Seizure outcome after anterior temporal lobectomy and its predictors in patients with apparent temporal lobe epilepsy and normal MRI

Prevalence of nonlesional focal epilepsy in an adult epilepsy clinic

PURPOSE

To evaluate the prevalence of nonlesional focal epilepsy in an adult epilepsy clinic and its refractoriness to antiepileptic drug therapy.

BACKGROUND

Focal epilepsy is frequently, but not always, associated with structural epileptogenic lesions identifiable on magnetic resonance imaging (MRI).

METHODS

We analyzed the data from all patients evaluated at an adult epilepsy clinic from January 2002 to December 2011. Clinical and paraclinical findings were used to diagnose focal epilepsy. Magnetic resonance imaging were reviewed and classified as normal, with an epileptogenic lesion, or with a lesion of unclear epileptogenicity. Epileptogenic lesions were further categorized as tumours, vascular malformations, gliosis (including hippocampal atrophy/sclerosis), and malformations of cortical development. Our study group included patients with no lesions on MRI. Pharmacoresistance of patients with nonlesional focal epilepsy was assessed using the ILAE and Perucca's criterias.

RESULTS

Out of 1521 patients evaluated (mean age 44 years; range 14-93 years), 843 had focal epilepsy. Magnetic resonance imaging data, available for 806 (96%) subjects, showed epileptogenic lesions in 65%, no obvious epileptogenic lesions in 31% and lesions of unclear epileptogenicity in 4%. Magnetic resonance imaging-identified lesions included gliosis due to an acquired insult (52% including 17% of hippocampal atrophy or sclerosis), tumours (29%), vascular malformations (16%) and malformations of cortical development (10%). Fifty-two percent of nonlesional focal epileptic patients were drug-refractory.

CONCLUSION

In a tertiary epilepsy clinic, close to a third of patients with focal epilepsy were found to be nonlesional, half of which were drug-resistant.

Tailored Temporal Lobectomy for Medically Intractable Epilepsy

BACKGROUND:

There have been only a few large series that have used a tailored temporal lobectomy.

OBJECTIVE:

To clarify whether tailoring a temporal lobe resection will lead to equivalent epilepsy outcomes or have the same predictive factors for success when compared with standard resections.

METHODS:

Retrospective analysis of 222 patients undergoing a tailored temporal lobe resection. Demographic measures and typical factors influencing outcome were evaluated.

RESULTS:

Pathology included 222 cases. With a mean follow-up of 5.4 years, 70% of patients achieved Engel class I outcome. A significant factor predicting Engel class I outcome on multivariate analysis was lesional pathology (P = .04). Among patients with hippocampal sclerosis, extent of lateral neocortical resection and hippocampal resection were not statistically associated with Engel class I outcome (P = .93 and P = .24). However, an analysis of Engel class subgroups a to d showed that patients who had a complete hippocampectomy in the total series were more likely to achieve an Engel class Ia outcome (P = .04). This was also true among patients with hippocampal sclerosis (P = .03). Secondarily, generalized seizure (P = .01) predicted outcome less than Engel class I. Predictive of poor outcome was the need for preoperative electrodes (P = .02). Complications included superior quadrant visual field defects, 2 cases of permanent dysphasia, and 3 wound infections.

CONCLUSION:

Predictors of successful seizure outcome for a tailored temporal lobectomy are similar to standard lobectomy. Patients with secondarily generalized epilepsy and cases in which preoperative subdural electrodes were thought necessary were less likely to achieve class I outcome. Among Engel class I cases, those who had a complete hippocampectomy were more likely to achieve Engel class Ia outcome.

Neuroimaging in epilepsy in tropics

Epilepsy is a major public health problem in many tropical countries. Also, some of the tropical diseases are major contributors to the higher prevalence of epilepsy in these countries. The etiologic factors responsible for epilepsy in these countries are quite different from those in the developed world. This article discusses the etiologic factors and neuroimaging of epilepsy in light of the conditions in these tropical countries.

Coexistence of idiopathic generalized epilepsy among surgically treated patients with drug-resistant temporal lobe epilepsy

INTRODUCTION

Failure to identify the association antiepileptic drug (AED)-resistant temporal lobe epilepsy (TLE) with idiopathic generalized epilepsy (IGE) can interfere with decision for anterior temporal lobectomy (ATL) and prediction of post-ATL seizure outcome.

METHODS

Out of the 664 consecutive patients who underwent ATL between March 1995 and December 2007, 12 (1.8%) had coexisting IGE. The decision for ATL was made after a thorough discussion in the multidisciplinary patient management conference based upon the concordance between the clinical, electroencephalographic and magnetic resonance imaging data. All of them underwent epilepsy surgery for AED-resistant TLE.

RESULTS

In seven of the 12 patients, IGE was not identified until post-ATL. During a median follow-up period of 8.5 years, 8 of our 12 patients were seizure-free; the remaining 4 patients only had infrequent myoclonus. In two them, AEDs were discontinued; others were on montherapy for IGE.

CONCLUSIONS

Our study highlights the rare association of IGE with TLE, the most common AED-resistant focal epilepsy syndrome. As the seizure outcome following ATL is similar in AED-resistant TLE patients with and without IGE, their co-existence is not a contraindication for ATL. Future studies should explore the molecular genetic basis of the rare association between these two epilepsy syndromes.

The value of intraoperative electrocorticography in surgical decision making for temporal lobe epilepsy with normal MRI

PURPOSE

We hypothesized that acute intraoperative electrocorticography (ECoG) might identify a subset of patients with magnetic resonance imaging (MRI)-negative temporal lobe epilepsy (TLE) who could proceed directly to standard anteromesial resection (SAMR), obviating the need for chronic electrode implantation to guide resection.

METHODS

Patients with TLE and a normal MRI who underwent acute ECoG prior to chronic electrode recording of ictal onsets were evaluated. Intraoperative interictal spikes were classified as mesial (M), lateral (L), or mesial/lateral (ML). Results of the acute ECoG were correlated with the ictal-onset zone following chronic ECoG. Onsets were also classified as "M,""L," or "ML." Positron emission tomography (PET), scalp-EEG (electroencephalography), and Wada were evaluated as adjuncts.

KEY FINDINGS

Sixteen patients fit criteria for inclusion. Outcomes were Engel class I in nine patients, Engel II in two, Engel III in four, and Engel IV in one. Mean postoperative follow-up was 45.2 months. Scalp EEG and PET correlated with ictal onsets in 69% and 64% of patients, respectively. Wada correlated with onsets in 47% of patients. Acute intraoperative ECoG correlated with seizure onsets on chronic ECoG in all 16 patients. All eight patients with "M" pattern ECoG underwent SAMR, and six (75%) experienced Engel class I outcomes. Three of eight patients with "L" or "ML" onsets (38%) had Engel class I outcomes.

SIGNIFICANCE

Intraoperative ECoG may be useful in identifying a subset of patients with MRI-negative TLE who will benefit from SAMR without chronic implantation of electrodes. These patients have uniquely mesial interictal spikes and can go on to have improved postoperative seizure-free outcomes.

Is it necessary to define the ictal onset zone with EEG prior to performing resective epilepsy surgery?

When evaluating candidates for neurosurgical treatment for medically intractable epilepsy, is it always necessary to define the region of seizure onset with EEG? A simple answer to this question is not possible. There are specific situations where surgery is commonly performed without clear EEG ictal localization, and other situations where electrical localization is mandatory. However, opinions differ in many other situations. What are the core issues for determining when EEG localization is necessary? Neuroimaging is imperfect. It does not always accurately identify the site of seizure origination, because seizures do not always arise from visible structural lesions. EEG localization is also imperfect, as well as expensive and time consuming. Sometimes the site of origin is not identified, or a region of spread is misidentified as site of origin. False localization and lateralization can occur. Finally, epilepsy surgery is imperfect. It can produce life-changing results, but it carries risk, and surgical failure is not rare. The limitations of these methods, and the high stakes of epilepsy surgery imply that we should be very cautious to omit EEG studies. The desire to improve access to epilepsy surgery, and to minimize the expense and risk from inpatient EEG studies, must be weighed against the possibility of an ineffective resection. To improve outcomes, improvements in both neuroimaging and EEG techniques are needed.

Epilepsy surgery: recommendations for India

The following article recommends guidelines for epilepsy surgery for India. This article reviews the indications, the various surgical options available and the outcome of surgery for drug resistant epilepsy based on current evidence. Epilepsy surgery is a well-established option for patients who have been diagnosed to have drug resistant epilepsy (DRE) (on at least two appropriate, adequate anti-epileptic drugs (AEDs) (either in monotherapy or in combination) with continuing seizures), where the presurgical work-up has shown concordance of structural imaging (magnetic resonance imaging) and electrical mapping data (electroencephalography (EEG), video EEG). There may be a requirement of functional imaging techniques in a certain number of DRE like positron emission tomography (PET), single photon emission tomography, (SPECT)). Invasive monitoring should be restricted to a few when all noninvasive investigations are inconclusive, there is a dual pathology or there is a discordance of noninvasive data. The types of surgery could be curative (resective surgeries: amygdalo hippocampectomy, lesionectomy and multilobar resections; functional surgeries: hemispherotomy) and palliative (multiple subpial transaction, corpus callosotomy, vagal nerve stimulation). Epilepsy surgery in indicated cases has a success range from 50 to 86% in achieving seizure freedom as compared with <5% success rate with AEDs only in persons with DRE. Centers performing surgery should be categorized into Level I and Level II.

Long-term epilepsy surgery outcomes in patients with MRI-negative temporal lobe epilepsy

PURPOSE

The outcome of surgery in patients with temporal lobe epilepsy (TLE) and normal high-resolution magnetic resonance imaging (MRI) has been significantly worse than in patients with unilateral hippocampal damage upon MRI. The purpose of this study was to determine the long-term outcomes of consecutive true MRI-negative TLE patients who all underwent standardized preoperative evaluation with intracranial electroencephalography (EEG) electrodes.

METHODS

In this study we present all adult MRI-negative TLE surgery candidates evaluated between January 1990 and December 2006 at Kuopio Epilepsy Center in Kuopio University Hospital, which provides a national center for epilepsy surgery in Finland. During this period altogether 146 TLE surgery candidates were evaluated with intracranial electrodes, of whom 64 patients with normal high-resolution MRI were included in this study.

RESULTS

Among the 38 patients who finally underwent surgery, at the latest follow-up (mean 5.8 years), 15 (40%) were free of disabling seizures (Engel class I) and 6 (16%) were seizure-free (Engel class IA). Twenty-one (55%) of 38 patients had poor outcomes (Engel class III-IV). Outcomes did not change compared to 12-month follow-up. Histopathologic examination failed to reveal any focal pathology in 68% of our MR-negative cases. Only patients with noncongruent positron emission tomography (PET) results had worse outcomes (p = 0.044).

DISCUSSION

Our results suggest that epilepsy surgery outcomes in MRI-negative TLE patients are comparable with extratemporal epilepsy surgery in general. Seizure outcomes in the long-term also remain stable. Modern imaging techniques could further improve the postsurgical seizure-free rate. However, these patients usually require chronic intracranial EEG evaluation to define epileptogenic areas.

MRI-negative temporal lobe epilepsy: is there a role for PET?

MRI-negative PET-positive Temporal Lobe Epilepsy: A Distinct Surgically Remediable Syndrome

Carne RP, O'Brien TJ, Kilpatrick CJ, MacGregor LR, Hicks RJ, Murphy MA, Bowden SC, Kaye AH, Cook MJ

Brain 2004;127:2276–2285

Most patients with nonlesional temporal lobe epilepsy (NLTLE) will have the findings of hippocampal sclerosis (HS) on a high-resolution MRI. However, a significant minority of patients with NLTLE and electroclinically well-lateralized temporal lobe seizures have no evidence of HS on MRI. Many of these patients have concordant hypometabolism on fluorodeoxyglucose-PET ([18F]FDG-PET). The pathophysiologic basis of this latter group remains uncertain. We aimed to determine whether NLTLE without HS on MRI represents a variant of or a different clinicopathologic syndrome from that of NLTLE with HS on MRI. The clinical, EEG, [18F]FDG-PET, histopathologic, and surgical outcomes of 30 consecutive NLTLE patients with well-lateralized EEG but without HS on MRI (HS–ve TLE) were compared with 30 consecutive age- and sex-matched NLTLE patients with well-lateralized EEG with HS on MRI (HS+ve TLE). Both the HS+ve TLE group and the HS–ve TLE patients had a high degree of [18F]FDG-PET concordant lateralization (26 of 30 HS–ve TLE vs. 27 of 27 HS+ve TLE). HS–ve TLE patients had more widespread hypometabolism on [18F]FDG-PET by blinded visual analysis [odds ratio (OR,+∞(2.51,–); P = 0.001]. The HS–ve TLE group less frequently had a history of febrile convulsions [OR,0.077 (0.002 to 0.512), P = 0.002], more commonly had a delta rhythm at ictal onset [OR,3.67 (0.97 to 20.47); P = 0.057], and less frequently had histopathologic evidence of HS [OR,0 (0 to 0.85); P = 0.031]. No significant difference in surgical outcome despite half of those without HS having a hippocampal-sparing procedure. Based on the findings outlined, HS–ve PET-positive TLE may be a surgically remediable syndrome distinct from HS+ve TLE, with a pathophysiologic basis that primarily involves lateral temporal neocortical rather than mesial temporal structures.

Outcome after cortico-amygdalo-hippocampectomy in patients with temporal lobe epilepsy and normal MRI

RATIONALE

We describe seizure and neuropsychological outcome obtained after CAH in patients with TLE and normal MRI evaluated in the modern imaging era.

METHODS

Forty-five adult consecutive patients with TLE and normal MRI were studied. All patients had neuropsychological testing, interictal and ictal EEG recordings and MRI. They were divided into two groups: Group 1 (n=18), included patients in whom non-invasive neurophysiological evaluation was lateralizing and Group 2 (n=27) included patients with non-lateralizing neurophysiological data who were submitted to invasive recordings.

RESULTS

Seventy-seven percent of the Group 1 patients were rated as Engel I; 11% were rated as Engel II and 11% as Engel III. In Group 2, there were 57% of patients seizure-free, 26% in Engel II and 14% in Engel III. Pre-operatively, mean general IQ was 82 and 78 in Groups 1 and 2, respectively; post-operatively, mean general IQ was respectively 86 and 71. Some degree of verbal memory decline was noted in all patients submitted to dominant temporal lobe resection in both Groups 1 and 2. At last follow-up visit, 22% of Group 1 and 11% of Group 2 patients were receiving no antiepileptic drugs (AED).

CONCLUSIONS

Our data showed that patients with TLE and normal MRI could get good surgical results after CAH although 60% of them would need invasive recordings and their results regarding seizure control and cognition were worse than those obtained in patients with MRI defined temporal lobe lesions. Caution should be taken in offering dominant temporal lobe resection to this subset of patients.

Epilepsy surgery outcomes in temporal lobe epilepsy with a normal MRI

PURPOSE

To determine the long-term efficacy of anterior temporal lobectomy for medically refractory temporal lobe epilepsy in patients with nonlesional magnetic resonance imaging (MRI).

METHODS

We identified a retrospective cohort of 44 patients with a nonlesional modern "seizure protocol" MRI who underwent anterior temporal lobectomy for treatment of medically refractory partial epilepsy. Postoperative seizure freedom was determined by Kaplan-Meyer survival analysis. Noninvasive preoperative diagnostic factors potentially associated with excellent surgical outcome were examined by univariate analysis in the 40 patients with follow-up of >1 year.

RESULTS

Engel class I outcomes (free of disabling seizures) were observed in 60% (24 of 40) patients. Preoperative factors associated with Engel class I outcome were: (1) absence of contralateral or extratemporal interictal epileptiform discharges, (2) subtraction ictal single photon emission computed tomography (SPECT) Coregistered to MRI (SISCOM) abnormality localized to the resection site, and (3) subtle nonspecific MRI findings in the mesial temporal lobe concordant to the resection.

DISCUSSION

In carefully selected patients with temporal lobe epilepsy and a nonlesional MRI, anterior temporal lobectomy can often render patients free of disabling seizures. This favorable rate of surgical success is likely due to the detection of concordant abnormalities that indicate unilateral temporal lobe epilepsy in patients with nonlesional MRI.

Enhanced activity during associative encoding in the affected hippocampus in right temporal lobe epilepsy patients

Mnestic deficits represent the core cognitive impairment of patients with temporal lobe epilepsy (TLE), irrespective of the existence of overt morphological lesions. Compared to controls, patients with symptomatic TLE show altered functional activation patterns in fMRI studies on memory processes. But, so far, such studies have rarely investigated patients with temporal lobe epilepsy of unknown cause. Therefore, in the current study, a small sample of 6 right TLE patients with normal structural MRIs was compared to controls with respect to brain activity during encoding of face-name associations using fMRI. Compared to controls, patients retrieved fewer face-name associations correctly, but showed significantly greater activation of the affected hippocampus for successfully encoded stimuli. Therefore, higher hippocampal activation seems necessary for successful encoding of associations in patients compared to controls. But, this process is not entirely successful since the patients cannot achieve the same performance as controls. In conclusion, the hyperactivation of the hippocampus might represent a compensational but inefficient process.

Long-term outcome after temporal lobe epilepsy surgery in 434 consecutive adult patients

Object

The aim of this study was to evaluate the long-term efficacy of temporal lobe epilepsy (TLE) surgery and potential risk factors for seizure recurrence after surgery.

Methods

This retrospective study included 434 consecutive adult patients who underwent TLE surgery at Bethel Epilepsy Centre between 1991 and 2002.

Results

Hippocampal sclerosis was found in 62% of patients, gliosis in 17.3%, tumors in 20%, and focal cortical dysplasia (FCD) in 6.9%. Based on a Kaplan-Meier analysis, the probability of Engel Class I outcome for the patients overall was 76.2% (95% CI 71–81%) at 6 months, 72.3% (95% CI 68–76%) at 2 years, 71.1% (95% CI 67–75%) at 5 years, 70.8% (95% CI 65–75%) at 10 years, and 69.4% (95% CI 64–74%) at 16 years postoperatively. The likelihood of remaining seizure free after 2 years of freedom from seizures was 90% (95% CI 82–98%) for 16 years. Seizure relapse occurred in all subgroups. Patients with FCD had the highest risk of recurrence (hazard ratio 2.15, 95% CI 0.849–5.545). Predictors of remission were the presence of hippocampal atrophy on preoperative MR imaging and a family history of epilepsy. Predictors of relapse were the presence of bilateral interictal sharp waves and versive seizures. Six-month follow-up electroencephalography predicted relapse in patients with FCD. Short epilepsy duration was predictive of seizure remission in patients with tumors and gliosis; 28.1% of patients were able to discontinue antiepileptic medications without an increased risk of seizure recurrence (hazard ratio 1.05, 95% CI 0.933–1.20).

Conclusions

These findings highlight the role of etiology in prediction of long-term outcome after TLE surgery.

Ictal EEG remains the prominent predictor of seizure-free outcome after temporal lobectomy in epileptic patients with normal brain MRI

PURPOSE

While an abnormal pre-operative high-resolution brain MRI portends a favorable outcome in patients undergoing resective epilepsy surgery for medically intractable localization-related epilepsy (LRE), a normal MRI is less favorable. Ascertaining desirable pre-operative predictors for successful anterior temporal lobectomy (ATL) in LRE patients with a normal brain MRI is essential to better anticipate surgical outcome.

METHODS

Patients with LRE and normal temporal structures on MRI underwent ATL at two epilepsy centers in the southeastern US (FL and NC). Outcome was separated into those patients that were seizure free (SF), and those that were not seizure free (NSF), and those NSF were stratified in accordance with the Engel classification system. Those with a pre-operative history of clinical risk factors, unilateral anterior temporal interictal epileptiform discharges (IEDs), well localized scalp ictal EEG with rhythmic temporal theta at onset, localized PET/ictal SPECT, and Wada asymmetry with >2.5/8, were evaluated for the purpose of predicting outcome. Where appropriate, data is presented as a median (mean +/- S.D.).

RESULTS

Thirty-nine patients, median age 33 years, were followed up 2 years (3+/-1.2) after ATL. Overall, 22/39 (56.4%) patients were identified as SF, and 17/39 (43.6%) patients were NSF. Ictal EEG with rhythmic temporal theta at onset was the only predictive measure of seizure-free outcome (p=0.001, Fisher's exact test), and also favorably correlated with seizure reduction (p=0.0001, r(2)=0.34, multiple regression analysis). None of the other predictors examined added greater predictive value.

CONCLUSIONS

ATL is a favorable option for patients with LRE even when high-resolution brain MRI reveals normal temporal structures. Normal brain MRI patients with localizing pre-operative scalp ictal EEG, have better outcomes following ATL.

Impaired facial emotion recognition in patients with mesial temporal lobe epilepsy associated with hippocampal sclerosis (MTLE-HS): Side and age at onset matters

To define the determinants of impaired facial emotion recognition (FER) in patients with mesial temporal lobe epilepsy associated with hippocampal sclerosis (MTLE-HS), we examined 76 patients with unilateral MTLE-HS, 36 prior to antero-mesial temporal lobectomy (AMTL) and 40 after AMTL, and 28 healthy control subjects with a FER test consisting of 60 items (20 each for anger, fear, and happiness). Mean percentages of the accurate responses were calculated for different subgroups: right vs. left MTLE-HS, early (age at onset <6 years) vs. late-onset, and before vs. after AMTL. After controlling for years of education, duration of epilepsy and number of antiepileptic drugs (AEDs) taken, on multivariate analysis, fear recognition was profoundly impaired in early-onset right MTLE-HS patients compared to other MTLE patients and control subjects. Happiness recognition was significantly better in post-AMTL MTLE-HS patients compared to pre-AMTL patients while anger and fear recognition did not differ. We conclude that patients with right MTLE-HS with age at seizure onset <6 years are maximally predisposed to impaired fear recognition. In them, right AMTL does not further worsen FER abilities. Longitudinal studies comparing FER in the same patients before and after AMTL will be required to refine and confirm our cross-sectional observations.

Epilepsy surgery in patients with normal or nonfocal MRI scans: integrative strategies offer long-term seizure relief

PURPOSE

Excisional surgery achieves seizure freedom in a large proportion of children with intractable lesional epilepsy, but the outcome for children without a focal lesion on MRI is less clear. We report the outcome of a cohort predominantly of children with nonlesional intractable partial epilepsy undergoing resective surgery.

METHODS

We studied 102 patients with nonlesional intractable partial epilepsy who underwent excisional surgery. The epileptogenic region was identified by integrating clinical exam and video-EEG data complemented by ictal SPECT (n = 40), PET (n = 10), extraoperative subdural monitoring (n = 80), and electrocorticography (n = 22). All patients had follow-up greater than 2 years, 76 patients had 5-year follow-up, and 43 patients had 10-year follow-up.

RESULTS

A total of 66 resections were unilobar; 36 were multilobar. One patient died of causes unrelated to seizures or surgery. At 2-year follow-up, 44 of 101 patients were seizure-free, 15 experienced >90% reduction, 17 had >50% reduction, and 25 were unchanged. At 5-year follow-up, 35 of 76 patients were seizure-free, 12 experienced >90% reduction, 12 had >50% reduction, and 17 were unchanged. At 10-year follow-up, 16 of 43 patients were seizure-free, 13 experienced >90% reduction, 7 had >50% reduction, and 7 were unchanged. Outcomes correlated with the presence of convergent focal interictal spikes (p < 0.005) on the scalp EEG and completeness of resection (p < 0.0005).

CONCLUSIONS

Our findings demonstrate that excisional surgery is successful in the majority of children with nonlesional partial epilepsy. A multimodal integrative approach can minimize the size of resection and alleviate the need for invasive EEG monitoring. Focal interictal spikes and completeness of resection predict good outcome. The benefits of surgery are long-lasting.

Intractable pediatric temporal lobe epilepsy in the United States: examination of race, age, sex, and insurance status as factors predicting receipt of resective treatment

OBJECT

For patients with intractable temporal lobe epilepsy (ITLE), resection of the temporal lobe has been proven to be far superior to continued medical management. The goal of this study was to evaluate on a national level whether race and other sociodemographic factors are predictors of receipt of resective treatment for pediatric ITLE.

METHODS

A retrospective cohort study was performed using the Kids' Inpatient Database covering the period of 1997 through 2003. Only children admitted for resection for ITLE (ICD-9-CM 345.41, 345.51; primary procedure code 01.53) were included. Variables studied included patient race, age, sex, and primary payer.

RESULTS

Multivariate analyses revealed no significant difference in the odds of undergoing resection for ITLE for black children compared with nonblack children (odds ratio [OR] 0.66, 95% confidence interval [CI] 0.28-1.53, p = 0.327), or between female and male children (OR 1.11, 95% CI 0.76-1.63, p = 0.586). Older children were more likely to undergo resection for ITLE (OR 1.07, 95% CI 1.03-1.11, p < 0.001 per 1 year increase in age), as were children with private insurance (OR 2.21, 95% CI 1.34-3.63, p = 0.002).

CONCLUSIONS

In this first nationwide analysis of pediatric ITLE, older age and private insurance status independently predicted which children were more likely to receive surgical treatment for ITLE on a national level, whereas sex did not. Black children with ITLE were no less likely to receive surgical intervention than nonblack children. Future nationwide analyses will be required to determine whether these trends for pediatric ITLE surgery remain stable over time.

Magnetic resonance spectroscopy in animal models of epilepsy

The noninvasive localization of the epileptogenic zone continues to be a challenge in many patients that present as candidates for possible epilepsy surgery. Magnetic resonance imaging (MRI) techniques provide accurate anatomical definition, but despite their high resolution, these techniques fail to visualize the pathological neocortical and hippocampal changes in a sizable number of patients with focal pathologies. Further, visualized lesions on MRI may not all produce seizures. One of the keys to the understanding of the epileptogenic zone lies in the recognition of the metabolic alterations that occur in the setting of epileptic seizures. Magnetic resonance spectroscopy (MRS) is a valuable tool that can be used to study the metabolic changes seen in both acute and chronic animal models of epilepsy. Such study allows for the identification of epileptic tissue with high sensitivity and specificity. We present here a review of the use of MRS in animal models of epilepsy.

The contribution of 18F-FDG PET in preoperative epilepsy surgery evaluation for patients with temporal lobe epilepsy

OBJECTIVE

To assess the predictive diagnostic added value of positron emission tomography (PET) in preoperative epilepsy surgery evaluation for patients with temporal lobe epilepsy (TLE).

METHODS

A meta-analysis of publications from 1992 to 2006 was performed. Forty-six studies were identified that met inclusion criteria presenting detailed diagnostic test results and a classified postoperative outcome. Studies exclusively reporting on patients with brain tumors or on children were excluded.

RESULTS

The analyses were complicated by significant differences in study design and often by lack of precise patient data. Ipsilateral PET hypometabolism showed a predictive value of 86% for good outcome. The predictive value was 80% in patients with normal MRI and 72% in patients with non-localized ictal scalp EEG. In a selected population of 153 TLE patients with a follow-up of >12 months PET correlated well with other non-invasive diagnostic tests, but none of the odds ratios of any test combination was significant.

CONCLUSION

Our data confirm that ipsilateral PET hypometabolism may be an indicator for good postoperative outcome in presurgical evaluation of drug-resistant TLE, although the actual diagnostic added value remained questionable and unclear. PET does not appear to add value in patients localized by ictal scalp EEG and MRI. Prospective studies limited to non-localized ictal scalp EEG or MRI-negative patients are required for validation.

Dissociation of short- and long-term face memory: Evidence from long-term recency effects in temporal lobe epilepsy

We tested whether memory deficits in temporal lobe epilepsy (TLE) are better described by a single- or dual-store memory model. To this aim, we analyzed the influence of TLE and proactive interference (PI) on immediate and 24-h long-term recency effects during face recognition in 16 healthy participants and 18 right and 21 left non-surgical TLE patients. PI in healthy participants or TLE erased the long-term recency effect, but left the immediate recency effect unaffected. Although the immediate recency effect was still visible in right TLE patients, the number of detected recency items during immediate recognition was decreased in right TLE compared to left TLE. Right TLE was also related to decreased detection of pre-recency items during delayed recognition compared to left TLE, and decreased detection of pre-recency items during immediate recognition under PI. The results show that the temporal lobes are necessary for the long-term recency effect, but not for the immediate recency effect, and thus speak for a dissociation of short- and long-term memory for faces. Right TLE is related to more severe long-term memory deficits than left TLE and is also related to additional short-term memory deficits for faces.

Corpora amylacea in mesial temporal lobe epilepsy: Clinico-pathological correlations

PURPOSE

To investigate the electro-clinical significance of premature accumulation of corpora amylacea (CoA) in the resected hippocampus of patients with medically refractory mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS).

METHODS

We compared the clinical and EEG characteristics, and post-operative seizure outcome of 373 (mean age 29.4 years, range 7-55 years) surgically treated MTLE-HS patients with (MTLE-HS-CoA(+), n=129 [34.5%]) and without (MTLE-HS-CoA(-), n=244 [65.5%]) CoA.

RESULTS

Age at surgery was significantly higher and duration of epilepsy before surgery was significantly longer for MTLE-HS-CoA(+) patients compared to MTLE-HS-CoA(-) patients. Although the distribution of interictal epileptiform EEG abnormalities did not differ, type 1 ictal EEG pattern was more frequent in MTLE-HS-CoA(+) patients. Among the 21 patients with major interictal psychosis detected prior to epilepsy surgery, 19 (90.5%) belonged to MTLE-HS-CoA(+) group. Schizophrenia-like psychosis was most prevalent. The post-operative seizure-free outcome was comparable, but significantly more MTLE-HS-CoA(-) patients were free of antiepileptic drugs.

CONCLUSIONS

Overall, our observations support the hypothesis that the pathological process in MTLE-HS is progressive. MTLE-HS-CoA(+) patients are predisposed to increased psychiatric morbidity. In vivo detection of hippocampal CoA accumulation in the future will help us to understand the neurobiological significance of this phenomenon.

Persistent seizures following left temporal lobe surgery are associated with posterior and bilateral structural and functional brain abnormalities

PURPOSE

To perform a quantitative MRI and retrospective electrophysiological study to investigate whether persistent post-surgical seizures may be due to brain structural and functional abnormalities in temporal lobe cortex beyond the margins of resection and/or bilateral abnormalities in patients with temporal lobe epilepsy (TLE).

METHODS

In 22 patients with left TLE and histopathological evidence of hippocampal sclerosis, we compared pre-surgical brain morphology between patients surgically remedied (Engel's I) and patients with persistent post-surgical seizures (PPS, Engel's II-IV) using voxel-based morphometry (VBM). Routine pre-surgical EEG and invasive and non-invasive telemetry investigations were additionally compared between patient groups.

RESULTS

Results indicated widespread structural and functional abnormalities in patients with PPS relative to surgically remedied patients. In particular, patients with PPS had significantly reduced volume of the ipsilateral posterior medial temporal lobe and contralateral medial temporal lobe relative to surgically remedied patients. Furthermore, successful surgery was associated with clear anterior (89%) and unilateral (100%) temporal lobe EEG abnormalities, whilst PPS were associated with widespread ipsilateral (91%) and bilateral (82%) temporal lobe abnormalities.

DISCUSSION

We suggest that these preliminary data support the hypothesis that PPS after temporal lobe surgery are due to functionally connected epileptogenic cortex remaining in the ipsilateral posterior temporal lobe and/or in temporal lobe contralateral to resection.

Face memory in MRI-positive and MRI-negative temporal lobe epilepsy

PURPOSE

Effects of MRI-positive (MRI(+)) as compared to MRI-negative (MRI(-)) temporal lobe epilepsy (TLE) on face memory are not yet known.

METHODS

We studied 24 MRI(-) (11 right/13 left) and 20 MRI(+) (13 right/7 left) TLE patients, 12 generalized epilepsy patients, and 12 healthy subjects undergoing diagnostic workup with 24-72-h Video-EEG-monitoring. Twenty faces were shown, and had to be recognized from 40 faces immediately and after a 24-h delay.

RESULTS

MRI(+) and MRI(-) right TLE (RTLE) patients showed deficits in face recognition compared to controls or generalized epilepsy, consistent with right temporal lobe dominance for face recognition. MRI(+) RTLE patients had deficits in both immediate and delayed recognition, while MRI(-) RTLE patients showed delayed recognition deficits only. The RTLE groups showed comparable delayed recognition deficits. Separate analyses in which the MRI(+) group included patients with hippocampal sclerosis only, did not alter results. Furthermore, MRI(-) RTLE had a worse delayed recognition than MRI(-) left TLE (LTLE). On the other hand, MRI(+) RTLE did not differ from MRI(+) LTLE in delayed recognition. Combining MRI(-) and MRI(+) TLE groups, we found differences between RTLE and LTLE in delayed, but not immediate face recognition.

CONCLUSIONS

Our results suggest that a delayed recognition condition might be superior to immediate recognition tests in detecting face memory deficits in MRI(-) RTLE patients. This might explain why former studies in preoperative patients did not observe an immediate face recognition dominance of the right temporal lobe when combining MRI(-) and MRI(+) TLE patients. Our data further point to an important role of the right mesial temporal region in face recognition in TLE.

Sex differences in face recognition memory in patients with temporal lobe epilepsy, patients with generalized epilepsy, and healthy controls

The influence of sex on face recognition memory was studied in 49 patients with temporal lobe epilepsy, 20 patients with generalized epilepsy, and 32 healthy controls. After learning 20 faces, serially presented for 5 seconds each, subjects had to recognize the 20 among 40 faces (including 20 new faces) immediately and 24 hours later. Women had better face recognition than men, with no significant differences between groups. Women's advantage was due mainly to superior delayed recognition. Taken together, the results suggest that sex has a similar impact on face recognition in patients with epilepsy and healthy controls, and that testing delayed face recognition raises sensitivity for sex differences. The influence of sex on face recognition in patients with epilepsy should be acknowledged when evaluating individuals or comparing groups.

Facial Emotion Recognition after Curative Nondominant Temporal Lobectomy in Patients with Mesial Temporal Sclerosis

PURPOSE

The right (nondominant) amygdala is crucial for processing facial emotion recognition (FER). Patients with temporal lobe epilepsy (TLE) associated with mesial temporal sclerosis (MTS) often incur right amygdalar damage, resulting in impaired FER if TLE onset occurred before age 6 years. Consequently, early right mesiotemporal insult has been hypothesized to impair plasticity, resulting in FER deficits, whereas damage after age 5 years results in no deficit. The authors performed this study to test this hypothesis in a uniformly seizure-free postsurgical population.

METHODS

Controls (n=10), early-onset patients (n=7), and late-onset patients (n=5) were recruited. All patients had nondominant anteromedial temporal lobectomy (AMTL), Wada-confirmed left-hemisphere language dominance and memory support, MTS on both preoperative MRI and biopsy, and were Engel class I 5 years postoperatively. By using a standardized (Ekman and Friesen) human face series, subjects were asked to match the affect of one of two faces to that of a simultaneously presented target face. Target faces expressed fear, anger, or happiness.

RESULTS

Statistical analysis revealed that the early-onset group had significantly impaired FER (measured by percentage of faces correct) for fear (p=0.036), whereas the FER of the late-onset group for fear was comparable to that of controls. FER for anger and happiness was comparable across all three groups.

CONCLUSIONS

Despite seizure control/freedom after AMTL, early TLE onset continues to impair FER for frightened expressions (but not for angry or happy expression), whereas late TLE onset does not impair FER, with no indication that AMTL resulted in FER impairment. These results indicate that proper development of the right amygdala is necessary for optimal fear recognition, with other neural processes unable to compensate for early amygdalar damage.

Treatment options and paradigms in childhood temporal lobe epilepsy

Temporal lobe epilepsy in adults is a relatively homogenous syndrome with hippocampal sclerosis being its most common pathologic substrate. In the pediatric age group, low-grade neoplasms and cortical dysplasia are much more common than hippocampal sclerosis. Pediatric temporal lobe epilepsy has distinct semiologic, electrophysiologic and imaging characteristics as compared with its adult counterpart. The various treatment options for pediatric temporal lobe epilepsy include antiepileptic drugs, resective surgery, vagal nerve stimulation and the ketogenic diet. In spite of the multiple antiepileptic drugs currently available, 5-10% of all newly diagnosed cases will remain intractable to medical therapy and should be referred for presurgical evaluation. Resective surgery offers the best chance of seizure freedom in carefully selected patients. Future areas of research include new drug development, better imaging and localization techniques, and brain stimulation.

Epilepsy increases vulnerability of long-term face recognition to proactive interference

Proactive interference (PI) decreases short- and long-term memory in healthy subjects. Neurological patients exhibit a heightened PI effect on short-term memory. It is, however, not known if PI affects long-term memory in neurological patients. We analyzed whether epilepsy heightens the negative effect of PI on long-term face memory. PI was induced by a list of 20 faces learned 24 hours prior to a target list of 20 faces. We tested immediate and 24-hour recognition for both lists. Twelve healthy controls and 42 patients with generalized epilepsy or temporal lobe epilepsy (TLE) were studied. PI led to a decrease in 24-hour recognition in patients with generalized epilepsy and TLE but not in controls. Thus, PI may cause long-term memory disturbances in epilepsy patients. PI was also associated with decreased short-term memory, but only in right TLE. This confirms the dominant role of the right temporal lobe in short-term face memory.

Surgical outcome and predictive factors in adult patients with intractable epilepsy and focal cortical dysplasia

OBJECTIVES

To determine the surgical outcome and prognostic factors in adult patients with intractable epilepsy and focal cortical dysplasia (FCD).

MATERIALS AND METHODS

We retrospectively studied the operative outcome in 21 consecutive adult patients with FCD who underwent surgical treatment for intractable partial epilepsy.

RESULTS

The mean age at surgery was 32.7 years (range, 18-58 years). The median post-operative follow-up was 2.5 years. The FCD was extratemporal in 11 patients, involved the temporal lobe in 10 patients, and was multilobar in eight patients. Eleven patients (52%) were rendered seizure-free, four patients (19%) had >95% reduction in seizures, and two patients (10%) had an 80-94% reduction in seizures. A seizure-free outcome was associated with shorter duration of epilepsy (P = 0.02).

CONCLUSION

Adult patients with FCD may be candidates for surgical treatment of intractable partial epilepsy. Most individuals have neocortical, extrahippocampal seizures and approximately 50% of patients are rendered seizure-free.