Practice parameter: temporal lobe and localized neocortical resections for epilepsy: report of the Quality Standards Subcommittee of the American Academy of Neurology, in association with the American Epilepsy Society and the American Association of Neurological Surgeons

When spikes are symmetric, ripples are not: Bilateral spike and wave above 80 Hz in focal and generalized epilepsy

OBJECTIVE

To evaluate scalp ripples distribution in secondary bilateral synchrony as a tool to lateralize the epileptic focus and to differentiate focal from generalized epilepsy.

METHODS

Seventeen EEG recordings with bilateral synchronous discharges of focal (focal group-FG: 10) and generalized (generalized group-GG: 7) epilepsy patients were selected for spikes and ripples marking; the spike-normalized ripple rate was calculated in each hemisphere (right/left - anterior/posterior) and a ripple-dominant hemisphere (the one with the highest rate) was identified. Concordance in FG between the ripple dominant hemisphere and the hemisphere of clinical lateralization was evaluated. The ripple-dominant/ripple-nondominant spike-normalized ripple rate ratio was studied to compare groups.

RESULTS

In FG the hemisphere of clinical lateralization and the ripple-dominant hemisphere were 100% concordant. In GG only 3/7 patients showed ripples (vs 10/10 FG), all with anterior dominance. No difference in hemisphere ripple dominance between groups was found.

CONCLUSIONS

Ripples in secondary bilateral synchrony help to lateralize the epileptic focus but do not help to differentiate between focal and generalized epilepsy. This is the first report of visually identified ripples in idiopathic generalized epilepsy.

SIGNIFICANCE

Ripples confirm the clinical lateralization of the epileptic focus in secondary bilateral synchrony but cannot distinguish between focal and generalized epilepsy.

Disparities in surgery among patients with intractable epilepsy in a universal health system

OBJECTIVE

To assess the use of epilepsy surgery in patients with medically intractable epilepsy in a publicly funded universal health care system.

METHODS

We performed a population-based retrospective cohort study using linked health care databases for Ontario, Canada, between 2001 and 2010. We identified all patients with medically intractable epilepsy, defined as those with seizures that did not respond to at least 2 adequate trials of seizure medications. We assessed the proportion of patients who had epilepsy surgery within the following 2 years. We further identified the characteristics associated with epilepsy surgery.

RESULTS

A total of 10,661 patients were identified with medically intractable epilepsy (mean age 47 years, 51% male); most (74%) did not have other comorbidities. Within 2 years of being defined as medically intractable, only 124 patients (1.2%) underwent epilepsy surgery. Death occurred in 12% of those with medically intractable epilepsy. Those who underwent the procedure were younger and had fewer comorbidities compared to those who did not.

CONCLUSION

In our setting of publicly funded universal health care, more than 10% of patients died within 2 years of developing medically intractable epilepsy. Epilepsy surgery may be an effective treatment for some patients; however, fewer than 2% of patients who may have benefited from epilepsy surgery received it.

Neuromodulation for Epilepsy

Several palliative neuromodulation treatment modalities are currently available for adjunctive use in the treatment of medically intractable epilepsy. Over the past decades, a variety of different central and peripheral nervous system sites have been identified, clinically and experimentally, as potential targets for chronic, nonresponsive therapeutic neurostimulation. Currently, the main modalities in clinical use, from most invasive to least invasive, are anterior thalamus deep brain stimulation, vagus nerve stimulation, and trigeminal nerve stimulation. Significant reductions in seizure frequency have been demonstrated in clinical trials using each of these neuromodulation therapies.

Human brain slices for epilepsy research: Pitfalls, solutions and future challenges

Increasingly, neuroscientists are taking the opportunity to use live human tissue obtained from elective neurosurgical procedures for electrophysiological studies in vitro. Access to this valuable resource permits unique studies into the network dynamics that contribute to the generation of pathological electrical activity in the human epileptic brain. Whilst this approach has provided insights into the mechanistic features of electrophysiological patterns associated with human epilepsy, it is not without technical and methodological challenges. This review outlines the main difficulties associated with working with epileptic human brain slices from the point of collection, through the stages of preparation, storage and recording. Moreover, it outlines the limitations, in terms of the nature of epileptic activity that can be observed in such tissue, in particular, the rarity of spontaneous ictal discharges, we discuss manipulations that can be utilised to induce such activity. In addition to discussing conventional electrophysiological techniques that are routinely employed in epileptic human brain slices, we review how imaging and multielectrode array recordings could provide novel insights into the network dynamics of human epileptogenesis. Acute studies in human brain slices are ultimately limited by the lifetime of the tissue so overcoming this issue provides increased opportunity for information gain. We review the literature with respect to organotypic culture techniques that may hold the key to prolonging the viability of this material. A combination of long-term culture techniques, viral transduction approaches and electrophysiology in human brain slices promotes the possibility of large scale monitoring and manipulation of neuronal activity in epileptic microcircuits.

Non-pharmacological interventions for people with epilepsy and intellectual disabilities

BACKGROUND

Approximately 30% of patients with epilepsy remain refractory to drug treatment and continue to experience seizures whilst taking one or more antiepileptic drugs (AEDs). Several non-pharmacological interventions that may be used in conjunction with or as an alternative to AEDs are available for refractory patients. In view of the fact that seizures in people with intellectual disabilities are often complex and refractory to pharmacological interventions, it is evident that good quality randomised controlled trials (RCTs) are needed to assess the efficacy of alternatives or adjuncts to pharmacological interventions.This is an updated version of the original Cochrane review (Beavis 2007) published in The Cochrane Library (2007, Issue 4).

OBJECTIVES

To assess data derived from randomised controlled trials of non-pharmacological interventions for people with epilepsy and intellectual disabilities.Non-pharmacological interventions include, but are not limited to, the following.• Surgical procedures.• Specialised diets, for example, the ketogenic diet, or vitamin and folic acid supplementation.• Psychological interventions for patients or for patients and carers/parents, for example, cognitive-behavioural therapy (CBT), electroencephalographic (EEG) biofeedback and educational intervention.• Yoga.• Acupuncture.• Relaxation therapy (e.g. music therapy).

SEARCH METHODS

For the latest update of this review, we searched the Cochrane Epilepsy Group Specialised Register (19 August 2014), the Cochrane Central Register of Controlled Trials (CENTRAL) via CRSO (19 August 2014), MEDLINE (Ovid, 1946 to 19 August 2014) and PsycINFO (EBSCOhost, 1887 to 19 August 2014).

SELECTION CRITERIA

Randomised controlled trials of non-pharmacological interventions for people with epilepsy and intellectual disabilities.

DATA COLLECTION AND ANALYSIS

Two review authors independently applied the inclusion criteria and extracted study data.

MAIN RESULTS

One study is included in this review. When two surgical procedures were compared, results indicated that corpus callosotomy with anterior temporal lobectomy was more effective than anterior temporal lobectomy alone in improving quality of life and performance on IQ tests among people with epilepsy and intellectual disabilities. No evidence was found to support superior benefit in seizure control for either intervention. This is the only study of its kind and was rated as having an overall unclear risk of bias. The previous update (December 2010) identified one RCT in progress. The study authors have confirmed that they are aiming to publish by the end of 2015; therefore this study (Bjurulf 2008) has not been included in the current review.

AUTHORS' CONCLUSIONS

This review highlights the need for well-designed randomised controlled trials conducted to assess the effects of non-pharmacological interventions on seizure and behavioural outcomes in people with intellectual disabilities and epilepsy.

Hippocampal closed-loop modeling and implications for seizure stimulation design

OBJECTIVE

Traditional hippocampal modeling has focused on the series of feedforward synapses known as the trisynaptic pathway. However, feedback connections from CA1 back to the hippocampus through the entorhinal cortex (EC) actually make the hippocampus a closed-loop system. By constructing a functional closed-loop model of the hippocampus, one may learn how both physiological and epileptic oscillations emerge and design efficient neurostimulation patterns to abate such oscillations.

APPROACH

Point process input-output models where estimated from recorded rodent hippocampal data to describe the nonlinear dynamical transformation from CA3 → CA1, via the schaffer-collateral synapse, and CA1 → CA3 via the EC. Each Volterra-like subsystem was composed of linear dynamics (principal dynamic modes) followed by static nonlinearities. The two subsystems were then wired together to produce the full closed-loop model of the hippocampus.

MAIN RESULTS

Closed-loop connectivity was found to be necessary for the emergence of theta resonances as seen in recorded data, thus validating the model. The model was then used to identify frequency parameters for the design of neurostimulation patterns to abate seizures.

SIGNIFICANCE

Deep-brain stimulation (DBS) is a new and promising therapy for intractable seizures. Currently, there is no efficient way to determine optimal frequency parameters for DBS, or even whether periodic or broadband stimuli are optimal. Data-based computational models have the potential to be used as a testbed for designing optimal DBS patterns for individual patients. However, in order for these models to be successful they must incorporate the complex closed-loop structure of the seizure focus. This study serves as a proof-of-concept of using such models to design efficient personalized DBS patterns for epilepsy.

Slow Spatial Recruitment of Neocortex during Secondarily Generalized Seizures and Its Relation to Surgical Outcome

Understanding the spatiotemporal dynamics of brain activity is crucial for inferring the underlying synaptic and nonsynaptic mechanisms of brain dysfunction. Focal seizures with secondary generalization are traditionally considered to begin in a limited spatial region and spread to connected areas, which can include both pathological and normal brain tissue. The mechanisms underlying this spread are important to our understanding of seizures and to improve therapies for surgical intervention. Here we study the properties of seizure recruitment-how electrical brain activity transitions to large voltage fluctuations characteristic of spike-and-wave seizures. We do so using invasive subdural electrode arrays from a population of 16 patients with pharmacoresistant epilepsy. We find an average delay of ∼30 s for a broad area of cortex (8 × 8 cm) to be recruited into the seizure, at an estimated speed of ∼4 mm/s. The spatiotemporal characteristics of recruitment reveal two categories of patients: one in which seizure recruitment of neighboring cortical regions follows a spatially organized pattern consistent from seizure to seizure, and a second group without consistent spatial organization of activity during recruitment. The consistent, organized recruitment correlates with a more regular, compared with small-world, connectivity pattern in simulation and successful surgical treatment of epilepsy. We propose that an improved understanding of how the seizure recruits brain regions into large amplitude voltage fluctuations provides novel information to improve surgical treatment of epilepsy and highlights the slow spread of massive local activity across a vast extent of cortex during seizure.

Systematic review of the efficacy in seizure control and safety of neuronavigation in epilepsy surgery: The need for well-designed prospective studies

PURPOSE

To evaluate the efficacy of surgery with neuronavigation compared to conventional neurosurgical treatment of epilepsy in terms of safety and seizure outcomes and to assess the quality of the evidence base of neuronavigation in this clinical context.

METHOD

Systematic review using the electronic databases of Cochrane, CRD, PubMed, Embase, SciELO and LILACS in Portuguese, English and Spanish. The [MeSH] terms included "epilepsy" and "neuronavigation".

ELIGIBILITY CRITERIA

Studies assessing surgery with neuronavigation for the surgical treatment of epilepsy or brain injuries associated with epileptic seizures.

RESULTS

We identified 28 original articles. All articles yielded scientific evidence of low quality. Outcome data presented in the articles identified was heterogeneous and did not amount to compelling evidence that epilepsy surgery with neuronavigation produces higher rates of seizure control, a reduced need for reoperations, or lower rates of complications or postoperative neurological deficits.

CONCLUSION

We were unable to find any publications providing convincing evidence that neuronavigation improves outcomes of epilepsy surgery. Whilst this does not mean that neuronavigation cannot improve neurosurgical outcomes in this clinical setting, well-designed research studies evaluating the role of neuronavigation are urgently needed.

Brain tumors in children with refractory seizures—a long-term follow-up study after epilepsy surgery

PURPOSE

Epilepsy surgery is an established treatment option for medically refractory epilepsy. Brain tumors, besides dysplasias, vascular malformations, and other lesions, can cause refractory epilepsy. Long-term epilepsy-associated brain tumors, even though mostly benign, are neoplastic lesions and thus have to be considered as both epileptic and oncological lesions.

METHODS

We retrospectively analyzed epileptological and oncological long-term follow-up (FU) in pediatric patients who underwent brain surgery for refractory epilepsy and whose histology showed a tumor as underlying cause (n = 107, mean FU 119 months).

RESULTS

At last available outcome, 82.2% of patients were seizure free (International League Against Epilepsy (ILAE) class 1) and seizure outcome was stable over more than 14 years. Fifty-four percent of the patients were without anti-epileptic drugs (AEDs) at last available outcome; 96.2% of the tumors were classified WHO grade I and II and 3.7% were malignant (WHO grade III). Adjuvant treatment was administered in 5.7%; 2.9% had relapse and one patient died (tumor-related mortality = 1.4%). After surgery, 91% of the patients attended regular school/university and/or professional training.

CONCLUSIONS

This study shows that epileptological outcome within this group is promising and stable and oncological outcome has a very good prognosis. However, oncological FU must not be dismissed as a small percentage of patients who suffer from malignant tumors and adjuvant treatment, relapse, and mortality have to be considered.

Epilepsy surgery in the United States: Analysis of data from the National Association of Epilepsy Centers

OBJECTIVE

To examine trends in epilepsy-related surgical procedures performed at major epilepsy centers in the US between 2003 and 2012, and in the service provision infrastructure of epilepsy centers over the same time period.

METHODS

We analyzed data from the National Association of Epilepsy Centers' (NAEC) annual surveys. The total annual figures, annual average figures per center and annual rates of each surgical procedure based on US population numbers for that year were calculated. Additional information on center infrastructure and manpower was also examined.

RESULTS

The number of the NAEC's level 3 and level 4 epilepsy centers submitting annual survey reports increased from 37 centers in 2003 to 189 centers in 2012. The average reported number of Epilepsy Monitoring Unit (EMU) beds per center increased from 7 beds in 2008 to 8 beds in 2012. Overall annual EMU admission rates doubled between 2008 and 2012 but the average number of EMU admissions and epilepsy surgeries performed per center declined over the same period. The annual rate of anterior temporal lobectomies (ATL) for mesial temporal sclerosis (MTS) declined by >65% between 2006 and 2010. The annual rate of extratemporal surgery exceeded that of ATL for MTS from 2008 onwards, doubled between 2007 and 2012 and comprised 38% of all resective surgeries in 2012. Vagus nerve stimulator implant rates consistently increased year on year and exceeded resective surgeries in 2011 and 2012.

CONCLUSION

The last decade has seen a major change in the US epilepsy surgery landscape. Temporal lobectomies, particularly for MTS, have declined despite an increase in EMU admissions. On the other hands, case complexity correspondingly increased as evidenced by more extratemporal surgery, intracranial recordings and palliative procedures.

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.

Is psychiatric assessment essential for better epilepsy surgery outcomes?

Epilepsy surgery is one of the most accepted and beneficial treatment for resistant epilepsies. However there is some variability in the comprehensive epilepsy care programs offered globally. Many centers do not do a psychiatric assessment unless required. It is now evident from a large body of research that epilepsy is associated with psychiatric morbidity which is also seen in patients considered for epilepsy surgery. There is also evidence to state that the risk for worsening or de novo psychiatric disorders is often seen post surgery. This calls for a comprehensive psychiatric assessment of all patients enrolled for the epilepsy surgery program to be evaluated pre and post surgically to minimize the risk of post surgical psychological disturbances and/or poor quality of life. Efficacious treatment of psychiatric disorders in those having psychiatric morbidity contributes to improved patient wellbeing, seizure freedom and better quality of life. Hence there is a need for most centers globally to include regular psychiatric assessment of epilepsy surgery patients as a protocol.

Minimally invasive surgical approaches for temporal lobe epilepsy

Surgery can be a highly effective treatment for medically refractory temporal lobe epilepsy (TLE). The emergence of minimally invasive resective and nonresective treatment options has led to interest in epilepsy surgery among patients and providers. Nevertheless, not all procedures are appropriate for all patients, and it is critical to consider seizure outcomes with each of these approaches, as seizure freedom is the greatest predictor of patient quality of life. Standard anterior temporal lobectomy (ATL) remains the gold standard in the treatment of TLE, with seizure freedom resulting in 60-80% of patients. It is currently the only resective epilepsy surgery supported by randomized controlled trials and offers the best protection against lateral temporal seizure onset. Selective amygdalohippocampectomy techniques preserve the lateral cortex and temporal stem to varying degrees and can result in favorable rates of seizure freedom but the risk of recurrent seizures appears slightly greater than with ATL, and it is not clear whether neuropsychological outcomes are improved with selective approaches. Stereotactic radiosurgery presents an opportunity to avoid surgery altogether, with seizure outcomes now under investigation. Stereotactic laser thermo-ablation allows destruction of the mesial temporal structures with low complication rates and minimal recovery time, and outcomes are also under study. Finally, while neuromodulatory devices such as responsive neurostimulation, vagus nerve stimulation, and deep brain stimulation have a role in the treatment of certain patients, these remain palliative procedures for those who are not candidates for resection or ablation, as complete seizure freedom rates are low. Further development and investigation of both established and novel strategies for the surgical treatment of TLE will be critical moving forward, given the significant burden of this disease.

The piriform, perirhinal, and entorhinal cortex in seizure generation

Understanding neural network behavior is essential to shed light on epileptogenesis and seizure propagation. The interconnectivity and plasticity of mammalian limbic and neocortical brain regions provide the substrate for the hypersynchrony and hyperexcitability associated with seizure activity. Recurrent unprovoked seizures are the hallmark of epilepsy, and limbic epilepsy is the most common type of medically-intractable focal epilepsy in adolescents and adults that necessitates surgical evaluation. In this review, we describe the role and relationships among the piriform (PIRC), perirhinal (PRC), and entorhinal cortex (ERC) in seizure-generation and epilepsy. The inherent function, anatomy, and histological composition of these cortical regions are discussed. In addition, the neurotransmitters, intrinsic and extrinsic connections, and the interaction of these regions are described. Furthermore, we provide evidence based on clinical research and animal models that suggest that these cortical regions may act as key seizure-trigger zones and, even, epileptogenesis.

Proton MR Spectroscopy in Patients with Structural MRI-Negative Temporal Lobe Epilepsy

BACKGROUND AND PURPOSE

With conventional magnetic resonance imaging (MRI), 20-30% of patients with temporal lobe epilepsy (TLE) have negative pathological MRI findings. Further investigations of the role of magnetic resonance spectroscopy (MRS) in the pre-surgical evaluation of patients with MRI-negative TLE are important to avoid intracranial EEG recording and to better understand the mechanism of the epileptogenic process. This study aimed to compare the measurements of N-acetylaspartate (NAA), creatine (Cr), and choline (Cho) in the hippocampi of MRI-negative TLE patients and normal subjects.

METHODS

Twenty patients with MRI-negative TLE and 10 age-matched healthy control subjects underwent MRI and MRS. The concentrations of NAA, Cr, and Cho and the ratios of NAA/Cr and NAA/(Cr+Cho) were measured. Seven of these 20 patients also underwent surgical treatment for TLE. Their pathological results and surgical outcomes were evaluated.

RESULTS

In the hippocampi ipsilateral to the seizure side, the NAA/Cr and NAA/(Cr+Cho) ratios were significantly decreased compared with the ratios of the hippocampi contralateral to the seizure side and the normal control hippocampi. There was no significant difference between the hippocampi contralateral to the seizure side and the normal control hippocampi. The pathological results from the patients who underwent temporal lobe resection indicated mild to moderate gliosis and minimal loss of neurons. Five patients were seizure-free during the follow-up period of 9- 47 months (mean 27.7 months).

CONCLUSIONS

In MRI-negative TLE, significant reductions in the NAA/Cr and NAA/(Cr+Cho) ratios ipsilateral to the seizure side may help lateralize and localize the epileptogenic zone.

Lateralization of mesial temporal lobe epilepsy with chronic ambulatory electrocorticography

OBJECTIVE

Patients with suspected mesial temporal lobe (MTL) epilepsy typically undergo inpatient video-electroencephalography (EEG) monitoring with scalp and/or intracranial electrodes for 1 to 2 weeks to localize and lateralize the seizure focus or foci. Chronic ambulatory electrocorticography (ECoG) in patients with MTL epilepsy may provide additional information about seizure lateralization. This analysis describes data obtained from chronic ambulatory ECoG in patients with suspected bilateral MTL epilepsy in order to assess the time required to determine the seizure lateralization and whether this information could influence treatment decisions.

METHODS

Ambulatory ECoG was reviewed in patients with suspected bilateral MTL epilepsy who were among a larger cohort with intractable epilepsy participating in a randomized controlled trial of responsive neurostimulation. Subjects were implanted with bilateral MTL leads and a cranially implanted neurostimulator programmed to detect abnormal interictal and ictal ECoG activity. ECoG data stored by the neurostimulator were reviewed to determine the lateralization of electrographic seizures and the interval of time until independent bilateral MTL electrographic seizures were recorded.

RESULTS

Eighty-two subjects were implanted with bilateral MTL leads and followed for 4.7 years on average (median 4.9 years). Independent bilateral MTL electrographic seizures were recorded in 84%. The average time to record bilateral electrographic seizures in the ambulatory setting was 41.6 days (median 13 days, range 0-376 days). Sixteen percent had only unilateral electrographic seizures after an average of 4.6 years of recording.

SIGNIFICANCE

About one third of the subjects implanted with bilateral MTL electrodes required >1 month of chronic ambulatory ECoG before the first contralateral MTL electrographic seizure was recorded. Some patients with suspected bilateral MTL seizures had only unilateral electrographic seizures. Chronic ambulatory ECoG in patients with suspected bilateral MTL seizures provides data in a naturalistic setting, may complement data from inpatient video-EEG monitoring, and can contribute to treatment decisions.

Look back to leap forward: The emerging new role of magnetoencephalography (MEG) in nonlesional epilepsy

This review considers accumulating evidence for a new role of MEG/MSI in increasing the diagnostic yield of supposedly negative MRIs, and suggests changes in the use of MEG/MSI in presurgical epilepsy evaluations. Specific alterations in practice protocols for both the MEG practitioner (i.e. physician magnetoencephalographer) and MEG user (i.e. referring physician) are proposed that should further enhance the overall value of MEG/MSI. Although advances in MEG analysis methods will likely become increasingly assisted by computers, interpretive competency and prudent clinical judgment remain irreplaceable.

Impact of psychogenic nonepileptic seizures on epilepsy presurgical investigation and surgical outcomes

INTRODUCTION

We sought to determine the percentage of patients undergoing presurgical assessment that had both psychogenic nonepileptic seizures (PNESs) and epileptic seizures (ESs) captured within our telemetry unit and how this affected progression to surgery and describe eventual outcomes in patients with a history of mixed PNESs/ESs who underwent surgery.

MATERIAL AND METHODS

To determine what happened to patients who had PNESs recorded during a presurgical workup, we reviewed the records of 725 patients admitted to our telemetry unit for presurgical assessment between 2007 and 2013 and identified those with PNESs and ESs recorded. To determine outcomes postsurgery in operated patients who had mixed PNESs/ESs, we also reviewed the records of 519 patients who had had epilepsy surgery between 1999 and 2012 and identified those within this group who also had PNESs prior to surgery.

RESULTS

Nineteen of the 725 patients had PNESs captured during their presurgical telemetry along with ESs captured on either this or a previous study. Four of these patients were ultimately offered surgery. Nine of the 519 patients with a history of PNESs underwent epilepsy surgery. At 1 to 5years of follow-up (mean: 4.1years) of those nine patients, five were still having ESs and three patients had worsening or new-onset PNESs. At the last follow-up, four had had a worthwhile improvement.

DISCUSSION

This study suggests that recent outcomes for people with mixed PNESs/ESs are not as promising as previously described and that PNESs should remain a relative contraindication for surgery.

Epilepsy surgery: current status and ongoing challenges

This article reviews the current status of surgical treatment of epilepsy and introduces the ongoing challenges. Seizure outcome of resective surgery for focal seizures associated with focal lesions is satisfactory. Particularly for mesial temporal lobe epilepsy, surgical treatment should be considered from the earlier stage of the disease. Meanwhile, surgical outcome in nonlesional extratemporal lobe epilepsy is still to be improved using various approaches. Disconnective surgeries reduce surgical complications of extensive resections while achieving equivalent or better seizure outcomes. Multiple subpial transection is still being modified expecting a better outcome by transection to the vertical cortices along the sulci- and multi-directional transection from a single entry point. Hippocampal transection is expected to preserve memory function while interrupting the abnormal epileptic synchronization. Proper selection or combination of subdural and depth electrodes and a wide-band analysis of electroencephalography may improve the accurate localization of epileptogenic region. Patients for whom curative resective surgery is not indicated because of generalized or bilateral multiple nature of their epilepsies, neuromodulation therapies are options of treatment which palliate their seizures.

The brain connectome as a personalized biomarker of seizure outcomes after temporal lobectomy

OBJECTIVE

We examined whether individual neuronal architecture obtained from the brain connectome can be used to estimate the surgical success of anterior temporal lobectomy (ATL) in patients with temporal lobe epilepsy (TLE).

METHODS

We retrospectively studied 35 consecutive patients with TLE who underwent ATL. The structural brain connectome was reconstructed from all patients using presurgical diffusion MRI. Network links in patients were standardized as Z scores based on connectomes reconstructed from healthy controls. The topography of abnormalities in linkwise elements of the connectome was assessed on subnetworks linking ipsilateral temporal with extratemporal regions. Predictive models were constructed based on the individual prevalence of linkwise Z scores >2 and based on presurgical clinical data.

RESULTS

Patients were more likely to achieve postsurgical seizure freedom if they exhibited fewer abnormalities within a subnetwork composed of the ipsilateral hippocampus, amygdala, thalamus, superior frontal region, lateral temporal gyri, insula, orbitofrontal cortex, cingulate, and lateral occipital gyrus. Seizure-free surgical outcome was predicted by neural architecture alone with 90% specificity (83% accuracy), and by neural architecture combined with clinical data with 94% specificity (88% accuracy).

CONCLUSIONS

Individual variations in connectome topography, combined with presurgical clinical data, may be used as biomarkers to better estimate surgical outcomes in patients with TLE.

Automatic segmentation of deep intracerebral electrodes in computed tomography scans

BACKGROUND

Invasive monitoring of brain activity by means of intracerebral electrodes is widely practiced to improve pre-surgical seizure onset zone localization in patients with medically refractory seizures. Stereo-Electroencephalography (SEEG) is mainly used to localize the epileptogenic zone and a precise knowledge of the location of the electrodes is expected to facilitate the recordings interpretation and the planning of resective surgery. However, the localization of intracerebral electrodes on post-implant acquisitions is usually time-consuming (i.e., manual segmentation), it requires advanced 3D visualization tools, and it needs the supervision of trained medical doctors in order to minimize the errors. In this paper we propose an automated segmentation algorithm specifically designed to segment SEEG contacts from a thresholded post-implant Cone-Beam CT volume (0.4 mm, 0.4 mm, 0.8 mm). The algorithm relies on the planned position of target and entry points for each electrode as a first estimation of electrode axis. We implemented the proposed algorithm into DEETO, an open source C++ prototype based on ITK library.

RESULTS

We tested our implementation on a cohort of 28 subjects in total. The experimental analysis, carried out over a subset of 12 subjects (35 multilead electrodes; 200 contacts) manually segmented by experts, show that the algorithm: (i) is faster than manual segmentation (i.e., less than 1s/subject versus a few hours) (ii) is reliable, with an error of 0.5 mm ± 0.06 mm, and (iii) it accurately maps SEEG implants to their anatomical regions improving the interpretability of electrophysiological traces for both clinical and research studies. Moreover, using the 28-subject cohort we show here that the algorithm is also robust (error < 0.005 mm) against deep-brain displacements (< 12 mm) of the implanted electrode shaft from those planned before surgery.

CONCLUSIONS

Our method represents, to the best of our knowledge, the first automatic algorithm for the segmentation of SEEG electrodes. The method can be used to accurately identify the neuroanatomical loci of SEEG electrode contacts by a non-expert in a fast and reliable manner.

Epilepsy: new advances

Epilepsy affects 65 million people worldwide and entails a major burden in seizure-related disability, mortality, comorbidities, stigma, and costs. In the past decade, important advances have been made in the understanding of the pathophysiological mechanisms of the disease and factors affecting its prognosis. These advances have translated into new conceptual and operational definitions of epilepsy in addition to revised criteria and terminology for its diagnosis and classification. Although the number of available antiepileptic drugs has increased substantially during the past 20 years, about a third of patients remain resistant to medical treatment. Despite improved effectiveness of surgical procedures, with more than half of operated patients achieving long-term freedom from seizures, epilepsy surgery is still done in a small subset of drug-resistant patients. The lives of most people with epilepsy continue to be adversely affected by gaps in knowledge, diagnosis, treatment, advocacy, education, legislation, and research. Concerted actions to address these challenges are urgently needed.

Complications of epilepsy surgery in Sweden 1996–2010: a prospective, population-based study

OBJECT

Detailed risk information is essential for presurgical patient counseling and surgical quality assessments in epilepsy surgery. This study was conducted to investigate major and minor complications related to epilepsy surgery in a large, prospective series.

METHODS

The Swedish National Epilepsy Surgery Register provides extensive population-based data on all patients who were surgically treated in Sweden since 1990. The authors have analyzed complication data for therapeutic epilepsy surgery procedures performed between 1996 and 2010. Complications are classified as major (affecting daily life and lasting longer than 3 months) or minor (resolving within 3 months).

RESULTS

A total of 865 therapeutic epilepsy surgery procedures were performed between 1996 and 2010, of which 158 were reoperations. There were no postoperative deaths. Major complications occurred in 26 procedures (3%), and minor complications in 65 (7.5%). In temporal lobe resections (n = 523), there were 15 major (2.9%) and 41 minor complications (7.8%); in extratemporal resections (n = 275) there were 9 major (3.3%) and 22 minor complications (8%); and in nonresective procedures (n = 67) there were 2 major (3%) and 2 minor complications (3%). The risk for any complication increased significantly with age (OR 1.26 per 10-year interval, 95% CI 1.09–1.45). Compared with previously published results from the same register, there is a trend toward lower complication rates, especially in patients older than 50 years.

CONCLUSIONS

This is the largest reported prospective series of complication data in epilepsy surgery. The complication rates comply well with published results from larger single centers, confirming that epilepsy surgery performed in the 6 Swedish centers is safe. Patient age should be taken into account when counseling patients before surgery.

Perceptions of epilepsy surgery: a systematic review and an explanatory model of decision-making

BACKGROUND

Clear evidence supports the benefits of surgery over medical therapy for patients with refractory focal epilepsy. Surgical procedures meet the needs of fewer than 2% of those eligible. Referral to a tertiary epilepsy center early in the course of disease is recommended; however, patients live with disabling and life-threatening seizures for an average of 22years before considering surgical treatment. Reasons for this treatment gap are unclear.

PURPOSE

A critical analysis of the literature addressing perceptions of surgical treatment for epilepsy is placed in the context of a brief history and current treatment guidelines. Common conceptual themes shaping perceptions of epilepsy surgery are identified.

DATA SOURCES

Data sources used for this study were PubMed-MEDLINE and PsycINFO from 2003 to December 2013; hand searches of reference lists.

DATA SYNTHESIS

Nine papers that addressed patient perceptions of surgery for epilepsy and three papers addressing physician attitudes were reviewed. Treatment misperceptions held by both patients and physicians lead to undertreatment and serious health consequences. Fear of surgery, ignorance of treatment options, and tolerance of symptoms emerge as a triad of responses central to weighing treatment risks and benefits and, ultimately, to influencing treatment decision-making. Our novel explanatory framework serves to illustrate and explain relationships among contributory factors.

LIMITATION

Comparisons across studies are limited by the heterogeneity of study populations and by the fact that no instrument has been developed to consistently measure disability in refractory focal epilepsy.

CONCLUSION

Exploring the components of decision-making for the management of refractory focal epilepsy from the patient's perspective presents a new angle on a serious contemporary challenge in epilepsy care and may lead to explanation as to why there is reluctance to embrace a safe and effective treatment.

Sensing-enabled hippocampal deep brain stimulation in idiopathic nonhuman primate epilepsy

Epilepsy is a debilitating condition affecting 1% of the population worldwide. Medications fail to control seizures in at least 30% of patients, and deep brain stimulation (DBS) is a promising alternative treatment. A modified clinical DBS hardware platform was recently described (PC+S) allowing long-term recording of electrical brain activity such that effects of DBS on neural networks can be examined. This study reports the first use of this device to characterize idiopathic epilepsy and assess the effects of stimulation in a nonhuman primate (NHP). Clinical DBS electrodes were implanted in the hippocampus of an epileptic NHP bilaterally, and baseline local field potential (LFP) recordings were collected for seizure characterization with the PC+S. Real-time automatic detection of ictal events was demonstrated and validated by concurrent visual observation of seizure behavior. Seizures consisted of large-amplitude 8- to 25-Hz oscillations originating from the right hemisphere and quickly generalizing, with an average occurrence of 0.71 ± 0.15 seizures/day. Various stimulation parameters resulted in suppression of LFP activity or in seizure induction during stimulation under ketamine anesthesia. Chronic stimulation in the awake animal was studied to evaluate how seizure activity was affected by stimulation configurations that suppressed broadband LFPs in acute experiments. This is the first electrophysiological characterization of epilepsy using a next-generation clinical DBS system that offers the ability to record and analyze neural signals from a chronically implanted stimulating electrode. These results will direct further development of this technology and ultimately provide insight into therapeutic mechanisms of DBS for epilepsy.

Long-term treatment with responsive brain stimulation in adults with refractory partial seizures

OBJECTIVE

The long-term efficacy and safety of responsive direct neurostimulation was assessed in adults with medically refractory partial onset seizures.

METHODS

All participants were treated with a cranially implanted responsive neurostimulator that delivers stimulation to 1 or 2 seizure foci via chronically implanted electrodes when specific electrocorticographic patterns are detected (RNS System). Participants had completed a 2-year primarily open-label safety study (n = 65) or a 2-year randomized blinded controlled safety and efficacy study (n = 191); 230 participants transitioned into an ongoing 7-year study to assess safety and efficacy.

RESULTS

The average participant was 34 (±11.4) years old with epilepsy for 19.6 (±11.4) years. The median preimplant frequency of disabling partial or generalized tonic-clonic seizures was 10.2 seizures a month. The median percent seizure reduction in the randomized blinded controlled trial was 44% at 1 year and 53% at 2 years (p < 0.0001, generalized estimating equation) and ranged from 48% to 66% over postimplant years 3 through 6 in the long-term study. Improvements in quality of life were maintained (p < 0.05). The most common serious device-related adverse events over the mean 5.4 years of follow-up were implant site infection (9.0%) involving soft tissue and neurostimulator explantation (4.7%).

CONCLUSIONS

The RNS System is the first direct brain responsive neurostimulator. Acute and sustained efficacy and safety were demonstrated in adults with medically refractory partial onset seizures arising from 1 or 2 foci over a mean follow-up of 5.4 years. This experience supports the RNS System as a treatment option for refractory partial seizures.

CLASSIFICATION OF EVIDENCE

This study provides Class IV evidence that for adults with medically refractory partial onset seizures, responsive direct cortical stimulation reduces seizures and improves quality of life over a mean follow-up of 5.4 years.

Hemispherectomy for treatment of refractory epilepsy in the pediatric age group: a systematic review

OBJECT

Evidence in support of hemispherectomy stems from a multitude of retrospective studies illustrating individual institutions' experience. A systematic review of this topic, however, is lacking in the literature.

METHODS

A systematic review of hemispherectomy for the treatment of refractory epilepsy available up to October 2013 was performed using the following inclusion criteria: reports of a total of 10 or more patients in the pediatric age group (≤ 20 years) undergoing hemispherectomy, seizure outcome reported after a minimum follow-up of 1 year after the initial procedure, and description of the type of hemispherectomy. Only the most recent paper from institutions that published multiple papers with overlapping study periods was included. Two reviewers independently applied the inclusion criteria and extracted all the data.

RESULTS

Twenty-nine studies with a total of 1161 patients met the inclusion criteria. Seizure outcome was available for 1102 patients, and the overall rate of seizure freedom at the last follow-up was 73.4%. Sixteen studies (55.2%) exclusively reported seizure outcomes of a single type of hemispherectomy. There was no statistically significant difference in seizure outcome and type of hemispherectomy (p = 0.737). Underlying etiology was reported for 85.4% of patients with documented seizure outcome, and the overall distribution of acquired, developmental, and progressive etiologies was 30.5%, 40.7%, and 28.8%, respectively. Acquired and progressive etiologies were associated with significantly higher seizure-free rates than developmental etiologies (p < 0.001). Twenty of the 29 studies (69%) reported complications. The overall rate of hydrocephalus requiring CSF diversion was 14%. Mortality within 30 days was 2.2% and was not statistically different between types of hemispherectomy (p = 0.787).

CONCLUSIONS

Hemispherectomy is highly effective for treating refractory epilepsy in the pediatric age group, particularly for acquired and progressive etiologies. While the type of hemispherectomy does not have any influence on seizure outcome, hemispherotomy procedures are associated with a more favorable complication profile.

Neurologists' knowledge of and attitudes toward epilepsy surgery: a national survey

OBJECTIVES

In the current study, we aim to assess potential neurologist-related barriers to epilepsy surgery among Canadian neurologists.

METHODS

A 29-item, pilot-tested questionnaire was mailed to all neurologists registered to practice in Canada. Survey items included the following: (1) type of medical practice, (2) perceptions of surgical risks and benefits, (3) knowledge of existing practice guidelines, and (4) barriers to surgery for patients with epilepsy. Neurologists who did not complete the questionnaire after the initial mailing were contacted a second time by e-mail, fax, or telephone. After this reminder, the survey was mailed a second time to any remaining nonresponders.

RESULTS

In total, 425 of 796 neurologists returned the questionnaire (response rate 53.5%). Respondents included 327 neurologists who followed patients with epilepsy in their practice. More than half (56.6%) of neurologists required patients to be drug-resistant and to have at least one seizure per year before considering surgery, and nearly half (48.6%) failed to correctly define drug-resistant epilepsy. More than 75% of neurologists identified inadequate health care resources as the greatest barrier to surgery for patients with epilepsy.

CONCLUSIONS

A substantial proportion of Canadian neurologists are unaware of recommended standards of practice for epilepsy surgery. Access also appears to be a significant barrier to epilepsy surgery and surgical evaluation. As a result, we are concerned that patients with epilepsy are receiving inadequate care. A greater emphasis must be placed on knowledge dissemination and ensuring that the infrastructure and personnel are in place to allow patients to have timely access to this evidence-based treatment.

Randomized Trials and Collaborative Research in Epilepsy Surgery: Future Directions

Background:

Although randomized controlled trials (RCTs) are the gold standard for evaluating therapeutic interventions, surgical RCTs are particularly challenging and few have been done in the field of epilepsy surgery. We assess the level of RCT activity in epilepsy surgery and propose feasible alternatives to develop sustainable research initiatives in this area.

Methods:

We undertook a systematic review of the world literature to assess the level of RCT activity in epilepsy surgery. Previous personal experience with RCTs in epilepsy surgery and examples of successful Canadian multicentre research networks were reviewed to propose initiatives for sustainable, valid research in epilepsy surgery.

Results:

We identified 12 RCTs in epilepsy surgery, including 692 patients, of whom 416 were involved in vagus nerve stimulation, 16 in various brain electrostimulation procedures, 180 in comparisons of different surgical techniques, and 80 in a comparison of medical versus surgical therapy. Most studies were of short duration (median = 3 months, range 3-12 months). In the area of resective surgery, only temporal lobe epilepsy has been subjected to any type of RCT comparison. All RCTs have been done within the last 13 years. There were no multicentre Canadian surgical studies.

Conclusion:

The adoption of RCTs in epilepsy surgery has been slow and difficult worldwide. Because of its universal health care system and its well established epilepsy surgery centres, Canada is in a strong position to create a national epilepsy surgery research initiative capable of undertaking high quality, sustainable research in epilepsy surgery.

Outcomes after Epilepsy Surgery

Epilepsy surgery is a highly effective and durable treatment for specific types of drug resistant epilepsy such as temporal lobe epilepsy. assessment of outcomes is essential in epilepsy surgery, which is an irreversible intervention for a chronic condition. Excellent short-term results of resective epilepsy surgery have been established. In the last years more information regarding long term outcomes have been published. This article reviews the best available evidence about the best measures to assess outcomes and the most important evidence. The outcomes reviewed in this article are the following: seizure outcome, social and psychiatric outcomes, complications and mortality.

Advanced [(18)F]FDG and [(11)C]flumazenil PET analysis for individual outcome prediction after temporal lobe epilepsy surgery for hippocampal sclerosis

Purpose

We have previously shown that an imaging marker, increased periventricular [¹¹C]flumazenil ([¹¹C]FMZ) binding, is associated with failure to become seizure free (SF) after surgery for temporal lobe epilepsy (TLE) with hippocampal sclerosis (HS). Here, we investigated whether increased preoperative periventricular white matter (WM) signal can be detected on clinical [¹⁸F]FDG-PET images. We then explored the potential of periventricular FDG WM increases, as well as whole-brain [¹¹C]FMZ and [¹⁸F]FDG images analysed with random forest classifiers, for predicting surgery outcome.

Methods

Sixteen patients with MRI-defined HS had preoperative [¹⁸F]FDG and [¹¹C]FMZ-PET. Fifty controls had [¹⁸F]FDG-PET (30), [¹¹C]FMZ-PET (41), or both (21). Periventricular WM signal was analysed using Statistical Parametric Mapping (SPM8), and whole-brain image classification was performed using random forests implemented in R (http://www.r-project.org). Surgery outcome was predicted at the group and individual levels.

Results

At the group level, non-seizure free (NSF) versus SF patients had periventricular increases with both tracers. Against controls, NSF patients showed more prominent periventricular [¹¹C]FMZ and [¹⁸F]FDG signal increases than SF patients. All differences were more marked for [¹¹C]FMZ. For individuals, periventricular WM signal increases were seen at optimized thresholds in 5/8 NSF patients for both tracers. For SF patients, 1/8 showed periventricular signal increases for [¹¹C]FMZ, and 4/8 for [¹⁸F]FDG. Hence, [¹⁸F]FDG had relatively poor sensitivity and specificity. Random forest classification accurately identified 7/8 SF and 7/8 NSF patients using [¹¹C]FMZ images, but only 4/8 SF and 6/8 NSF patients with [¹⁸F]FDG.

Conclusion

This study extends the association between periventricular WM increases and NSF outcome to clinical [¹⁸F]FDG-PET, but only at the group level. Whole-brain random forest classification increases [¹¹C]FMZ-PET's performance for predicting surgery outcome.

Long-term outcomes in patients after epilepsy surgery failure

PURPOSE

The primary aim of this study was to analyze the long-term outcomes of patients who were classified as Engel IV one year after resective epilepsy surgery. The secondary objectives were to evaluate the effectiveness of different treatment options and to examine the reasons that the patients did not undergo resective reoperation.

METHODS

Our study was designed as a retrospective open-label investigation of the long-term outcomes of 34 patients (12% of all surgically treated patients) who were classified as Engel IV one year after epilepsy surgery.

RESULTS

At the last follow-up visit (average of 7.6 ± 4.2 years after surgery), 12 of the 34 examined patients (35.3%) were still classified as Engel IV; 22 of the 34 patients (64.7%) were improved (Engel I-III). Of the 34 patients, 8 (23.5%) achieved an excellent outcome, classified as Engel I, 3 patients (8.8%) were classified as Engel II, and 11 patients (32.4%) as Engel III. The seizure outcome in the patients classified as Engel I was achieved by resective reoperation in 4; by a change in antiepileptic medication in 3 patients; and by vagus nerve stimulation (VNS) in 1 patient. The seizure outcome of Engel II was achieved by a change in antiepileptic medication in all 3 patients. Of the 34 patients, a total of 6 (17.6%) underwent resective reoperation only. The major reasons for this were the absence of a plausible hypothesis for invasive re-evaluation, the risk of postoperative deficit, and multifocal epilepsy in the rest of patients.

CONCLUSION

Although the reoperation rate was relatively low in our series, we can achieve better or even excellent seizure outcomes using other procedures in patients for whom resective surgery initially failed.

Weighing the value of memory loss in the surgical evaluation of left temporal lobe epilepsy: a decision analysis

OBJECTIVES

Anterior temporal lobectomy is curative for many patients with disabling medically refractory temporal lobe epilepsy, but carries an inherent risk of disabling verbal memory loss. Although accurate prediction of iatrogenic memory loss is becoming increasingly possible, it remains unclear how much weight such predictions should have in surgical decision making. Here we aim to create a framework that facilitates a systematic and integrated assessment of the relative risks and benefits of surgery versus medical management for patients with left temporal lobe epilepsy.

METHODS

We constructed a Markov decision model to evaluate the probabilistic outcomes and associated health utilities associated with choosing to undergo a left anterior temporal lobectomy versus continuing with medical management for patients with medically refractory left temporal lobe epilepsy. Three base-cases were considered, representing a spectrum of surgical candidates encountered in practice, with varying degrees of epilepsy-related disability and potential for decreased quality of life in response to post-surgical verbal memory deficits.

RESULTS

For patients with moderately severe seizures and moderate risk of verbal memory loss, medical management was the preferred decision, with increased quality-adjusted life expectancy. However, the preferred choice was sensitive to clinically meaningful changes in several parameters, including quality of life impact of verbal memory decline, quality of life with seizures, mortality rate with medical management, probability of remission following surgery, and probability of remission with medical management.

SIGNIFICANCE

Our decision model suggests that for patients with left temporal lobe epilepsy, quantitative assessment of risk and benefit should guide recommendation of therapy. In particular, risk for and potential impact of verbal memory decline should be carefully weighed against the degree of disability conferred by continued seizures on a patient-by-patient basis.

Transsylvian selective amygdalohippocampectomy for treatment of medial temporal lobe epilepsy: Surgical technique and operative nuances to avoid complications

Background:

A number of different surgical techniques are effective for treatment of drug-resistant medial temporal lobe epilepsy. Of these, transsylvian selective amygdalohippocampectomy (SA), which was originally developed to maximize temporal lobe preservation, is arguably the most technically demanding to perform. Recent studies have suggested that SA may result in better neuropsychological outcomes with similar postoperative seizure control as standard anterior temporal lobectomy, which involves removal of the lateral temporal neocortex.

Methods:

In this article, the authors describe technical nuances to improve the safety of SA.

Results:

Wide sylvian fissure opening and use of neuronavigation allows an adequate exposure of the amygdala and hippocampus through a corticotomy within the inferior insular sulcus. Avoidance of rigid retractors and careful manipulation and mobilization of middle cerebral vessels will minimize ischemic complications. Identification of important landmarks during amygdalohippocampectomy, such as the medial edge of the tentorium and the third nerve within the intact arachnoid membranes covering the brainstem, further avoids operator disorientation.

Conclusion:

SA is a safe technique for resection of medial temporal lobe epileptogenic foci leading to drug-resistant medial temporal lobe epilepsy.

Comparison of brain perfusion SPECT parameters accuracy for seizure localization in extratemporal lobe epilepsy with discordant pre-surgical data

OBJECTIVE

Extratemporal lobe epilepsy is difficult to localize. We aimed to define the best parameter(s) of SPECT for confirmation of seizure origin among the region of maximum cerebral perfusion in ictal phase (MP), maximum change of cerebral perfusion from interictal to ictal phase (MC), and maximum extent of hyperperfusion in ictal phase (ME) of (99m)Tc ECD brain perfusion SPECT as well as combined SPECT parameters, and combined SPECT and MRI for seizure localization in extratemporal lobe epilepsy.

MATERIALS AND METHODS

Twenty intractable extratemporal lobe epilepsy patients who had (99m)Tc-ECD brain SPECT were reviewed. Sensitivity, specificity, positive predictive value, negative predictive value and accuracy of single SPECT parameter, combined SPECT parameters, and combined SPECT and MRI parameters for localization of seizure origin were calculated using pathology and surgical outcomes (Engel class I and II) as gold standards.

RESULTS

Combined SPECT parameters provided more specificity, PPV and accuracy than single SPECT parameters. The best combined SPECT parameters was MP+MC with 80.6 % accuracy, 92.4 % specificity and 43.8 % PPV. Combination of SPECT parameter with MRI (ME+MRI) was the most sensitive (41.7 %), specific (97.5 %), accurate (88.2 %) parameter and had highest PPV (76.9 %) and NPV (89.3 %) for seizure localization. It improved specificity and PPV when compared to MRI alone.

CONCLUSION

Combined SPECT parameters improved the specificity and accuracy in seizure localization. The most specific and accurate SPECT combination is MP+MC. The combined SPECT parameter with MRI further improved sensitivity, specificity, accuracy, PPV and NPV. The authors recommend using SPECT combination, MP+MC, when MRI is negative and ME+MRI when there is MRI lesion.

The significance of parahippocampal high gamma activity for memory preservation in surgical treatment of atypical temporal lobe epilepsy

OBJECTIVE

Resective surgery for mesial temporal lobe epilepsy (MTLE) with a correspondent lesion has been established as an effective and safe procedure. Surgery for temporal lobe epilepsies with bilateral hippocampal sclerosis or without correspondent lesions, however, carries a higher risk of devastating memory decline, underscoring the importance of establishing the memory-dominant side preoperatively and adopting the most appropriate procedure. In this study, we focused on high gamma activities (HGAs) in the parahippocampal gyri and investigated the relationship between memory-related HGAs and memory outcomes after hippocampal transection (HT), a hippocampal counterpart to neocortical multiple subpial transection. The transient nature of memory worsening after HT provided us with a rare opportunity to compare HGAs and clinical outcomes without risking permanent memory disorders.

METHODS

We recorded electrocorticography from parahippocampal gyri of 18 patients with temporal lobe epilepsy while they executed picture naming and recognition tasks. Memory-related HGA was quantified by calculating differences in power amplification of electrocorticography signals in a high gamma range (60-120 Hz) between the two tasks. We compared memory-related HGAs from correctly recognized and rejected trials (hit-HGA and reject-HGA). Using hit-HGA, we determined HGA-dominant sides and compared them with memory outcomes after HT performed on seven patients.

RESULTS

We observed memory-related HGA mainly between 500 and 600 msec poststimulus. Hit-HGA was significantly higher than reject-HGA. Three patients who had surgery on the HGA-dominant side experienced transient memory worsening postoperatively. The postoperative memory functions of the other four patients remained unchanged.

SIGNIFICANCE

Parahippocampal HGA was indicated to reflect different memory processes and be compatible with the outcomes of HT, suggesting that HGA could provide predictive information on whether the mesial temporal lobe can be resected without causing memory worsening. This preliminary study suggests a refined surgical strategy for atypical MTLE based on reliable memory lateralization.

Feasibility of using an online tool to assess appropriateness for an epilepsy surgery evaluation

OBJECTIVES

To examine the applicability of applying an online tool to determine the appropriateness of referral for an epilepsy surgical evaluation and to determine whether appropriateness scores are concordant with the clinical judgment of epilepsy specialists.

METHODS

We prospectively applied the tool in 107 consecutive patients with focal epilepsy seen in an epilepsy outpatient clinic. Variables collected included seizure type, epilepsy duration, seizure frequency, seizure severity, number of antiepileptic drugs (AEDs) tried, AED-related side effects, and the results of investigations. Appropriateness ratings were then compared with retrospectively collected information concerning whether a surgical evaluation had been considered.

RESULTS

Thirty-nine patients (36.4%) were rated as appropriate for an epilepsy surgical evaluation, all of whom had adequately tried 2 or more appropriate AEDs. The majority of patients (84.6%) rated as appropriate had previously been considered or referred for an epilepsy surgical evaluation. Tool feasibility of use was high, with the exception of assessing whether previous AED trials had been adequate and discrepancies between physician and patient reports of AED side effects.

CONCLUSIONS

Our evidence-based, online clinical decision tool is easily applied and able to determine whether patients with focal epilepsy are appropriate for a surgical evaluation. Future validation of this tool will require application in clinical practice and assessment of potential improvements in patient outcomes.