ApoE epsilon4 allele and disease duration affect verbal learning in mild temporal lobe epilepsy

Sex and APOE genotype modulate neuropsychological profile and depression in temporal lobe epilepsy

Introduction

Temporal lobe epilepsy is the most common form of focal epilepsy, often associated with cognitive impairments, particularly in memory functions, and depression. Sex and APOE ε4 genotype play a crucial role in modulating cognitive outcomes and depression in various neurological conditions like Alzheimer's disease. However, the combined effects of APOE genotype and sex on cognitive performance and depression in temporal lobe epilepsy have not been previously investigated.

Objective

This study aims to (i) identify impaired cognitive performance and clinically relevant depression; (ii) explore the interaction between sex and APOE ε4 genotype on cognitive performance and depression in individuals with temporal lobe epilepsy.

Methods

We used a comprehensive battery of neuropsychological tests to assess domains such as learning and memory, attention, executive functions, language, and visuo-spatial constructional skills and the Hamilton Depression Rating Scale. We also performed APOE genotyping to assess its role in the study. The final sample was composed by fifty-four patients (53.7% female). Cognitive performance and depression were analyzed using normative cut-off scores. To examine the main effects and interactions of sex and APOE ε4 carrier status on neuropsychological test scores and the Hamilton Depression Rating Scale, we also conducted a two-way Analysis of Variance (ANOVA).

Results

Female APOE ε4 carriers compared to normative cut-offs, exhibited poor performance on multiple test scores, including the MMSE, The Rey Auditory Verbal Learning Test (immediate and delayed recall), The Corsi Block-Tapping Task, The Verbal Fluency Test, The Raven's Standard Progressive Matrices and The Pentagon-copying Test. Males showed impairment only in visuo-spatial short-term memory. ANOVA analysis revealed significant main effects of APOE ε4 status and sex on the MMSE, The Rey Auditory Verbal Learning Test, The Verbal Fluency, The Raven's Standard Progressive Matrices and The Pentagon-copying Test scores. Specifically, female APOE ε4 carriers performed consistently worse than other groups on many tasks. For depression, only an effect of sex emerged. Females scored higher besides APOE genotype.

Conclusions

These findings underscore the importance of considering both sex and APOE genotype when assessing cognitive performance in patients with temporal lobe epilepsy. The significant cognitive deficits we observed among females carrying the APOE ε4 allele highlight previously unexplored genetic and sex-related influences on cognition. This has potential implications for personalized therapeutic strategies, emphasizing the need for targeted assessment and intervention.

The association between APOE gene polymorphisms and the risk, characteristics, and prognosis of epilepsy: A systematic review and meta-analysis

OBJECTIVE

Epilepsy is one of the most common neurological diseases. Current evidence suggests that the apolipoprotein E (APOE) gene may be related to epilepsy. The purpose was to explore whether the APOE gene is associated with the risk, characteristics, and prognosis of epilepsy.

METHODS

The study was a systematic review and meta-analysis. We searched WANFANG, VIP, CNKI, Embase, CENTRAL, and Medline for relevant studies published in English and Chinese inception up to December 27, 2023. Studies containing both APOE genotypes or at least one type of APOE allele and epilepsy were included.

RESULTS

A total of 46 studies were included. Fourteen studies reported APOE genotypes and epilepsy risk (2539 patients and 2847 controls). The meta-analyses showed that the APOE 4 was higher in epilepsy (OR [95 % CI] = 1.32 [1.07, 1.62], I2 = 30 %), the APOE 2 was lower in epilepsy (OR [95 % CI] = 0.73 [0.62, 0.87], I2 = 0 %), and the APOE 3 didn't differ between epilepsy and controls (OR [95 % CI] = 1.01 [0.86, 1.19], I2 = 29 %). Our findings highlight that the risk of epilepsy is different depending on the subtype, with the APOE gene being more associated with temporal lobe epilepsy, drug-refractory epilepsy, and late-onset epilepsy. Patients with the ɛ4 allele have an earlier onset, worse cognition, and are more likely to have a history of febrile convulsion. No association between the ɛ4 allele and psychiatric symptoms and seizure-free after surgery.

INTERPRETATION

These findings will help inform the provision of epilepsy services, including clinical management an important option for epilepsy patients with cognitive impairment, temporal lobe epilepsy, late-onset epilepsy, and drug-refractory epilepsy. However, whether APOE gene testing should be used as a routine test in people with epilepsy remains to be determined.

Neuronal APOE4-induced Early Hippocampal Network Hyperexcitability in Alzheimer's Disease Pathogenesis

The full impact of apolipoprotein E4 (APOE4), the strongest genetic risk factor for Alzheimer's disease (AD), on neuronal and network function remains unclear. We found hippocampal region-specific network hyperexcitability in young APOE4 knock-in (E4-KI) mice which predicted cognitive deficits at old age. Network hyperexcitability in young E4-KI mice was mediated by hippocampal region-specific subpopulations of smaller and hyperexcitable neurons that were eliminated by selective removal of neuronal APOE4. Aged E4-KI mice exhibited hyperexcitable granule cells, a progressive inhibitory deficit, and E/I imbalance in the dentate gyrus, exacerbating hippocampal hyperexcitability. Single-nucleus RNA-sequencing revealed neuronal cell type-specific and age-dependent transcriptomic changes, including Nell2 overexpression in E4-KI mice. Reducing Nell2 expression in specific neuronal types of E4-KI mice with CRISPRi rescued their abnormal excitability phenotypes, implicating Nell2 overexpression as a cause of APOE4-induced hyperexcitability. These findings highlight the early transcriptomic and electrophysiological alterations underlying APOE4-induced hippocampal network dysfunction and its contribution to AD pathogenesis with aging.

Association between serum apolipoprotein E and cognitive function in Chinese patients with temporal lobe epilepsy

OBJECTIVE

To investigate the effect of serum apolipoprotein E (APOE) levels on cognitive function in patients with temporal lobe epilepsy (TLE).

METHODS

Clinical data were collected from 190 subjects including 110 TLE patients and 80 healthy people. Cognitive function was assessed using the Addenbrooke's Cognitive Examination Revised (ACE-R) scale. Serum levels of APOE were measured using ELISA kits. Genotyping of APOE in peripheral blood was detected by microarray hybridization.

RESULTS

Patients with TLE had significantly lower ACE-R total score, memory and verbal fluency scores compared to the healthy group. Serum levels of APOE were significantly higher in TLE patients than in the healthy subjects. Serum APOE levels were significantly negatively correlated with ACE-R total score, memory and verbal fluency scores. The cognitive function score of TLE with APOE ε4 allele was lower than that of TLE without APOE ε4 allele.

SIGNIFICANCE

Our study showed that serum APOE levels were higher in TLE patients than in the healthy population. And serum APOE levels were associated with cognitive dysfunction in TLE patients. APOE ε4 allele carriers have poor cognitive function in TLE patients.

Polygenic burden and its association with baseline cognitive function and postoperative cognitive outcome in temporal lobe epilepsy

OBJECTIVE

Demographic and disease factors are associated with cognitive deficits and postoperative cognitive declines in adults with pharmacoresistant temporal lobe epilepsy (TLE), but the role of genetic factors in cognition in TLE is not well understood. Polygenic scores (PGS) for neurological and neuropsychiatric disorders and IQ have been associated with cognition in patient and healthy populations. In this exploratory study, we examined the relationship between PGS for Alzheimer's disease (AD), depression, and IQ and cognitive outcomes in adults with TLE.

METHODS

202 adults with pharmacoresistant TLE had genotyping and completed neuropsychological evaluations as part of a presurgical work-up. A subset (n = 116) underwent temporal lobe resection and returned for postoperative cognitive testing. Logistic regression was used to determine if PGS for AD, depression, and IQ predicted baseline domain-specific cognitive function and cognitive phenotypes as well as postoperative language and memory decline.

RESULTS

No significant findings survived correction for multiple comparisons. Prior to correction, higher PGS for AD and depression (i.e., increased genetic risk for the disorder), but lower PGS for IQ (i.e., decreased genetic likelihood of high IQ) appeared possibly associated with baseline cognitive impairment in TLE. In comparison, higher PGS for AD and IQ appeared as possible risk factors for cognitive decline following temporal lobectomy, while the possible relationship between PGS for depression and post-operative cognitive outcome was mixed.

SIGNIFICANCE

We did not observe any relationships of large effect between PGS and cognitive function or postsurgical outcome; however, results highlight several promising trends in the data that warrant future investigation in larger samples better powered to detect small genetic effects.

Latest advances in mechanisms of epileptic activity in Alzheimer's disease and dementia with Lewy Bodies

Alzheimer's disease (AD) and dementia with Lewy bodies (DLB) stand as the prevailing sources of neurodegenerative dementia, impacting over 55 million individuals across the globe. Patients with AD and DLB exhibit a higher prevalence of epileptic activity compared to those with other forms of dementia. Seizures can accompany AD and DLB in early stages, and the associated epileptic activity can contribute to cognitive symptoms and exacerbate cognitive decline. Aberrant neuronal activity in AD and DLB may be caused by several mechanisms that are not yet understood. Hyperexcitability could be a biomarker for early detection of AD or DLB before the onset of dementia. In this review, we compare and contrast mechanisms of network hyperexcitability in AD and DLB. We examine the contributions of genetic risk factors, Ca2+ dysregulation, glutamate, AMPA and NMDA receptors, mTOR, pathological amyloid beta, tau and α-synuclein, altered microglial and astrocytic activity, and impaired inhibitory interneuron function. By gaining a deeper understanding of the molecular mechanisms that cause neuronal hyperexcitability, we might uncover therapeutic approaches to effectively ease symptoms and slow down the advancement of AD and DLB.

Alzheimer's disease and epilepsy: An increasingly recognized comorbidity

Both Alzheimer's disease (AD) and epilepsy are common chronic diseases in older people. Seizures and epileptiform discharges are very prevalent in AD and can occur since any stage of AD. Increasing evidence indicates that AD and epilepsy may be comorbid. Several factors may be related to the underlying mechanism of the comorbidity. Identifying seizures in patients with AD is a challenge because seizures are often clinically non-motor and may overlap with some AD symptoms. Not only seizures but also epileptiform discharges may exacerbate the cognitive decline in AD patients, highlighting the importance of early recognition and treatment. This review provides a comprehensive overview of seizures in AD from multiple aspects to provide more insight.

Neurobehavioural comorbidities of epilepsy: towards a network-based precision taxonomy

Cognitive and behavioural comorbidities are prevalent in childhood and adult epilepsies and impose a substantial human and economic burden. Over the past century, the classic approach to understanding the aetiology and course of these comorbidities has been through the prism of the medical taxonomy of epilepsy, including its causes, course, characteristics and syndromes. Although this 'lesion model' has long served as the organizing paradigm for the field, substantial challenges to this model have accumulated from diverse sources, including neuroimaging, neuropathology, neuropsychology and network science. Advances in patient stratification and phenotyping point towards a new taxonomy for the cognitive and behavioural comorbidities of epilepsy, which reflects the heterogeneity of their clinical presentation and raises the possibility of a precision medicine approach. As we discuss in this Review, these advances are informing the development of a revised aetiological paradigm that incorporates sophisticated neurobiological measures, genomics, comorbid disease, diversity and adversity, and resilience factors. We describe modifiable risk factors that could guide early identification, treatment and, ultimately, prevention of cognitive and broader neurobehavioural comorbidities in epilepsy and propose a road map to guide future research.

Genetic influence of Apolipoprotein E gene ε2/ε3/ε4 isoforms on odds of mesial temporal lobe epilepsy

OBJECTIVE

The potential correlation between the ε2/ε3/ε4 variants of the ApoE (Apolipoprotein E) gene and the odds of mesial temporal lobe epilepsy was investigated.

METHODS

The database searching for eligible studies was performed in October 2020. A series of pooling analyses were conducted.

RESULTS

We enrolled a total of twelve case-control studies for pooling. Within the pooling analysis of ε4, there was an increased risk of mesial temporal lobe epilepsy in cases under the models of carrier ε4 vs. ε3, ε3ε4 vs. ε3ε3, and ε3ε4+ε4ε4 vs. ε3ε3 [P < 0.05, odds ratio (OR) > 1], compared with controls. Moreover, we observed similar positive results in the subgroup analyses of "China" and "Population-based control" under the genetic models of ε4 (P < 0.05, OR > 1). Nevertheless, we did not detect the significant difference between the mesial temporal lobe epilepsy cases and controls in the pooling analyses of ε2 (all P > 0.05).

CONCLUSION

The ε3ε4 genotype of ApoE seems to be linked to the risk of mesial temporal lobe epilepsy for patients in China. More sample sizes are required to confirm the potential role of ApoE isoforms in the susceptibility to diverse types of epilepsy from different origins.

APOE4 Promotes Tonic-Clonic Seizures, an Effect Modified by Familial Alzheimer's Disease Mutations

Seizures are emerging as a common symptom in Alzheimer's disease (AD) patients, often attributed to high levels of amyloid β (Aβ). However, the extent that AD disease risk factors modulate seizure activity in aging and AD-relevant contexts is unclear. APOE4 is the greatest genetic risk factor for AD and has been linked to seizures independent of AD and Aβ. The goal of the present study was to evaluate the role of APOE genotype in modulating seizures in the absence and presence of high Aβ levels in vivo. To achieve this goal, we utilized EFAD mice, which express human APOE3 or APOE4 in the absence (EFAD-) or presence (EFAD+) of familial AD mutations that result in Aβ overproduction. When quantified during cage change day, we found that unlike APOE3, APOE4 is associated with tonic-clonic seizures. Interestingly, there were lower tonic-clonic seizures in E4FAD+ mice compared to E4FAD- mice. Restraint handing and auditory stimuli failed to recapitulate the tonic-clonic phenotype in EFAD mice that express APOE4. However, after chemical-induction with pentylenetetrazole, there was a higher incidence of tonic-clonic seizures with APOE4 compared to APOE3. Interestingly, the distribution of seizures to the tonic-clonic phenotype was higher with FAD mutations. These data support that APOE4 is associated with higher tonic-clonic seizures in vivo, and that FAD mutations impact tonic-clonic seizures in a paradigm dependent manner.

Cognitive decline in older adults with epilepsy: The Cardiovascular Health Study

OBJECTIVE

Cognitive decline is a major concern for older adults with epilepsy. Whether and how much faster older adults with epilepsy experience cognitive decline beyond expected age-related cognitive change remain unclear. We sought to estimate and compare rates of cognitive decline in older adults with and without epilepsy.

METHODS

The Cardiovascular Health Study is a population-based longitudinal cohort study of 5888 US adults aged 65+. Cognitive function was assessed annually with Modified Mini-Mental State Exam (3MS) and Digit Symbol Substitution Test (DSST). We used linear mixed models to estimate average rates of decline in 3MS and DSST scores by epilepsy status (prevalent, incident, or no epilepsy), adjusted for risk factors associated with cognitive decline.

RESULTS

The rate of decline in 3MS was significantly faster in prevalent epilepsy (P < .001) and after incident epilepsy (P = .002) compared with no epilepsy. Prevalent epilepsy and apolipoprotein E gene (APOE) ε4 (ApoE4) had a synergistic interaction, whereby prevalent epilepsy and ApoE4 together were associated with 1.51 points faster annual decline in 3MS than would be expected if prevalent epilepsy and ApoE4 did not interact (P < .001). Older adults with prevalent epilepsy had a significantly lower initial DSST score and faster rate of decline compared to those with no epilepsy (P < .001).

SIGNIFICANCE

Faster decline in global cognitive ability seen in this study validates concerns of patients. ApoE4 allele status was an effect modifier of the relationship between cognitive decline and prevalent epilepsy. Further research is warranted to explore biological mechanisms and possible interventions to mitigate cognitive decline.

Genetic Landscape of Common Epilepsies: Advancing towards Precision in Treatment

Epilepsy, a neurological disease characterized by recurrent seizures, is highly heterogeneous in nature. Based on the prevalence, epilepsy is classified into two types: common and rare epilepsies. Common epilepsies affecting nearly 95% people with epilepsy, comprise generalized epilepsy which encompass idiopathic generalized epilepsy like childhood absence epilepsy, juvenile myoclonic epilepsy, juvenile absence epilepsy and epilepsy with generalized tonic-clonic seizure on awakening and focal epilepsy like temporal lobe epilepsy and cryptogenic focal epilepsy. In 70% of the epilepsy cases, genetic factors are responsible either as single genetic variant in rare epilepsies or multiple genetic variants acting along with different environmental factors as in common epilepsies. Genetic testing and precision treatment have been developed for a few rare epilepsies and is lacking for common epilepsies due to their complex nature of inheritance. Precision medicine for common epilepsies require a panoramic approach that incorporates polygenic background and other non-genetic factors like microbiome, diet, age at disease onset, optimal time for treatment and other lifestyle factors which influence seizure threshold. This review aims to comprehensively present a state-of-art review of all the genes and their genetic variants that are associated with all common epilepsy subtypes. It also encompasses the basis of these genes in the epileptogenesis. Here, we discussed the current status of the common epilepsy genetics and address the clinical application so far on evidence-based markers in prognosis, diagnosis, and treatment management. In addition, we assessed the diagnostic predictability of a few genetic markers used for disease risk prediction in individuals. A combination of deeper endo-phenotyping including pharmaco-response data, electro-clinical imaging, and other clinical measurements along with genetics may be used to diagnose common epilepsies and this marks a step ahead in precision medicine in common epilepsies management.

Looking for indicative magnetic resonance imaging signs of hippocampal developmental abnormalities in patients with mesial temporal lobe epilepsy and healthy controls

OBJECTIVE

To evaluate the frequency of qualitative features for hippocampal developmental abnormalities (HiDeA) definition on magnetic resonance imaging (MRI) in mesial temporal lobe epilepsy (MTLE) patients and healthy controls, highlighting which were more sensitive and specific to the epileptic syndrome.

METHODS

We enrolled 93 healthy controls and 187 MTLE patients. Among patients, 133 were MRI-negative and 54 had hippocampal sclerosis (HS). Two blinded, trained investigators defined HiDeA if three signs were present, including at least one of the following: (1) globular hippocampal shape (HCS), (2) verticalized collateral sulcus, and (3) medial positioning of hippocampus (HCP). After evaluating the prevalence of HiDeA in MTLE and controls, we assessed the frequency of each sign. Then, we classified differences in type or number of HiDeA diagnostic features, calculating their sensitivity and specificity. Fisher exact test was used to assess statistical significance.

RESULTS

HiDeA was detected in 36 of 187 MTLE cases (19.25%) and in eight of 93 (8.6%) controls. In particular, HiDeA was present in 25 of 133 (18.8%) patients with MRI-negative MTLE. Among all visual criteria here considered, HCS showed higher sensitivity both in the MRI-negative MTLE group (88%) and in the HS-MTLE group (91%). HCP, thickened subiculum, and reduction of the upper horizontal portion of the parahippocampal gyrus (HCTH) signs demonstrated a 100% specificity in both groups. In healthy controls, HCS was confirmed to have the highest sensitivity (100%), whereas HCP showed the highest specificity (98.8%). All these criteria were statistically associated with HiDeA. Electroencephalographic focus was concordant with the HiDeA side in 52.2% of MTLE patients. An association was not found among signs of HiDeA and treatment responsiveness.

SIGNIFICANCE

We identified characteristic signs of HiDeA, such as HCTH or HCP, differentiating HiDeA features between MTLE and healthy controls. The identification of sensitive and, more importantly, specific criteria of HiDeA could be helpful to make a more confident visual diagnosis.

Neuropsychological profile of mild temporal lobe epilepsy

OBJECTIVE

In the current literature, whether patients with mild mesial temporal lobe epilepsy (mMTLE) have typical neurocognitive profile similar to patients with treatment-refractory seizures still remains unknown. The purpose of the present work was to analyze the neuropsychological profile in a group of consecutive patients with mMTLE.

METHODS

Forty consecutive patients whose conditions were diagnosed with mMTLE and 30 healthy controls (HC) were evaluated with an extensive neuropsychological battery. In addition, self-report questionnaires were also administered to evaluate the subjective impairments in prospective and retrospective memories. Finally, the levels of depression and anxiety were evaluated using the Beck Depression Inventory II (BDI-II) and the State-Trait Anxiety Inventory - Form Y1 (STAI-YI e 2).

RESULTS

Patients with mMTLE patients showed higher BDI-II scores (15.9 ± 13.9 vs 7.2 ± 6.7; p =, 002), and higher STAI-Y1 (41.2 ± 14.6 vs 32.6 ± 9.8; p =, 005) together with both objective and subjective memory deficits. Although BDI-II and STAI scores strongly correlated to the outcome in Rey Auditory Verbal Learning Test (RAVLT) and prospective and retrospective memory questionnaire (PRMQ) (p < 0.0021), these results did not change without depression scores.

CONCLUSION

We showed that a specific neurocognitive profile in patients with mMTLE exists. The neuropsychological features are mood depression, verbal memory immediate and delayed deficits, and subjective prospective and retrospective memory deficits.

Epileptic seizures in autosomal dominant forms of Alzheimer's disease

Alzheimer's disease (AD) is a heterogeneous neurodegenerative disorder and represents the most common form of dementia in the elderly. Mutations in genes encoding presenilin 1 (PSEN1), presenilin 2 (PSEN2) and amyloid precursor protein (APP) are responsible for early-onset familial AD (EOFAD). Several pieces of evidence report that patients with rare autosomal dominant forms of AD carry a significant risk to develop seizures. However, the molecular mechanisms linking epilepsy and AD are needed to be clarified: the pathophysiology of seizures in AD may be related to an increased production of amyloid-β (Aβ) peptide or structural alterations in neurons probably due to cerebrovascular changes, neurotransmitter or cytoskeletal dysfunctions. Seizures have traditionally been related to neuronal loss in the late stages of AD as a consequence of neurodegeneration, however, recent studies indicated that seizures may contribute to the emergence of AD symptoms in early stages of the disease, mainly in familial AD. So, a better understanding of possible common neural mechanisms might help to improve the clinical management of both conditions. This review aims to give a comprehensive overview and to analyze the association between epilepsy and EOFAD, focusing on possible overlapping pathological mechanisms.

WONOEP appraisal: Biomarkers of epilepsy-associated comorbidities

Neurologic and psychiatric comorbidities are common in patients with epilepsy. Diagnostic, predictive, and pharmacodynamic biomarkers of such comorbidities do not exist. They may share pathogenetic mechanisms with epileptogenesis/ictogenesis, and as such are an unmet clinical need. The objectives of the subgroup on biomarkers of comorbidities at the XIII Workshop on the Neurobiology of Epilepsy (WONOEP) were to present the state-of-the-art recent research findings in the field that highlighting potential biomarkers for comorbidities in epilepsy. We review recent progress in the field, including molecular, imaging, and genetic biomarkers of comorbidities as discussed during the WONOEP meeting on August 31-September 4, 2015, in Heybeliada Island (Istanbul, Turkey). We further highlight new directions and concepts from studies on comorbidities and potential new biomarkers for the prediction, diagnosis, and treatment of epilepsy-associated comorbidities. The activation of various molecular signaling pathways such as the "Janus Kinase/Signal Transducer and Activator of Transcription," "mammalian Target of Rapamycin," and oxidative stress have been shown to correlate with the presence and severity of subsequent cognitive abnormalities. Furthermore, dysfunction in serotonergic transmission, hyperactivity of the hypothalamic-pituitary-adrenocortical axis, the role of the inflammatory cytokines, and the contributions of genetic factors have all recently been regarded as relevant for understanding epilepsy-associated depression and cognitive deficits. Recent evidence supports the utility of imaging studies as potential biomarkers. The role of such biomarker may be far beyond the diagnosis of comorbidities, as accumulating clinical data indicate that comorbidities can predict epilepsy outcomes. Future research is required to reveal whether molecular changes in specific signaling pathways or advanced imaging techniques could be detected in the clinical settings and correlate with epilepsy-associated comorbidities. A reliable biomarker will allow a more accurate diagnosis and improved treatment of epilepsy-associated comorbidities.

Age of onset of mesial temporal lobe epilepsy with hippocampal sclerosis: the effect of apolipoprotein E and febrile seizures

PURPOSE

Mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS) is the most frequent pharmaco-resistant epilepsy. It has been associated with febrile seizures (FS) in childhood. Its aetiology remains unclear but genetic factors are involved. Apolipoprotein E (ApoE) is the main lipoprotein secreted in brain. It has a critical immunomodulatory function, influences neurotransmission and it is involved in repairing damaged neurons. ApoE ϵ4 is an isoform of ApoE with altered protein function, previously associated with refractoriness and early onset epilepsy. This study was undertaken to determine if ApoE isoforms are risk factors for MTLE-HS and influence clinical characteristics.

METHODS

A group of 188 MTLE-HS patients (101 F, 87 M, mean age = 44.7 ± 11.6 years, 100 with FS antecedents) was studied and compared with a group of 342 healthy individuals in a case-control genetic association study. Data were analysed with Pearson Chi-squared Test or Student's t test, as appropriated.

RESULTS

No differences in ApoE ϵ4 allelic frequencies between MTLE-HS patients and controls or between MTLE-HS subgroups were observed. Nevertheless, ApoE ϵ4 carriers had an earlier MTLE-HS onset (11.0 ± 7.9 years in ApoE ϵ4 carriers vs. 14.4 ± 11.2 years in ApoE ϵ4 non-carriers p < 0.05). Additionally, we observed that MTLE-HS patients with FS antecedents had a statistically significant early disease onset (11.5 ± 8.7 years in FS⁺ vs. 16.0 ± 12.1 years in FS^-, p < 0.01).

CONCLUSIONS

Our data show that ApoE ϵ4 and FS may not participate directly in etiopathogenic mechanisms of MTLE-HS but could hasten the disease development in predisposed individuals.

Apolipoprotein E ε4 Allele was Associated With Nonlesional Mesial Temporal Lobe Epilepsy in Han Chinese Population

Apolipoprotein E (APOE) gene has been implicated as one of the genes susceptible to temporal lobe epilepsy (TLE), but the association is inconsistent. We carried out a study to investigate the association of APOEε4 allele with a subtype of TLE-nonlesional mesial temporal lobe epilepsy (NLMTLE) in Han Chinese people.T he study consisted of total 308 NLMTLE patients and 302 controls in Han Chinese. The APOE polymorphisms were genotyped using polymerase chain reaction (PCR) DNA sequencing. We compared the frequency of APOEε4 allele and carrying status between NLMTLE patients and control subjects to test for the association of APOEε4 allele with NLMTLE clinical status. Carrying status of APOEε4 allele was significantly associated with the risk of NLMTLE. No effect of APOEε4 allele was found on the age of onset, duration of epilepsy, or frequency of seizure. Moreover, there was no association between APOEε4 allele and hippocampal sclerosis (HS) or febrile convulsion (FC) history.O ur study provided an evidence that APOEε4 allele was a possible risk factor for NLMTLE, and further study with a larger sample is needed to warrant this finding.

Preserved anterograde and remote memory in drug-responsive temporal lobe epileptic patients

PURPOSE

To investigate cognition, particularly anterograde and remote memory, in patients suffering from unilateral drug-responsive mesial temporal lobe epilepsy (mTLE) patients and to compare their performance with that observed in drug-resistant mTLE patients.

METHODS

Sixteen drug-responsive mTLE patients, with only infrequent seizures in their lifetime, were matched for demographic and clinical variables to 18 patients suffering from drug-resistant unilateral mTLE. A comprehensive neuropsychological examination, including baseline, anterograde memory tasks, and a large range of remote memory tests was carried out.

RESULTS

Patients with drug-responsive epilepsy obtained average scores on every anterograde memory test. Although in general, they obtained lower scores than the healthy controls on remote memory tests, the differences failed to reach significance. Moreover, the drug-responsive group performed significantly better than the drug-resistant group on anterograde recall tests and an episodic autobiographical memory test. Performance was not significantly different between the patient groups in personal semantics or memory for public events.

CONCLUSION

Our results show that a mild clinical course of mTLE with no cognitive deficits can occur notwithstanding hippocampal sclerosis. The differences in cognitive function between the two groups are likely due to distinct pathophysiology of the underlying cause of epilepsy. Drug-resistant seizures and cognitive deficits may be the consequence of a more severe underlying cerebral process. Better understanding of the variety of pathogenesis of mTLE could help to answer this open question.

Genetics of cognition in epilepsy

With the completion of the Human Genome Project and the advent of more advanced sequencing platforms capable of high throughput genotyping at reduced cost, research on the genetics/genomics of cognition has expanded rapidly over the past several decades. This has been facilitated even further by global consortia including HapMap, 1000 Genomes Project, ENCODE, and others, which have made information regarding genetic variation and genomic functional elements readily available to all researchers. Thus, the goal of this Targeted Review is not to provide an exhaustive review of the existing literature on the role of genetic factors in cognition. Rather, we will highlight some of the most consistent findings in this field, review the research in epilepsy to date, and provide a background within which to set forth unique opportunities epilepsy may provide to further elucidate the role of genetics in cognition.

A functional genetic variation of the 5-HTR2A receptor affects age at onset in patients with temporal lobe epilepsy

The 1354C>T polymorphism of the 5-hydroxytryptamine receptor 2A gene (5-HTR2A) was implicated in human memory performance. We investigated the relationship between this polymorphism and cognitive function in patients with temporal lobe epilepsy (TLE). We also evaluated if this polymorphism could influence the phenotype. There were 138 patients with TLE: 25% (34/138) of them found to be cognitively impaired, while the remaining 104 of 138 (75%) were found to be cognitively preserved after a comprehensive neuropsychological evaluation. dHPLC followed by DNA sequencing was used to detect the genetic variation. The distribution of 1354C>T did not differ between these two TLE groups, both in the comparison of genotype distribution (P= 0.177) and allele frequencies (P = 0.065). Nonetheless, patients with the T allele had a significantly earlier age at onset of the disease (P= 0.006). This effect was even stronger in patients with impaired memory (P= 0.00015). A second independent sample of 86 individuals with TLE satisfactorily confirmed the relationship between T allele and age at epilepsy onset. The results of this study have demonstrated that the T variant of 5-HTR2A may influence an earlier age of onset of TLE, especially in those with impaired memory. Nonetheless, this polymorphism has no major impact on memory functions in such TLE patients.

Emergence of a seizure phenotype in aged apolipoprotein epsilon 4 targeted replacement mice

The apolipoprotein ε4 allele is the strongest genetic risk factor for late-onset Alzheimer's disease (AD) and is associated with earlier age of onset. The incidence of spontaneous seizures has been reported to be increased in sporadic AD as well as in the early onset autosomal dominant forms of AD. We now report the emergence of a seizure phenotype in aged apolipoprotein E4 (apoE4) targeted replacement (TR) mice but not in age-matched apoE2 TR or apoE3 TR mice. Tonic-clonic seizures developed spontaneously after 5 months of age in apoE4 TR mice and are triggered by mild stress. Female mice had increased seizure penetrance compared to male mice, but had slightly reduced overall seizure severity. The majority of seizures were characterized by head and neck jerks, but 25% of aged apoE4 TR mice had more severe tonic-clonic seizures which occasionally progressed to tonic extension and death. Aged apoE4 TR mice progressed through pentylenetetrazol-induced seizure stages more rapidly than did apoE3 TR and apoE2 TR mice. Electroencephalographic (EEG) recordings revealed more frequent bursts of synchronous theta activity in the hippocampus of apoE4 TR mice than in apoE2 TR or apoE3 TR mice. Cortical EEG recordings also revealed sharp spikes and other abnormalities in apoE4 TR mice. Taken together, these findings demonstrate the emergence of an age-dependent seizure phenotype in old apoE4 TR mice in the absence of human amyloid-β peptide (Aβ) overexpression, suggesting increased central nervous system neural network excitability.

Evidence that an APOE ε4 'double whammy' increases risk for Alzheimer's disease

Temporal lobe epilepsy (TLE) is associated with some of the same neuropathological features as those reported for early stages of typical Alzheimer's disease (AD). The APOE ε4 allele is associated with a gene-dose-dependent increase in AD risk and in the severity of amyloid-β (Aβ) pathology. In a study published in the current BMC Medicine, Sue Griffin and colleagues studied markers of brain resilience in the amputated temporal lobes of TLE patients. They discovered compelling evidence that the APOE ε3 isoform in TLE patients is apparently more neuroprotective from Aβ toxicity than is the APOE ε4 isoform, as shown by the reduced levels of neuronal damage, glial activation, and expression of IL-1α in the APOE ε3/ε3 brains. This result points to a new property of APOE isoforms: not only are APOE ε4 alleles associated with increased brain amyloid plaque burden, but these alleles are also apparently inferior to APOE ε3 alleles in conveying resistance to Aβ neurotoxicity. This 'double whammy' result opens up a new direction for studies aimed at elucidating the relevant neurobiological activities of APOE isoforms in the pathogenesis of AD.

Genetics of temporal lobe epilepsy: a review

Temporal lobe epilepsy (TLE) is usually regarded as a polygenic and complex disorder. To understand its genetic component, numerous linkage analyses of familial forms and association studies of cases versus controls have been conducted since the middle of the nineties. The present paper lists genetic findings for TLE from the initial segregation analysis to the most recent results published in May 2011. To date, no genes have been clearly related to TLE despite many efforts to do so. However, it is vital to continue replication studies and collaborative attempts to find significant results and thus determine which gene variant combination plays a definitive role in the aetiology of TLE.

Association of apolipoprotein E polymorphisms with temporal lobe epilepsy in a Chinese Han population

Apolipoprotein E (ApoE) has been implicated as one of the susceptibility genes for temporal lobe epilepsy (TLE). Previous studies indicate that ApoE ɛ4 is associated with several disease-related traits including the increased risk of late posttraumatic seizures, earlier onset of TLE, refractory complex partial seizures, and postictal confusion. Contradictory data were also reported regarding the association between ApoE polymorphisms and TLE. The present study was designed to investigate whether ApoE ɛ4 is a risk factor for TLE and the above clinical variables, as well as to determine whether -491A/T polymorphism may independently alter the risk for TLE in a Chinese Han population. The ApoE and -491A/T polymorphisms were genotyped in 558 controls and 735 patients including 560 TLE patients using polymerase chain reaction-restriction fragment length polymorphism. A significant association was detected between prior trauma and the ApoE ɛ4 allele in TLE patients. However, no significant differences were observed in the genotype and haplotype distributions and allele frequencies of these two polymorphisms between cases and controls. Furthermore, there were no significant associations between these two polymorphisms and the other clinical variables examined. The study illustrates that the ApoE ɛ4 allele may be involved in the development of TLE in those patients with prior trauma in the Chinese Han population.

ApoE, MemorE, and EpilepsE

ApoE- ∊4 Is Associated with Reduced Memory in Long-Standing Intractable Temporal Lobe Epilepsy. Busch RM, Lineweaver TT, Naugle RI, Kim KH, Gong Y, Tilelli CQ, Prayson RA, Bingaman W, Najm IM, Diaz-Arrastia R. Neurology 2007;68(6):409–414. OBJECTIVE: To investigate the relationship between the apolipoprotein (ApoE) 4 allele and memory performance (verbal and nonverbal) in patients with medically intractable temporal lobe epilepsy (TLE) who underwent temporal lobectomy. METHODS: Presurgical and postsurgical memory performance was examined in 87 adult patients with TLE (4 = 22; non-4 = 65) to determine whether the expression of ApoE-4 may be associated with memory performance in this population and to examine how this relationship may be affected by duration of epilepsy. RESULTS: There was a significant interaction between ApoE-4 status and duration of epilepsy such that 4 carriers with a long duration of epilepsy demonstrated the poorest memory performance on both verbal and nonverbal measures. This relationship was observed both before and after temporal lobectomy, with little change in test performance over time. CONCLUSIONS: The ApoE-4 allele interacts with longstanding seizures to affect memory performance, both verbal and nonverbal, in patients with medically intractable temporal lobe epilepsy.

ApoE epsilon4 genotype and the age at onset of temporal lobe epilepsy: a case-control study and meta-analysis

In order to investigate the role of ApoE epsilon4 as a modifier of the age at onset of temporal lobe epilepsy (TLE), we performed a molecular epidemiology study in 78 patients with mesial temporal lobe epilepsy and hippocampal sclerosis. Genotyping was done by a PCR-RFLP assay. In order to better estimate the role of this variant as a modifier of the age at onset, we also performed a systematic review of the literature. We included our results into a meta-analysis along with data available from seven published studies with 728 patients that looked into the role of ApoE epsilon4 in TLE. We found that ApoE epsilon4 carriers in our population had a non-significant earlier age of epilepsy onset than non-carriers. The meta-analysis confirmed this finding, showing that ApoE epsilon4 carriers had epilepsy onset almost 4 years earlier than non-carriers (mean difference 5.15 years; CI 95% 2.08-6.22; p=0.001). In conclusion, the ApoE epsilon4 isoform is a genetic factor that might influence the age at onset of TLE.

Cerebrospinal fluid apolipoprotein E concentration decreases after seizure

PURPOSE

In epilepsy, many studies were focus on apoE gene polymorphism and found APOE epsilon4 to be associated with earlier onset of temporal lobe epilepsy. There is not any study about apoE in cerebrospinal fluid (CSF) of epileptic patients, so we detect the CSF-apoE and determine whether it is changed after seizure.

METHODS

A total of 60 epileptic patients and 28 subjects with no evidence of any neurological diseases were studied. The concentrations of CSF-apoE were detected with enzyme-linked immunosorbent assay.

RESULTS

The CSF-apoE levels in epilepsy and control group were 5.78+/-2.15 mg/l and 13.60+/-12.11 mg/l, and there were statistical difference. In epilepsy group, the CSF-apoE concentration was 6.53+/-2.55 mg/l in male patients, and 4.98+/-1.21 mg/l in female. In secondary epilepsy group was 5.06+/-1.31 mg/l, and in idiopathic epilepsy was 6.04+/-2.34 mg/l. In different seizure types groups, including complex partial seizure (CPS), secondarily generalized tonic-clonic seizure (SGTC), generalized tonic-clonic seizure (GTCS), and absence seizure (AS), the mean concentrations of CSF-apoE were 6.62+/-3.13 mg/l, 5.21+/-1.22 mg/l, 5.00+/-1.09 mg/l and 7.25+/-1.88 mg/l, respectively.

CONCLUSIONS

CSF-apoE concentration decreases after seizures, correlated with the gender, etiological factor and seizure types.

APOE-ε4 is not associated with cognitive impairment in relapsing—remitting multiple sclerosis

The objective of this article was to assess the association between apolipoprotein E (APOE)-ε4 and cognitive impairment (CI) in relapsing—remitting multiple sclerosis (RRMS). The APOE genotype was assessed in 85 RRMS cases (58 females, mean age 43 ± 8.4 years, mean disease duration 15.8 ± 9.6 years, mean Expanded Disability Status Scale (EDSS) 1.7 ± 1.0). Cognitive functioning was evaluated in the whole sample using Rao’s Brief Repeatable Battery (BRB). Performance on each test was assessed by applying the normative values for the Italian population. In a subgroup of 50 patients, a brain magnetic resonance (MR) study was performed including measurement of T2 lesion volumes (T2LV), neocortical volume (NCV) and normalized brain volume (NBV). The relationship between APOE genotype, CI and MR variables was assessed through univariate and multivariate logistic regression models. CI, most commonly involving complex attention and verbal memory tasks, was found in 28 cases (33%). We identified a total of 19 ε4carriers (22.4%), who did not differ from non-carriers regarding clinical and demographic characteristics. The presence of the ε4 genotype was associated with neither CI (p = 0.28) nor impairment on each neuropsychological test (p > 0.32; corrected for age, gender, disease duration, EDSS, depression and fatigue). The APOE genotype and CI were also not related in the subgroup of younger patients (age < 45 years; p > 0.9). Moreover, CI was related to higher T2LV (p = 0.008) and lower NCV (p = 0.006). In conclusion, in our sample CI was associated with higher subcortical damage and cortical atrophy but not with APOE-ε4 genotype. The role of APOE-ε4 as a possible biomarker in multiple sclerosis is still questionable.

Candidate genes for temporal lobe epilepsy: a replication study

The objective of this study is to replicate previously published results regarding the involvement of several susceptibility genes in temporal lobe epilepsy (TLE): interleukin 1beta (IL-1beta), interleukin 1beta (IL-1alpha), interleukin 1RA (IL-1RA), apolipoprotein E (ApoE) and prodynorphin (PDYN). We used a case-control approach comparing several polymorphisms within these candidate genes between unrelated TLE patients and matched controls. We were thus able to confirm the role of ApoE, IL-1alpha and IL-1RA genes in TLE disease, but failed to confirm the involvement of IL-1beta and PDYN. This failure should be interpreted with caution, as this may be due to the small size of our study groups and the resultant lack of statistical power.

Growing old with epilepsy: the neglected issue of cognitive and brain health in aging and elder persons with chronic epilepsy

The purpose of this review is to examine what is known about cognitive and brain aging in elders with chronic epilepsy. We contend that much remains to be learned about the ultimate course of cognition and brain structure in persons with chronic epilepsy and concern appears warranted. Individuals with chronic epilepsy are exposed to many risk factors demonstrated to be associated with abnormal cognitive and brain aging in the general population, with many of these risk factors present in persons with chronic epilepsy as early as midlife. We suggest that a research agenda be developed to systematically identify and treat known modifiable risk factors in order to protect and promote cognitive and brain health in aging and elder persons with chronic epilepsy.

Association between the M129V variant allele of PRNP gene and mild temporal lobe epilepsy in women

Specific variations in the prion protein gene (PRNP) are associated with, and prevalent in patients with intractable temporal lobe epilepsy (TLE) and influence the surgical outcome. We investigated whether or not the PRNP gene is a susceptibility gene in temporal lobe epileptic patients with mild epilepsy. We systematically screened the entire open reading frame of the PRNP gene and evaluated the genetic contribution of the functional PRNP M129V polymorphism in 289 patients with mild TLE compared with a neurologically unaffected age and sex matched control group (n=272). Statistical analysis revealed a moderate difference in the distribution at codon 129 of the PRNP gene between sporadic mild TLE patients and healthy controls (p=0.036; OR=1.30; 95% CI=1.01-1.68). Although, there was no statistically significant difference in the genotype distribution within the study groups (p=0.101), a further analysis showed that the 129V allele was highly represented only in women with TLE compared with control group (p=0.006, OR=1.632; 95%CI=1.15-2.31). This is the first publication of data that support the hypothesis that the common methionine/valine polymorphism at codon 129 of the PRNP gene may modify the susceptibility of women to mild TLE.

New antiepileptic drugs that are second generation to existing antiepileptic drugs

In the last decade, 10 new antiepileptic drugs (AEDs) have been introduced that offer appreciable advantages in terms of their favourable pharmacokinetics, improved tolerability and lower potential for drug interactions. However, despite the large therapeutic range of old and new AEDs, approximately 30% of the patients with epilepsy are still not seizure free and, consequently, there is a substantial need to develop new AEDs. The new AEDs currently in development can be divided into two categories: drugs with completely new chemical structures such as lacosamide (formally harkoseride), retigabine, rufinamide and talampanel; and drugs that are derivatives or analogues of existing AEDs that can be regarded as second-generation or follow-up compounds of established AEDs. This article focuses on the second category and thus critically reviews the following second-generation compounds: eslicarbazepine acetate or BIA-2-093 and 10-hydroxy carbazepine (carbamazepine derivatives); valrocemide and NPS 1776 (isovaleramide; valproic acid derivatives); pregabalin and XP13512 (gabapentin derivatives); brivaracetam (ucb 34714) and seletracetam (ucb 44212; levetiracetam derivatives); and fluorofelbamate (a felbamate derivative). In addition, a series of valproic acid derivatives that are currently in preclinical stage has also been evaluated because some lead compounds of this series have a promising potential to become new antiepileptics and CNS drugs. For any of these follow-up compounds to become a successful second generation to an existing AED, it has to be more potent, safer and possess favourable pharmacokinetics, including low potential for pharmacokinetic and pharmacodynamic drug interactions.

Association of refractory complex partial seizures with a polymorphism of ApoE genotype

Apolipoprotein E (ApoE) is a constituent of many types of lipoproteins that play a role in metabolism of cholesterol and lipids in the body as well as in the brain. ApoE is synthesised in astrocytes and microglia and enter to neurons through LDL, LRP and VLDL receptors. Recently it was shown that ApoE is also produced in neurons. ApoE has a role in modulating learning and memory, structural plasticity, mobilization of cholesterol in repair, growth and maintenance of myelin and neuronal membranes during development and aging, and cell death after ischemic, convulsive, or other type of brain injury. The aim of this research was to investigate the possible association of ApoE gene polymorphism with the development of resistance to pharmacological therapy in patients with partial complex seizures with or without secondary generalization. In this prospective matched-pair controlled study, 60 patients with cryptogenic epilepsy with complex partial seizures, with or without secondary generalization, who have been suffering for five or more years, were studied. The first group comprised 30 patients refractory to the current therapy, while the second group consisted of patients with well-controlled seizures. The refractory and non-refractory groups of patients differed significantly in their phenotypes. Phenotype E3/4 was six times more frequent in refractory group than among non-refractory group. The lack of response was shown to be significantly associated with the presence of epsilon4 allele. This study provided evidence that the presence of epsilon4 allele is more often associated with a lack of response to current antiepileptic drugs as compared to epsilon2 and epsilon3 alleles.