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OBJECTIVE: Levetiracetam (LEV) is an effective antiseizure medicine, but 10%-20% of people treated with LEV report psychiatric side-effects, and up to 1% may have psychotic episodes. Pharmacogenomic predictors of these adverse drug reactions (ADRs) have yet to be identified. We sought to determine the contribution of both common and rare genetic variation to psychiatric and behavioral ADRs associated with LEV. METHODS: This case-control study compared cases of LEV-associated behavioral disorder (n = 149) or psychotic reaction (n = 37) to LEV-exposed people with no history of psychiatric ADRs (n = 920). All samples were of European ancestry. We performed genome-wide association study (GWAS) analysis comparing those with LEV ADRs to controls. We estimated the polygenic risk scores (PRS) for schizophrenia and compared cases with LEV-associated psychotic reaction to controls. Rare variant burden analysis was performed using exome sequence data of cases with psychotic reactions (n = 18) and controls (n = 122). RESULTS: Univariate GWAS found no significant associations with either LEV-associated behavioural disorder or LEV-psychotic reaction. PRS analysis showed that cases of LEV-associated psychotic reaction had an increased PRS for schizophrenia relative to contr ols (p = .0097, estimate = .4886). The rare-variant analysis found no evidence of an increased burden of rare genetic variants in people who had experienced LEV-associated psychotic reaction relative to controls. SIGNIFICANCE: The polygenic burden for schizophrenia is a risk factor for LEV-associated psychotic reaction. To assess the clinical utility of PRS as a predictor, it should be tested in an independent and ideally prospective cohort. Larger sample sizes are required for the identification of significant univariate common genetic signals or rare genetic signals associated with psychiatric LEV ADRs.

Juvenile myoclonic epilepsy (JME) is a common syndrome of genetic generalized epilepsies (GGEs). Linkage and association studies suggest that the gene encoding the bromodomain-containing protein 2 (BRD2) may increase risk of JME. The present methylation and association study followed up a recent report highlighting that the BRD2 promoter CpG island (CpG76) is differentially hypermethylated in lymphoblastoid cells from Caucasian patients with JME compared to patients with other GGE subtypes and unaffected relatives. In contrast, we found a uniform low average percentage of methylation (

SUMMARY Purpose: Levetiracetam (LEV) is a highly effective antiepileptic agent. A clinically relevant psychiatric complication of LEV treatment, however, is the provocation of irritability and aggression. Recent behavioral research indicates that personality traits may predispose to these side effects. To assess the genetic basis of the adverse psychotropic profile of LEV, a candidate gene-based two-stage association study was conducted. Methods: Polymorphisms were a priori selected according to their relevance for impulsivity and reactive-impulsive aggression. Based on data from both stages, a Bonferroni-corrected joint meta-analysis was computed. Key Findings: Stage 1 analysis included 290 patients with epilepsy and revealed a higher load of adverse psychotropic side effects of LEV in patients carrying genetic variants associated with decreased dopaminergic activity: rs1611115 (dopamine-b-hydroxylase, DBH), rs4680 (catechol-O-methyltransferase, COMT), and rs1800497 (dopamine receptor D2-associated ANKK1 TAQ-1A). Stage II analysis including 100 patients with epilepsy, and joint meta-analysis confirmed the effect of the rs1800497 polymorphism (Bonferroni corrected significance of the joint meta-analysis, p = 0.0096). Significance: Confirming the suggestion from behavioral observations that patients might be predisposed to develop irritation and aggression under treatment with LEV, the findings provide first evidence of an association of genetic variation in dopaminergic activity and the risk for psychiatric complications of LEV treatment. Replication and further work is required to prove a true causal relationship. Overall, the pharmacogenomic approach to behavioral side effects may provide a future tool to predict adverse psychotropic effects related to antiepileptic drugs.

Summary Purpose: Recent clinical studies raised concern of a cognitive teratogenicity of the major antiepileptic drug valproate. To investigate possible cerebral correlates, we established a forced self-application schedule by diluting valproate in the drinking water of pregnant Wistar rats. Methods: After application of medium (MD) and high doses (HDs) with mean daily intakes of about 470 and 720 mg/kg during the entire pregnancy, we analyzed effects on offspring performance in a series of behavioral paradigms as well as brain volumetric changes by magnetic resonance imaging (MRI). Results: While high dosages with peak serum concentrations slightly above 100 μg/ml induced early decrements in general activity and deficits in learning and memory, medium dosages led to improved watermaze performance in 30-day-old rats. MRI analyses indicated increased hippocampal volumes in the MD condition, whereas in the HD condition significantly decreased cortical and brainstem volumes were registered. Cortical volume reduction was correlated with spatial acuity in the watermaze. Conclusions: The results indicate that effects of valproate in utero on offspring cognitive capabilities might depend on total drug load differentially affecting cerebral development during adolescence in the rat.

Summary Partial deletions of the RBFOX1 gene encoding the neuronal splicing regulator have been reported in a range of neurodevelopmental diseases including idiopathic/genetic generalized epilepsy (IGE/GGE), childhood focal epilepsy, and self-limited childhood benign epilepsy with centrotemporal spikes (BECTS, rolandic epilepsy), and autism. The protein regulates alternative splicing of many neuronal transcripts involved in the homeostatic control of neuronal excitability. Herein, we examined whether structural deletions affecting RBFOX1 exons confer susceptibility to common forms of juvenile and adult focal epilepsy syndromes. We screened 807 unrelated patients with sporadic focal epilepsy, and we identified seven hemizygous exonic RBFOX1 deletions in patients with sporadic focal epilepsy (0.9%) in comparison to one deletion found in 1,502 controls. The phenotypes of the patients carrying RBFOX1 deletions comprise magnetic resonance imaging (MRI)–negative epilepsy of unknown etiology with frontal and temporal origin (n = 5) and two patients with temporal lobe epilepsy with hippocampal sclerosis. The epilepsies were largely pharmacoresistant but not associated with intellectual disability. Our study extends the phenotypic spectrum of RBFOX1 deletions as a risk factor for focal epilepsy and suggests that exonic RBFOX1 deletions are involved in the broad spectrum of focal and generalized epilepsies.

Summary: Purpose: After pilocarpine-induced epilepsy in rats, volumetric magnetic resonance imaging (MRI) reveals significant morphologic changes in functionally relevant structures of the brain. To relate structural changes to functional alteration, we studied the correlation of regional brain atrophy (e.g., of the hippocampus) with lesion-induced learning deficits in the Morris water maze. Methods: MRI experiments were performed on an MR scanner at 4.7 Tesla. For volumetric analysis, various cerebral structures were segmented in horizontal and coronal T2-weighted MR images. Before the MRI investigations, animals were trained for 10 days in a Morris water maze. Results: Volumetric MRI revealed a significant loss in hippocampal size in both the dorsal and ventral parts, correlated with an increase in ventricular size. Furthermore, significant losses were found in the relative size of thalamus, putamen, cortex, and the combined areas of perirhinal, entorhinal, and piriform cortices adjacent to the hippocampus. A significant correlation of learning performance in the Morris water maze with the relative hippocampal area and not with other areas tested was observed in pilocarpine-treated animals. Conclusions: The data provide a quantitative analysis of functionally relevant structural alterations in rats with chronic epilepsy. Water maze performance of pilocarpine-treated animals correlates with the degree of hippocampal but not with the degree of cortical damage, demonstrating the potential of this method for the investigation of cognitive impairments in relation to cerebral changes. In addition, the data point to an important role of even the residual hippocampus in memory formation. Ke yW ords: Temporal lobe epilepsy—Pilocarpine—MRI— Volumetry—Rat—Hippocampus—Learning—Water maze.

Summary: Purpose: For the antiepileptic drug (AED) topiramate (TPM), neuroprotective effects have been reported in models of focal cerebral ischemia and experimental status epilepticus, but the putative mechanism of action has remained elusive. Methods: We studied the effects of TPM on mitochondrial function in the pilocarpine rat model of chronic epilepsy and in isolated mitochondria from rat brain. Results: TPM treatment in status epilepticus at doses ranging from 20 to 100 mg/kg considerably improved the survival of rats and improved CA1 and CA3 pyramidal cell survival in a dose-dependent manner. This treatment increased the activity of mitochondrial respiratory chain complex I in the CA1 and CA3 pyramidal subfields and resulted in lower seizure frequencies in chronic epileptic rats. In vitro investigations of the action of TPM on isolated rat brain mitochondria ruled out any direct effects of the drug on mitochondrial oxidative phosphorylation bu tr evealed a protective effect on hippocampal mitochondria against an external calcium challenge. This can explain its observed neuroprotective action in the concentration range tested. The in vitro effects of TPM on the calcium handling of isolated brain mitochondria was found to be comparable to the action of cyclosporin A. Conclusions: The neuroprotective action of TPM seems to be directly related to its inhibitory effect on the mitochondrial permeability transition pore. Ke yW ords: Hippocampus— Topiramate—Mitochondrial function—Neuroprotection— Epilepsy—Pilocarpine-treated rat—Mitochondrial permeability transition pore (MPT).

Summary: Purpose: Interictal [ 18 F]fluorodeoxyglucose (FDG) positron emission tomography (PET) demonstrates temporal hypometabolism in the epileptogenic zone of 60–90% of patients with temporal lobe epilepsy. The pathophysiology of this finding is still unknown. Several studies failed to show a correlation between hippocampal FDG-PET hypometabolism and neuronal cell loss. Because FDG is metabolized by hexokinase bound to the outer mitochondrial membrane, we correlated the glucose-oxidation capacity of hippocampal subfields obtained after surgical resection with the corresponding hippocampal presurgical FDG-PET activity. Methods: In 16 patients with electrophysiologically confirmed temporal lobe epilepsy, we used high-resolution respirometry to determine the basal and maximal glucose-oxidation rates in 400-m-thick hippocampal subfields obtained after dissection of human hippocampal slices into the CA1 and CA3 pyramidal subfields and the dentate gyrus. Results: We observed a correlation of the FDG-PET activity with the maximal glucose-oxidation rate of the CA3 pyramidal subfields (rp 0.7, p 0.003) but not for the regions CA1 and dentate gyrus. In accordance with previous studies, no correlation of the FDG-PET to the neuronal cell density of CA1, CA3, and dentate gyrus was found. Conclusions: The interictal hippocampal FDG-PET hypometabolism in patients with temporal lobe epilepsy is correlated to the glucose-oxidation capacity of the CA3 hippocampal subfield as result of impaired oxidative metabolism. Key Words: Temporal lobe epilepsy—FDG-PET—Mitochondrial oxidative phosphorylation.

OBJECTIVE: To ascertain possible determinants of carbamazepine (CBZ)- and oxcarbazepine (OXC)-induced hyponatremia in a large cohort of people with epilepsy.METHODS: We collected data on serum sodium levels in people with epilepsy who were attending a tertiary epilepsy center while on treatment with CBZ or OXC. We defined hyponatremia as Na+ ≤134 mEq/L and severe hyponatremia as Na+ ≤128 mEq/L.RESULTS: We identified 1,782 people who had used CBZ (n = 1,424) or OXC (n = 358), of whom 50 were treated with both drugs. Data on sodium level measurements were available in 1,132 on CBZ and in 289 on OXC. Hyponatremia occurred in 26% of those taking CBZ and 46% of those taking OXC. This was severe in 7% in the CBZ group and 22% in the OXC group. Hyponatremia was symptomatic in 48% and led to admissions in 3%. Age over 40 years, high serum levels of CBZ and OXC, and concomitant use of other antiepileptic drugs were the main risk factors for hyponatremia in both treatment groups. Female patients on OXC were at a higher risk than male patients of hyponatremia. The risk of hyponatremia on CBZ was significantly associated with the risk of hyponatremia on OXC within a subgroup that used both drugs consecutively.SIGNIFICANCE: Hyponatremia is a common problem in people taking CBZ or OXC. Regular ascertainment of sodium levels in those taking either drug is recommended and results should be acted on.

Levetiracetam (LEV) is a highly effective antiepileptic agent. A clinically relevant psychiatric complication of LEV treatment, however, is the provocation of irritability and aggression. Recent behavioral research indicates that personality traits may predispose to these side effects. To assess the genetic basis of the adverse psychotropic profile of LEV, a candidate gene-based two-stage association study was conducted.Polymorphisms were a priori selected according to their relevance for impulsivity and reactive-impulsive aggression. Based on data from both stages, a Bonferroni-corrected joint meta-analysis was computed.Stage 1 analysis included 290 patients with epilepsy and revealed a higher load of adverse psychotropic side effects of LEV in patients carrying genetic variants associated with decreased dopaminergic activity: rs1611115 (dopamine-β-hydroxylase, DBH), rs4680 (catechol-O-methyltransferase, COMT), and rs1800497 (dopamine receptor D2-associated ANKK1 TAQ-1A). Stage II analysis including 100 patients with epilepsy, and joint meta-analysis confirmed the effect of the rs1800497 polymorphism (Bonferroni corrected significance of the joint meta-analysis, p = 0.0096).Confirming the suggestion from behavioral observations that patients might be predisposed to develop irritation and aggression under treatment with LEV, the findings provide first evidence of an association of genetic variation in dopaminergic activity and the risk for psychiatric complications of LEV treatment. Replication and further work is required to prove a true causal relationship. Overall, the pharmacogenomic approach to behavioral side effects may provide a future tool to predict adverse psychotropic effects related to antiepileptic drugs.

Summary Purpose: In patients with mesial temporal lobe epilepsy (MTLE) it remains an unresolved issue whether the interictal decrease in N-acetyl aspartate (NAA) detected by proton magnetic resonance spectroscopy (1H-MRS) reflects the epilepsy-associated loss of hippocampal pyramidal neurons or metabolic dysfunction. Methods: To address this problem, we applied high-resolution 1H-MRS at 14.1 Tesla to measure metabolite concentrations in ex vivo tissue slices from three hippocampal subfields (CA1, CA3, dentate gyrus) as well as from the parahippocampal region of 12 patients with MTLE. Results: In contrast to four patients with lesion-caused MTLE, we found a large variance of NAA concentrations in the individual hippocampal regions of patients with Ammon's horn sclerosis (AHS). Specifically, in subfield CA3 of AHS patients despite of a moderate preservation of neuronal cell densities the concentration of NAA was significantly lowered, while the concentrations of lactate, glucose, and succinate were elevated. We suggest that these subfield-specific alterations of metabolite concentrations in AHS are very likely caused by impairment of mitochondrial function and not related to neuronal cell loss. Conclusions: A subfield-specific impairment of energy metabolism is the probable cause for lowered NAA concentrations in sclerotic hippocampi of MTLE patients.