Long term outcome in patients not initially seizure free after resective epilepsy surgery

Kindling in humans: Does secondary epileptogenesis occur?

The relevance of secondary epileptogenesis for human epilepsy remains a controversial subject decades after it was first described in animal models. Whether or not a previously normal brain region can become independently epileptogenic through a kindling-like process has not, and cannot, be definitely proven in humans. Rather than reliance on direct experimental evidence, attempts to answering this question must depend on observational data. In this review, observations based largely upon contemporary surgical series will advance the case for secondary epileptogenesis in humans. As will be argued, hypothalamic hamartoma-related epilepsy provides the strongest case for this process; all the stages of secondary epileptogenesis can be observed. Hippocampal sclerosis (HS) is another pathology where the question of secondary epileptogenesis frequently arises, and observations from bitemporal and dual pathology series are explored. The verdict here is far more difficult to reach, in large part because of the scarcity of longitudinal cohorts; moreover, recent experimental data have challenged the claim that HS is acquired consequent to recurrent seizures. Synaptic plasticity more than seizure-induced neuronal injury is the likely mechanism of secondary epileptogenesis. Postoperative running-down phenomenon provides the best evidence that a kindling-like process occurs in some patients, evidenced by its reversal. Finally, a network perspective of secondary epileptogenesis is considered, as well as the possible role for subcortical surgical interventions.

Epileptic seizure focus detection from interictal electroencephalogram: a survey

Electroencephalogram (EEG) is one of most effective clinical diagnosis modalities for the localization of epileptic focus. Most current AI solutions use this modality to analyze the EEG signals in an automated manner to identify the epileptic seizure focus. To develop AI system for identifying the epileptic focus, there are many recently-published AI solutions based on biomarkers or statistic features that utilize interictal EEGs. In this review, we survey these solutions and find that they can be divided into three main categories: (i) those that use of biomarkers in EEG signals, including high-frequency oscillation, phase-amplitude coupling, and interictal epileptiform discharges, (ii) others that utilize feature-extraction methods, and (iii) solutions based upon neural networks (an end-to-end approach). We provide a detailed description of seizure focus with clinical diagnosis methods, a summary of the public datasets that seek to reduce the research gap in epilepsy, recent novel performance evaluation criteria used to evaluate the AI systems, and guidelines on when and how to use them. This review also suggests a number of future research challenges that must be overcome in order to design more efficient computer-aided solutions to epilepsy focus detection.

The localization and lateralization of fear aura and its surgical prognostic value in patients with focal epilepsy

OBJECTIVE

Fear aura has traditionally been considered relevant to epileptic discharges from mesial temporal areas, and few studies have investigated its effect on surgical outcome in drug-resistant epilepsy. We aim to assess the localizing and lateralizing value as well as prognostic significance of fear aura in patients with focal epilepsy.

METHODS

The occurrence of fear aura in relation to epileptogenic origin and its association with postoperative outcome were analyzed in 146 consecutive patients undergoing resective surgery for intractable epilepsy.

RESULTS

Ninety-four (64.4%) patients reported auras, and 31 (21.2%) reported fear aura in their seizures. One hundred ten (75.3%) patients had an Engel class I outcome until last follow-up, of whom 24 experienced fear aura preoperatively. Fear aura appeared more frequently during temporal and frontal lobe seizures, but did not lateralize the seizure onset zone. There were no significant baseline differences between patients with and without fear aura. No correlation was found between postoperative outcome and the presence of auras. Occurrence of fear aura failed to show predictive value in surgical outcome whether in pooled or subgroup analysis.

INTERPRETATION

This study advances our understanding of the origin of fear aura, and is helpful for presurgical evaluation and outcome prediction. Without lateralizing value, fear aura is more commonly seen with temporal or frontal origin. When taken as a whole, auras do not have a significant impact on seizure outcome in focal epilepsy. Patients with fear aura are no more likely to become seizure-free than those without fear aura.

Outcome of epilepsy surgery in lesional epilepsy: Experiences from a developing country

BACKGROUND

Our aim was to report the postoperative seizure outcome and associated factors in patients with lesional epilepsy, in a low-income setting.

METHODS

This longitudinal prospective study included patients who underwent epilepsy surgery at Kashani Comprehensive Epilepsy Center between 2014 and 2019. Post-surgical outcomes were reported according to the Engel score, and patients were classified into two groups of seizure free (SF) and not-seizure free (NSF).

RESULTS

A total of 148 adult patients, with a mean age of 30.45 ± 9.23 years were included. The SF outcome was reported in 86.5% of patients and antiepileptic drugs (AEDs) were reduced or discontinued in 45.9%. The mean follow-up duration was 26.7 ± 14.9 months. Temporal lobe lesions (76.3%) and mesial temporal sclerosis (MTS) (56.7%) were the most frequent etiologies. Temporal lesion (Incidence relative risk (IRR): 1.76, 95% CI [1.08-2.87], p = 0.023), prior history of CNS infection (IRR:1.18, 95% CI [1.03-1.35], p = 0.019), use of intra-operative ECoG (IRR:1.73, 95% CI [1.06-2.81], p = 0.028), and absence of IEDs in postoperative EEG (IRR: 1.41, 95% CI [1.18-1.70], p < 0.001) were positive predictors for a favorable outcome.

CONCLUSION

Many patients with drug-resistant lesional epilepsy showed a favorable response to surgery. We believe that resective epilepsy surgery in low-income settings is a major treatment option. The high frequency of patients with drug-resistant epilepsy in developing countries is associated with high rates of morbidity and mortality. Hence, strategies to increase access to epilepsy surgery in these settings are urgently needed.

Surgery for epilepsy

BACKGROUND

This is an updated version of the original Cochrane review, published in 2015.Focal epilepsies are caused by a malfunction of nerve cells localised in one part of one cerebral hemisphere. In studies, estimates of the number of individuals with focal epilepsy who do not become seizure-free despite optimal drug therapy vary between at least 20% and up to 70%. If the epileptogenic zone can be located, surgical resection offers the chance of a cure with a corresponding increase in quality of life.

OBJECTIVES

The primary objective is to assess the overall outcome of epilepsy surgery according to evidence from randomised controlled trials.Secondary objectives are to assess the overall outcome of epilepsy surgery according to non-randomised evidence, and to identify the factors that correlate with remission of seizures postoperatively.

SEARCH METHODS

For the latest update, we searched the following databases on 11 March 2019: Cochrane Register of Studies (CRS Web), which includes the Cochrane Epilepsy Group Specialized Register and the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE (Ovid, 1946 to March 08, 2019), ClinicalTrials.gov, and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP).

SELECTION CRITERIA

Eligible studies were randomised controlled trials (RCTs) that included at least 30 participants in a well-defined population (age, sex, seizure type/frequency, duration of epilepsy, aetiology, magnetic resonance imaging (MRI) diagnosis, surgical findings), with an MRI performed in at least 90% of cases and an expected duration of follow-up of at least one year, and reporting an outcome related to postoperative seizure control. Cohort studies or case series were included in the previous version of this review.

DATA COLLECTION AND ANALYSIS

Three groups of two review authors independently screened all references for eligibility, assessed study quality and risk of bias, and extracted data. Outcomes were proportions of participants achieving a good outcome according to the presence or absence of each prognostic factor of interest. We intended to combine data with risk ratios (RRs) and 95% confidence intervals (95% CIs).

MAIN RESULTS

We identified 182 studies with a total of 16,855 included participants investigating outcomes of surgery for epilepsy. Nine studies were RCTs (including two that randomised participants to surgery or medical treatment (99 participants included in the two trials received medical treatment)). Risk of bias in these RCTs was unclear or high. Most of the remaining 173 non-randomised studies followed a retrospective design. We assessed study quality using the Effective Public Health Practice Project (EPHPP) tool and determined that most studies provided moderate or weak evidence. For 29 studies reporting multivariate analyses, we used the Quality in Prognostic Studies (QUIPS) tool and determined that very few studies were at low risk of bias across domains.In terms of freedom from seizures, two RCTs found surgery (n = 97) to be superior to medical treatment (n = 99); four found no statistically significant differences between anterior temporal lobectomy (ATL) with or without corpus callosotomy (n = 60), between subtemporal or transsylvian approach to selective amygdalohippocampectomy (SAH) (n = 47); between ATL, SAH and parahippocampectomy (n = 43) or between 2.5 cm and 3.5 cm ATL resection (n = 207). One RCT found total hippocampectomy to be superior to partial hippocampectomy (n = 70) and one found ATL to be superior to stereotactic radiosurgery (n = 58); and another provided data to show that for Lennox-Gastaut syndrome, no significant differences in seizure outcomes were evident between those treated with resection of the epileptogenic zone and those treated with resection of the epileptogenic zone plus corpus callosotomy (n = 43). We judged evidence from the nine RCTs to be of moderate to very low quality due to lack of information reported about the randomised trial design and the restricted study populations.Of the 16,756 participants included in this review who underwent a surgical procedure, 10,696 (64%) achieved a good outcome from surgery; this ranged across studies from 13.5% to 92.5%. Overall, we found the quality of data in relation to recording of adverse events to be very poor.In total, 120 studies examined between one and eight prognostic factors in univariate analysis. We found the following prognostic factors to be associated with a better post-surgical seizure outcome: abnormal pre-operative MRI, no use of intracranial monitoring, complete surgical resection, presence of mesial temporal sclerosis, concordance of pre-operative MRI and electroencephalography, history of febrile seizures, absence of focal cortical dysplasia/malformation of cortical development, presence of tumour, right-sided resection, and presence of unilateral interictal spikes. We found no evidence that history of head injury, presence of encephalomalacia, presence of vascular malformation, and presence of postoperative discharges were prognostic factors of outcome.Twenty-nine studies reported multi-variable models of prognostic factors, and showed that the direction of association of factors with outcomes was generally the same as that found in univariate analyses.We observed variability in many of our analyses, likely due to small study sizes with unbalanced group sizes and variation in the definition of seizure outcome, the definition of prognostic factors, and the influence of the site of surgery AUTHORS' CONCLUSIONS: Study design issues and limited information presented in the included studies mean that our results provide limited evidence to aid patient selection for surgery and prediction of likely surgical outcomes. Future research should be of high quality, follow a prospective design, be appropriately powered, and focus on specific issues related to diagnostic tools, the site-specific surgical approach, and other issues such as extent of resection. Researchers should investigate prognostic factors related to the outcome of surgery via multi-variable statistical regression modelling, where variables are selected for modelling according to clinical relevance, and all numerical results of the prognostic models are fully reported. Journal editors should not accept papers for which study authors did not record adverse events from a medical intervention. Researchers have achieved improvements in cancer care over the past three to four decades by answering well-defined questions through the conduct of focused RCTs in a step-wise fashion. The same approach to surgery for epilepsy is required.

Preoperative prediction of temporal lobe epilepsy surgery outcome

PURPOSE

There is controversy about relative contributions of ictal scalp video EEG recording (vEEG), routine scalp outpatient interictal EEG (rEEG), intracranial EEG (iEEG) and MRI for predicting seizure-free outcomes after temporal lobectomy. We reviewed NIH experience to determine contributions at specific time points as well as long-term predictive value of standard pre-surgical investigations.

METHODS

Raw data was obtained via retrospective chart review of 151 patients. After exclusions, 118 remained (median 5 years follow-up). MRI-proven mesial temporal sclerosis (MTSr) was considered a separate category for analysis. Logistic regression estimated odds ratios at 6-months, 1-year, and 2 years; proportional hazard models estimated long-term comparisons. Subset analysis of the proportional hazard model was performed including only patients with commonly encountered situations in each of the modalities, to maximize statistical inference.

RESULTS

Any MRI finding, MRI proven MTS, rEEG, vEEG and iEEG did not predict two-year seizure-free outcome. MTSr was predictive at six months (OR=2.894, p=0. 0466), as were MRI and MTSr at one year (OR=10.4231, p=0. 0144 and OR=3.576, p=0. 0091). Correcting for rEEG and MRI, vEEG failed to predict outcome at 6 months, 1year and 2 years. Proportional hazard analysis including all available follow-up failed to achieve significance for any modality. In the subset analysis of 83 patients with commonly encountered results, vEEG modestly predicted long-term seizure-free outcomes with a proportional hazard ratio of 1.936 (p=0.0304).

CONCLUSIONS

In this study, presurgical tools did not provide unambiguous long-term outcome predictions. Multicenter prospective studies are needed to determine optimal presurgical epilepsy evaluation.

Surgery for epilepsy

BACKGROUND

Focal epilepsies are caused by a malfunction of nerve cells localised in one part of one cerebral hemisphere. In studies, estimates of the number of individuals with focal epilepsy who do not become seizure-free despite optimal drug therapy vary according to the age of the participants and which focal epilepsies are included, but have been reported as at least 20% and in some studies up to 70%. If the epileptogenic zone can be located surgical resection offers the chance of a cure with a corresponding increase in quality of life.

OBJECTIVES

The primary objective is to assess the overall outcome of epilepsy surgery according to evidence from randomised controlled trials.The secondary objectives are to assess the overall outcome of epilepsy surgery according to non-randomised evidence and to identify the factors that correlate to remission of seizures postoperatively.

SEARCH METHODS

We searched the Cochrane Epilepsy Group Specialised Register (June 2013), the Cochrane Central Register of Controlled Trials (CENTRAL 2013, Issue 6), MEDLINE (Ovid) (2001 to 4 July 2013), ClinicalTrials.gov and the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) for relevant trials up to 4 July 2013.

SELECTION CRITERIA

Eligible studies were randomised controlled trials (RCTs), cohort studies or case series, with either a prospective and/or retrospective design, including at least 30 participants, a well-defined population (age, sex, seizure type/frequency, duration of epilepsy, aetiology, magnetic resonance imaging (MRI) diagnosis, surgical findings), an MRI performed in at least 90% of cases and an expected duration of follow-up of at least one year, and reporting an outcome relating to postoperative seizure control.

DATA COLLECTION AND ANALYSIS

Three groups of two review authors independently screened all references for eligibility, assessed study quality and risk of bias, and extracted data. Outcomes were proportion of participants achieving a good outcome according to the presence or absence of each prognostic factor of interest. We intended to combine data with risk ratios (RR) and 95% confidence intervals.

MAIN RESULTS

We identified 177 studies (16,253 participants) investigating the outcome of surgery for epilepsy. Four studies were RCTs (including one that randomised participants to surgery or medical treatment). The risk of bias in the RCTs was unclear or high, limiting our confidence in the evidence that addressed the primary review objective. Most of the remaining 173 non-randomised studies had a retrospective design; they were of variable size, were conducted in a range of countries, recruited a wide demographic range of participants, used a wide range of surgical techniques and used different scales used to measure outcomes. We performed quality assessment using the Effective Public Health Practice Project (EPHPP) tool and determined that most studies provided moderate or weak evidence. For 29 studies reporting multivariate analyses we used the Quality in Prognostic Studies (QUIPS) tool and determined that very few studies were at low risk of bias across the domains.In terms of freedom from seizures, one RCT found surgery to be superior to medical treatment, two RCTs found no statistically significant difference between anterior temporal lobectomy (ATL) with or without corpus callosotomy or between 2.5 cm or 3.5 cm ATL resection, and one RCT found total hippocampectomy to be superior to partial hippocampectomy. We judged the evidence from the four RCTs to be of moderate to very low quality due to the lack of information reported about the randomised trial design and the restricted study populations.Of the 16,253 participants included in this review, 10,518 (65%) achieved a good outcome from surgery; this ranged across studies from 13.5% to 92.5%. Overall, we found the quality of data in relation to the recording of adverse events to be very poor.In total, 118 studies examined between one and eight prognostic factors in univariate analysis. We found the following prognostic factors to be associated with a better post-surgical seizure outcome: an abnormal pre-operative MRI, no use of intracranial monitoring, complete surgical resection, presence of mesial temporal sclerosis, concordance of pre-operative MRI and electroencephalography (EEG), history of febrile seizures, absence of focal cortical dysplasia/malformation of cortical development, presence of tumour, right-sided resection and presence of unilateral interictal spikes. We found no evidence that history of head injury, presence of encephalomalacia, presence of vascular malformation or presence of postoperative discharges were prognostic factors of outcome. We observed variability between studies for many of our analyses, likely due to the small study sizes with unbalanced group sizes, variation in the definition of seizure outcome, definition of the prognostic factor and the influence of the site of surgery, all of which we observed to be related to postoperative seizure outcome. Twenty-nine studies reported multivariable models of prognostic factors and the direction of association of factors with outcome was generally the same as found in the univariate analyses. However, due to the different multivariable analysis approaches and selective reporting of results, meaningful comparison of multivariate analysis with univariate meta-analysis is difficult.

AUTHORS' CONCLUSIONS

The study design issues and limited information presented in the included studies mean that our results provide limited evidence to aid patient selection for surgery and prediction of likely surgical outcome. Future research should be of high quality, have a prospective design, be appropriately powered and focus on specific issues related to diagnostic tools, the site-specific surgical approach and other issues such as the extent of resection. Prognostic factors related to the outcome of surgery should be investigated via multivariable statistical regression modelling, where variables are selected for modelling according to clinical relevance and all numerical results of the prognostic models are fully reported. Protocols should include pre- and postoperative measures of speech and language function, cognition and social functioning along with a mental state assessment. Journal editors should not accept papers where adverse events from a medical intervention are not recorded. Improvements in the development of cancer care over the past three to four decades have been achieved by answering well-defined questions through the conduct of focused RCTs in a step-wise fashion. The same approach to surgery for epilepsy is required.

Long-term outcome and predictors of resective surgery prognosis in patients with refractory extratemporal epilepsy

PURPOSE

We analyzed the long-term postoperative outcome and possible predictive factors of the outcome in surgically treated patients with refractory extratemporal epilepsy.

METHODS

We retrospectively analyzed 73 patients who had undergone resective surgery at the Epilepsy Center Brno between 1995 and 2010 and who had reached at least 1 year outcome after the surgery. The average age at surgery was 28.3±11.4 years. Magnetic resonance imaging (MRI) did not reveal any lesion in 24 patients (32.9%). Surgical outcome was assessed annually using Engel's modified classification until 5 years after surgery and at the latest follow-up visit.

RESULTS

Following the surgery, Engel Class I outcome was found in 52.1% of patients after 1 year, in 55.0% after 5 years, and in 50.7% at the last follow-up visit (average 6.15±3.84 years). Of the patients who reached the 5-year follow-up visit (average of the last follow-up 9.23 years), 37.5% were classified as Engel IA at each follow-up visit. Tumorous etiology and lesions seen in preoperative MRI were associated with significantly better outcome (p=0.035; p<0.01). Postoperatively, 9.6% patients had permanent neurological deficits.

CONCLUSION

Surgical treatment of refractory extratemporal epilepsy is an effective procedure. The presence of a visible MRI-detected lesion and tumorous etiology is associated with significantly better outcome than the absence of MRI-detected lesion or other etiology.

Pediatric epilepsy surgery: long-term 5-year seizure remission and medication use

BACKGROUND

It is unclear whether long-term seizure outcomes in children are similar to those in adult epilepsy surgery patients.

OBJECTIVE

To determine 5-year outcomes and antiepilepsy drug (AED) use in pediatric epilepsy surgery patients from a single institution.

METHODS

The cohort consisted of children younger than 18 years of age whose 5-year outcome data would have been available by 2010. Comparisons were made between patients with and without 5-year data (n = 338), patients with 5-year data for seizure outcome (n = 257), and seizure-free patients on and off AEDs (n = 137).

RESULTS

Five-year data were available from 76% of patients. More seizure-free patients with focal resections for hippocampal sclerosis and tumors lacked 5-year data compared with other cases. Of those with 5-year data, 53% were continuously seizure free, 18% had late seizure recurrence, 3% became seizure free after initial failure, and 25% were never seizure free. Patients were more likely to be continuously seizure free if their surgery was performed during the period 2001 to 2005 (68%) compared with surgery performed from 1996 to 2000 (61%), 1991 to 1995 (36%), and 1986 to 1990 (46%). More patients had 1 or fewer seizures per month in the late seizure recurrence (47%) compared with the not seizure-free group (20%). Four late deaths occurred in the not seizure-free group compared with 1 in the seizure-free group. Of patients who were continuously seizure free, 55% were not taking AEDs, and more cortical dysplasia patients (74%) had stopped taking AEDs compared with hemimegalencephaly patients (18%).

CONCLUSION

In children, 5-year outcomes improved over 20 years of clinical experience. Our results are similar to those of adult epilepsy surgery patients despite mostly extratemporal and hemispheric operations for diverse developmental etiologies.