multilobe resection (OR = 1.5, 95% CI = 0.8-3.0) and abnormal over normal preoperative magnetic resonance imaging (OR = 1.9, 95% CI = 0.6-5.4) showed nonsignificant trends toward seizure freedom.

SIGNIFICANCE

This analysis supports considering further resection in patients with intractable epilepsy who continue to have debilitating seizures after an initial surgery, especially in the context of factors predictive of a favorable outcome.

Autonomic Regulation Therapy in Heart Failure

Autonomic regulation therapy (ART) is a rapidly emerging therapy in the management of congestive heart failure secondary to systolic dysfunction. Modulation of the cardiac neuronal hierarchy can be achieved with bioelectronics modulation of the spinal cord, cervical vagus, baroreceptor, or renal nerve ablation. This review will discuss relevant preclinical and clinical research in ART for systolic heart failure. Understanding mechanistically what is being stimulated within the autonomic nervous system by such device-based therapy and how the system reacts to such stimuli is essential for optimizing stimulation parameters and for the future development of effective ART.