Early surgical treatment for epilepsy

Structural Brain Network Abnormalities and the Probability of Seizure Recurrence After Epilepsy Surgery

OBJECTIVE

We assessed preoperative structural brain networks and clinical characteristics of patients with drug-resistant temporal lobe epilepsy (TLE) to identify correlates of postsurgical seizure recurrences.

METHODS

We examined data from 51 patients with TLE who underwent anterior temporal lobe resection (ATLR) and 29 healthy controls. For each patient, using the preoperative structural, diffusion, and postoperative structural MRI, we generated 2 networks: presurgery network and surgically spared network. Standardizing these networks with respect to controls, we determined the number of abnormal nodes before surgery and expected to be spared by surgery. We incorporated these 2 abnormality measures and 13 commonly acquired clinical data from each patient into a robust machine learning framework to estimate patient-specific chances of seizures persisting after surgery.

RESULTS

Patients with more abnormal nodes had a lower chance of complete seizure freedom at 1 year and, even if seizure-free at 1 year, were more likely to relapse within 5 years. The number of abnormal nodes was greater and their locations more widespread in the surgically spared networks of patients with poor outcome than in patients with good outcome. We achieved an area under the curve of 0.84 ± 0.06 and specificity of 0.89 ± 0.09 in predicting unsuccessful seizure outcomes (International League Against Epilepsy [ILAE] 3-5) as opposed to complete seizure freedom (ILAE 1) at 1 year. Moreover, the model-predicted likelihood of seizure relapse was significantly correlated with the grade of surgical outcome at year 1 and associated with relapses up to 5 years after surgery.

CONCLUSION

Node abnormality offers a personalized, noninvasive marker that can be combined with clinical data to better estimate the chances of seizure freedom at 1 year and subsequent relapse up to 5 years after ATLR.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that node abnormality predicts postsurgical seizure recurrence.

Similarities and differences in neuroplasticity mechanisms between brain gliomas and nonlesional epilepsy

OBJECTIVE

To analyze the conceptual and practical implications of a hodotopic approach in neurosurgery, and to compare the similarities and the differences in neuroplasticity mechanisms between low-grade gliomas and nonlesional epilepsy.

METHODS

We review the recent data about the hodotopic organization of the brain connectome, alongside the organization of epileptic networks, and analyze how these two structures interact, suggesting therapeutic prospects. Then we focus on the mechanisms of neuroplasticity involved in glioma natural course and after glioma surgery. Comparing these mechanisms with those in action in an epileptic brain highlights their differences, but more importantly, gives an original perspective to the consequences of surgery on an epileptic brain and what could be expected after pathologic white matter removal.

RESULTS

The organization of the brain connectome and the neuroplasticity is the same in all humans, but different pathologic mechanisms are involved, and specific therapeutic approaches have been developed in epilepsy and glioma surgery. We demonstrate that the "connectome" point of view can enrich epilepsy care. We also underscore how theoretical and practical tools commonly used in epilepsy investigations, such as invasive electroencephalography, can be of great help in awake surgery in general.

SIGNIFICANCE

Putting together advances in understanding of connectomics and neuroplasticity, leads to significant conceptual improvements in epilepsy surgery.

Magnetic resonance imaging connectivity for the prediction of seizure outcome in temporal lobe epilepsy

OBJECTIVE

Currently, approximately 60-70% of patients with unilateral temporal lobe epilepsy (TLE) remain seizure-free 3 years after surgery. The goal of this work was to develop a presurgical connectivity-based biomarker to identify those patients who will have an unfavorable seizure outcome 1-year postsurgery.

METHODS

Resting-state functional and diffusion-weighted 3T magnetic resonance imaging (MRI) was acquired from 22 unilateral (15 right, 7 left) patients with TLE and 35 healthy controls. A seizure propagation network was identified including ipsilateral (to seizure focus) and contralateral hippocampus, thalamus, and insula, with bilateral midcingulate and precuneus. Between each pair of regions, functional connectivity based on correlations of low frequency functional MRI signals, and structural connectivity based on streamline density of diffusion MRI data were computed and transformed to metrics related to healthy controls of the same age.

RESULTS

A consistent connectivity pattern representing the network expected in patients with seizure-free outcome was identified using eight patients who were seizure-free at 1-year postsurgery. The hypothesis that increased similarity to the model would be associated with better seizure outcome was tested in 14 other patients (Engel class IA, seizure-free: n = 5; Engel class IB-II, favorable: n = 4; Engel class III-IV, unfavorable: n = 5) using two similarity metrics: Pearson correlation and Euclidean distance. The seizure-free connectivity model successfully separated all the patients with unfavorable outcome from the seizure-free and favorable outcome patients (p = 0.0005, two-tailed Fisher's exact test) through the combination of the two similarity metrics with 100% accuracy. No other clinical and demographic predictors were successful in this regard.

SIGNIFICANCE

This work introduces a methodologic framework to assess individual patients, and demonstrates the ability to use network connectivity as a potential clinical tool for epilepsy surgery outcome prediction after more comprehensive validation.

Bridging the Gap between Evidence and Practice for Adults with Medically Refractory Temporal Lobe Epilepsy: Is a Change in Funding Policy Needed to Stimulate a Shift in Practice?

Objective. Surgery for medically refractory epilepsy (MRE) in adults has been shown to be effective but underutilized. Comprehensive health economic evaluations of surgery compared with continued medical management are limited. Policy changes may be necessary to influence practice shift. Methods. A critical review of the literature on health economic analyses for adults with MRE was conducted. The MEDLINE, EMBASE, CENTRAL, CRD, and EconLit databases were searched using relevant subject headings and keywords pertaining to adults, epilepsy, and health economic evaluations. The screening was conducted independently and in duplicate. Results. Four studies were identified (1 Canadian, 2 American, and 1 French). Two were cost-utility analyses and 2 were cost-effectiveness evaluations. Only one was conducted after the effectiveness of surgery was established through a randomized trial. All suggested surgery to be favorable in the medium to long term (7-8 years and beyond). The reduction of medication use was the major cost-saving parameter in favor of surgery. Conclusions. Although updated evaluations that are more generalizable across settings are necessary, surgery appears to be a favorable option from a health economic perspective. Given the limited success of knowledge translation endeavours, funder-level policy changes such as quality-based purchasing may be necessary to induce a shift in practice.

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.

Shorter epilepsy duration is associated with better seizure outcome in temporal lobe epilepsy surgery

Objective To investigate the influence of patient’s age and seizure onset on surgical outcome of temporal lobe epilepsy (TLE). Method A retrospective observational investigation performed from a cohort of patients from 2000 to 2012. Results A total of 229 patients were included. One-hundred and eleven of 179 patients (62%) were classified as Engel I in the group with < 50 years old, whereas 33 of 50 (66%) in the group with ≥ 50 years old group (p = 0.82). From those Engel I, 88 (61%) reported epilepsy duration inferior to 10 years and 56 (39%) superior to 10 years (p < 0.01). From the total of patients not seizure free, 36 (42%) reported epilepsy duration inferior to 10 years and 49 (58%) superior to 10 years (p < 0.01). Conclusion Patients with shorter duration of epilepsy before surgery had better postoperative seizure control than patients with longer duration of seizures.

Factors predicting the outcome following medical treatment of mesial temporal epilepsy with hippocampal sclerosis

PURPOSE

There is a lack of information from South America regarding factors that predict the clinical outcomes of patients treated medically for mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS). This study was conducted to determine which of these factors are the most important.

METHODS

This study included 110 South American patients with MTLE-HS treated with antiepileptic drugs. The factors considered included age, gender, age of epilepsy onset, interval between the lesion and the first seizure, central nervous system infection, traumatic brain injury, perinatal asphyxia, febrile convulsion, history of status epilepticus, types of seizures, site of hippocampal sclerosis (HS), extrahippocampal pathology, and electroencephalogram (EEG) abnormalities. The patients were divided into two groups based on the response to treatment: Group I, seizure free for at least two years; and Group II, not seizure free.

RESULTS

On the multivariate analysis, the factors associated with a poor prognosis in terms of seizure frequency and control following treatment included the presence of an early onset of seizure, more than 10 seizures per month before treatment, and EEG abnormalities.

CONCLUSION

The recognition of risk factors, such as early onset of seizures, more than 10 seizures per month before treatment, and EEG abnormalities, could lead to the identification of risk groups among patients with MTLE-HS and refractory epilepsy, possibly designating these individuals as candidates for early epilepsy surgery.

Non-pharmacological treatment options for refractory epilepsy: an overview of human treatment modalities and their potential utility in dogs

Refractory epilepsy is a common disorder both in humans and dogs and treatment protocols are difficult to optimise. In humans, different non-pharmacological treatment modalities currently available include surgery, the ketogenic diet and neurostimulation. Surgery leads to freedom from seizures in 50-75% of patients, but requires strict patient selection. The ketogenic diet is indicated in severe childhood epilepsies, but efficacy is limited and long-term compliance can be problematic. In the past decade, various types of neurostimulation have emerged as promising treatment modalities for humans with refractory epilepsy. Currently, none of these treatment options are used in routine daily clinical practice to treat dogs with the condition. Since many dogs with poorly controlled seizures do not survive, the search for alternative treatment options for canine refractory epilepsy should be prioritised. This review provides an overview of non-pharmacological treatment options for human refractory epilepsy. The current knowledge and limitations of these treatments in canine refractory epilepsy is also discussed.

Implantable stimulator for epileptic seizure suppression with loading impedance adaptability

The implantable stimulator for epileptic seizure suppression with loading impedance adaptability was proposed in this work. The stimulator consisted of the high voltage generator, output driver, adaptor, and switches, can constantly provide the required 40-μA stimulus currents, as the loading impedance varied within 10 kΩ -300 kΩ. The performances of this design have been successfully verified in silicon chip fabricated by a 0.35- μm 3.3-V/24-V CMOS process. The power consumption of this work was only 1.1 mW-1.4 mW. The animal test results with the fabricated chip of proposed design have successfully verified in the Long-Evans rats with epileptic seizures.

Developmental outcomes of childhood-onset temporal lobe epilepsy: a community-based study

PURPOSE

To assess the impact of childhood-onset temporal lobe epilepsy (TLE) on the attainment of normative developmental tasks and identify predictors of long-term developmental outcomes.

METHODS

In 1992-1993, a prospective longitudinal cohort study of childhood-onset TLE was commenced in the State of Victoria, Australia. At review in 2004-2006, we assessed developmental tasks, which are age-specific individual psychosocial achievements tied to particular phases of the lifespan. The cohort comprised 54 individuals (33 female) with a mean age of 20 years (range 12-29), and mean age at TLE onset of 6 years (range 0.2-15).

KEY FINDINGS

Individuals were clustered into three groups representing distinct developmental trajectories: (1) a Normal group (52%) who achieved most of their developmental tasks, (2) an Altered group (37%) who achieved some, and (3) a Delayed group (11%) who achieved few. The groups showed significant cognitive differences, with the Normal group outperforming the Altered and Delayed groups on a range of measures (p < 0.05). Multiple discriminant function analysis indicated that membership of the groups was independently predicted by the chronicity of seizures, cognitive functioning, having surgically remediable epilepsy, and gender (p < 0.001). Seizure chronicity and cognition discriminated between all three trajectories, while surgical intervention and gender primarily discriminated between the Altered and Delayed trajectories.

SIGNIFICANCE

Childhood-onset TLE can disrupt achievement of normative developmental tasks that is independently predicted by medical, biologic, and cognitive factors. Assessment of developmental tasks across the lifespan provides a practical framework for guiding prognostic counseling of patients and families.

Epilepsy surgery utilization: who, when, where, and why?

PURPOSE OF REVIEW

Using the most recent evidence, we provide an update on epilepsy surgery, focusing on its effectiveness, reasons for underutilization, considerations of candidacy and timing for referral for epilepsy surgery evaluation.

RECENT FINDINGS

The course of illness of epilepsy is being characterized. Well conducted studies describe the patterns of seizure remission and relapse with medical therapy and also in response to epilepsy surgery. Epilepsy surgery is highly effective in selected patients with drug-resistant epilepsy (DRE). The risk-benefit of epilepsy surgery is well known and consistent around the world. However, epilepsy surgery remains underutilized. A randomized controlled trial and Clinical Practice Guidelines (CPGs) supporting epilepsy surgery have had no discernible impact on referral rates for epilepsy surgery evaluation. Criteria and guidelines are being developed for identifying patients who need to be referred for epilepsy surgery evaluation. Quality indicators for epilepsy care now also include the need to consider surgical candidacy every 3 years in DRE. New developments in imaging and neurophysiology promise to help clinicians identify and treat patients more accurately.

SUMMARY

Surgery is effective but underused. Comprehensive interventions to translate evidence to practice in epilepsy surgery are urgently needed.

Current challenges in the practice of epilepsy surgery

The accurate prediction of individual outcomes after epilepsy surgery represents a key challenge facing clinicians. It requires a precise understanding of surgical candidacy and the optimal timing of surgery to maximize a range of outcomes, including medical, psychosocial, cognitive, and psychiatric outcomes. We promote careful consideration of how epilepsy has affected an individual's developmental trajectory as key to constructing more differentiated profiles of postsurgical risk or resilience across multiple outcome measures. This life span approach conceives surgery as a crucial "turning point" in an individual's development from which varied outcome trajectories may follow. This helps clinicians understand the expectations patients and families bring to surgery, and emphasizes the interplay of factors that determine a patient's outcome. It also promotes comprehensive, longitudinal assessment of outcome using data analytical techniques that capture individual differences and identify subgroups with similar trajectories. An ongoing challenge facing clinicians is the development of an outcome classification system that incorporates outcomes other than seizures. We illustrate two emerging areas of research shaping how we define surgical candidacy and predict outcome: (1) using cortico-cortical evoked potentials to identify pathways of seizure propagation and cortico-cortical networks mediating cortical functions, and (2) predicting postoperative depression using a model that incorporates psychosocial and neurobiological factors. The latter research points to the importance of routine follow-up and postoperative psychosocial rehabilitation, particularly in patients deemed at "high risk" for poor outcomes so that early treatment interventions can be implemented. Significantly more research is needed to characterize those patients with poor outcomes who may require re-surgery.

Referral pattern for epilepsy surgery after evidence-based recommendations: a retrospective study

BACKGROUND

Class I evidence for surgical effectiveness in refractory temporal lobe epilepsy (TLE) in 2001 led to an American Academy of Neurology practice parameter in 2003 recommending "referral to a surgical epilepsy center on failing appropriate trials of first-line antiepileptic drugs." We examined whether this led to a change in referral patterns to our epilepsy center.

METHODS

We compared referral data for patients with TLE at our center for 1995 to 1998 (group 1, n = 83) and 2005 to 2008 (group 2, n = 102) to determine whether these recommendations resulted in a change in referral patterns for surgical evaluation. Patients with brain tumors, previous epilepsy surgery evaluations, or brain surgery (including epilepsy surgery) were excluded.

RESULTS

We did not find a difference between the groups in the duration from the diagnosis of habitual seizures to referral (17.1 +/- 10.0 vs 18.6 +/- 12.6 years, p = 0.39) or the age at the time of evaluation (34.1 +/- 10.3 vs 37.0 +/- 11.8 years, p = 0.08). However, there was a difference in the distributions of age at evaluation (p = 0.03) and the duration of pharmacotherapy (p = 0.03) between the groups, with a greater proportion of patients in group 2 with drug-resistant epilepsy both earlier and later in their treatment course. Nonepileptic seizures were referred significantly earlier than TLE in either group or when combined.

CONCLUSIONS

Our analysis does not identify a significantly earlier referral for epilepsy surgery evaluation as recommended in the practice parameter, but suggests a hopeful trend in this direction.

Predictors of Unfavourable Seizure Outcome in Patients with Epilepsy in Nepal

Background:

Despite optimal medical therapy, a sizeable number of patients continue to have persistent seizures. We evaluated the association of pretreatment and treatment variables with unfavorable seizure outcome.

Methods:

Patients with follow-up over 12 years in the Nepal Epilepsy Association were evaluated. Patients having seizures for at least a year and already on polytherapy after failure of two monotherapy trials were considered having unfavourable outcome. Variables under study were: age, sex, duration and frequency of seizures prior to treatment, type of seizure, neurological status, Computed Tomography (CT) finding, and failure of first anti-epileptic drug (AED). Bivariate analysis was done with Chi-square and Fisher exact tests. Potential interaction between variables was studied with a logistic regression analysis.

Results:

Out of a total 529 consecutive patients, 490 were included in the study. Unfavorable seizure outcome was seen in 26.8% of patients. Among 284 patients who remained viable for analysis, bivariate analysis showed significant association of unfavorable outcome with frequency of seizure (p 0.01), abnormal neurological status (p 0.01) and failure of first AED (p 0.00), while no significant association was seen with age at onset (p 0.45), sex (p 0.47), duration of seizure (p 0.43), type of seizure (p 0.12), and presence of CT abnormality (p 0.46). The fitted regression model portended an unfavorable prognosis with failure of first AED and abnormal neurological status, however, failed to show significant association with frequency of seizure.

Conclusions:

Failure of first AED trial and associated neurological deficits are significant predictors of unfavorable seizure outcome.

The effect of preoperative body mass index on outcome after temporal lobe epilepsy surgery

PURPOSE

The increasing prevalence of obesity is a significant health care concern. Individuals with obesity, i.e., a body mass index (BMI)>or=30, may have significant comorbid conditions that may increase the risk of general anesthesia and operative procedures. The rationale for the present investigation is to evaluate the importance of obesity on operative outcome in patients with intractable temporal lobe epilepsy undergoing surgical treatment.

METHODS

This study involved a retrospective analysis of 244 adult patients who underwent epilepsy surgery at Mayo Clinic in Rochester, Minnesota between 1990 and 1996. The mean age of patients at surgery was 35 years (range, 18-68 years). There were 108 male patients (44%). Seventy-three patients (30%) were overweight (BMI 26-29), 56 patients (23%) were obese (BMI 30-39), and nine patients (4%) had extreme obesity (BMI>or=40) at the time of surgery.

RESULTS

The BMI was not predictive of the duration of intensive care unit or hospital stay following surgery, perioperative morbidity, or long-term seizure control following epilepsy surgery. Fifteen deaths occurred in the study period remote from the surgical procedure. The mortality during follow-up was increased for patients with extreme obese (p<0.007).

CONCLUSIONS

The perioperative morbidity and seizure outcome following epilepsy surgery was independent of the patient's body weight. However, long-term mortality was significantly increased in the individuals with extreme obesity. The effect of morbid obesity on long-term quality of life after epilepsy surgery may need to be considered in selecting operative candidates.

Longitudinal and cross-sectional analysis of atrophy in pharmacoresistant temporal lobe epilepsy

BACKGROUND

Whether recurrent epileptic seizures induce brain damage is debated. Disease progression in epilepsy has been evaluated only in a few community-based studies involving patients with seizures well controlled by medication. These studies concluded that epilepsy does not inevitably lead to global cerebral damage.

OBJECTIVE

To track the progression of neocortical atrophy in pharmacoresistant temporal lobe epilepsy (TLE) using longitudinal and cross-sectional designs.

METHODS

Using a fully automated measure of cortical thickness on MRI, we studied a homogeneous sample of patients with pharmacoresistant TLE. In the longitudinal analysis (n = 18), fixed-effect models were used to quantify cortical atrophy over a mean interscan interval of 2.5 years (range = 7 to 90 months). In the cross-sectional analysis (n = 121), we correlated epilepsy duration and thickness. To dissociate normal aging from pathologic progression, we compared aging effects in TLE to healthy controls.

RESULTS

The longitudinal analysis mapped progression in ipsilateral temporopolar and central and contralateral orbitofrontal, insular, and angular regions. In patients with more than 14 years of disease, atrophy progressed more rapidly in frontocentral and parietal regions that in those with shorter duration. The cross-sectional study showed progressive atrophy in the mesial and superolateral frontal, and parietal cortices.

CONCLUSIONS

Our combined cross-sectional and longitudinal analysis in patients with pharmacoresistant temporal lobe epilepsy demonstrated progressive neocortical atrophy over a mean interval of 2.5 years that is distinct from normal aging, likely representing seizure-induced damage. The cumulative character of atrophy underlies the importance of early surgical treatment in this group of patients.