Current discoveries on the cognitive effects of antiepileptic drugs

Effects of antiepileptic drugs on mRNA levels of BDNF and NT-3 and cell neogenesis in the developing rat brain

Epilepsy is a common neurological disorder that occurs more frequently in childhood than in adulthood. Antiepileptic drugs (AEDs) which are used to treat seizures in pregnant women, infants, and young children may cause cognitive impairment or other uncertain injury. However, the exact mechanisms responsible for adverse effects of AEDs in the developing brain are still not clear. In the present study, we investigate the effects of AEDs on mRNA levels of brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3), cell neogenesis and mossy fiber sprouting (MFS) in the developing rat brain. Long-term treatment with Phenobarbital (40mg/kg), valproate (100mg/kg) and topiramate (40mg/kg) reduces BDNF and NT-3 mRNA expression in the developing brain, while lamotrigine reduces mRNA expression only at high dose level (80mg/kg). Cell neogenesis only increases in the rats treated with valproate and lamotrigine. And no differences are observed between the control group and the AEDs-treated groups in the Timm scores of the CA3 region and supragranular region. Our findings present some possible mechanisms to explain why different AEDs cause different cognitive impairment.

Decreased glutamate receptor binding and NMDA R1 gene expression in hippocampus of pilocarpine-induced epileptic rats: neuroprotective role of Bacopa monnieri extract

The potential for antiepileptic drugs to negatively impact cognitive abilities has generated renewed interest in herbal drugs and formulations in the treatment of epilepsy. Bacopa monnieri is one such widely used revitalizing herb that purportedly strengthens nervous function and also possesses memory-enhancing, antioxidative, antiepileptic, and anti-inflammatory properties. We investigated the neuroprotective role of B. monnieri extract in alteration of glutamate receptor binding and gene expression of NMDA R1 in hippocampus of temporal lobe epileptic rats. In association with pilocarpine-induced epilepsy, there was significant downregulation of NMDA R1 gene expression and glutamate receptor binding without any change in its affinity. B. monnieri treatment of epileptic rats significantly reversed the expression of NMDA R1 and glutamate receptor binding alterations to near-control levels. Also, in the epileptic rats, we measured a significant increase in the activity of glutamate dehydrogenase, which neared the control level after B. monnieri treatment. The therapeutic effect of B. monnieri was also observed in the Morris water maze experiment. These data together indicate the neuroprotective role of B. monnieri extract in glutamate-mediated excitotoxicity during seizures and cognitive damage occurring in association with pilocarpine-induced epilepsy.

Effects of antiepileptic drugs on learning as assessed by a repeated acquisition of response sequences task in rats

Patients with epilepsy can have impaired cognitive abilities. Antiepileptic drugs (AEDs) may contribute to the cognitive deficits observed in patients with epilepsy, and have been shown to induce cognitive impairments in healthy individuals. However, there are few systematic data on the effects of AEDs on specific cognitive domains. We have previously demonstrated that a number of AEDs can impair working memory and attention. The purpose of the present study was to evaluate the effects of AEDs on learning as measured by a repeated acquisition of response sequences task in nonepileptic rats. The GABA-related AEDs phenobarbital and chlordiazepoxide significantly disrupted performance by shifting the learning curve to the right and increasing errors, whereas tiagabine and valproate did not. The sodium channel blockers carbamazepine and phenytoin suppressed responding at higher doses, whereas lamotrigine shifted the learning curve to the right and increased errors, and topiramate was without significant effect. Levetiracetam also shifted the learning curve to the right and increased errors. The disruptions produced by triazolam, chlordiazepoxide, lamotrigine, and levetiracetam were qualitatively similar to the effects of the muscarinic cholinergic receptor antagonist scopolamine. The present results indicate that AEDs can impair learning, but there are differences among AEDs in the magnitude of the disruption in nonepileptic rats, with drugs that enhance GABA receptor function and some that block sodium channels producing the most consistent impairment of learning.

Effects of antiepileptic drugs on attention as assessed by a five-choice serial reaction time task in rats

Patients with epilepsy can have impaired cognitive abilities. Antiepileptic drugs (AEDs) may contribute to the cognitive deficits observed in patients with epilepsy, and have been shown to induce cognitive impairments in healthy individuals. However, there are few systematic data on the effects of AEDs on specific cognitive domains. We have previously evaluated a number of AEDs with respect to their effects on working memory. The purpose of the present study was to evaluate the effects of AEDs on attention as measured by five-choice serial reaction time behavior in nonepileptic rats. The GABA-related AEDs triazolam, phenobarbital, and chlordiazepoxide significantly disrupted performance by increasing errors of omission, whereas tiagabine, valproate, and gabapentin did not. The sodium channel blocker carbamazepine increased errors of omission at relatively high doses, whereas the sodium channel blockers phenytoin, topiramate, and lamotrigine were without significant effect. Levetiracetam had no effect on attention. The disruptions produced by triazolam, phenobarbital, chlordiazepoxide, and carbamazepine were similar in magnitude to the effects of the muscarinic cholinergic receptor antagonist scopolamine. The present results indicate that AEDs can disrupt attention, but there are differences among AEDs in the magnitude of the disruption in nonepileptic rats, with drugs that enhance GABA receptor function producing the most consistent disruption of attention.

Optimizing antiepileptic drug therapy in the elderly

OBJECTIVE

To review and evaluate the medical literature concerning antiepileptic drug (AED) therapy in elderly patients.

DATA SOURCES

A MEDLINE search (1982-December 2004) was conducted. Bibliographies of the articles identified were also reviewed, and an Internet search engine was used to identify additional pertinent references.

STUDY SELECTION AND DATA EXTRACTION

Clinical studies and reviews were evaluated, and relevant information was included.

DATA SYNTHESIS

The elderly have the highest incidence of seizures among all age groups. Complex partial seizures are the most common, followed by primary generalized tonic-clonic seizures. An accurate diagnosis may prove difficult because of a low suspicion of epilepsy in the elderly and other diseases that may mimic seizures. Most AEDs are approved for treatment of elderly patients who have partial and tonic-clonic seizures. However, a number of age-related variables should be addressed when selecting an appropriate AED. Age-dependent differences in pharmacokinetics and pharmacodynamics of AEDs must be taken into account. Drug-drug interactions must be considered since elderly people often take multiple medications. The ultimate factor that often determines AED selection is tolerability.

CONCLUSIONS

Numerous factors must be considered in treating elderly patients for seizures, but maximizing the ability of patients to tolerate drug therapy is often the basis for AED selection. Special consideration should be made along several lines, including elderly patients' cognitive functioning and their tendency to respond to lower AED concentrations.

Treatment of epilepsy in adults: expert opinion, 2005

RATIONALE

Over the past decade, there has been a proliferation of new therapies for the treatment of epilepsy. Faced with this growing list of options, clinicians must decide what therapy, or combination of therapies, is best for a given individual. Although controlled clinical trials exist for each treatment option, the answer to these questions may remain unclear. In 2000, a survey of expert opinion was done to address questions concerning which treatment options might be best in a number of clinical situations. We surveyed a group of US epileptologists again in 2004 and compared the results of the two surveys.

METHODS

We sent a questionnaire on the treatment of adolescent and adult epilepsy syndromes to a group of opinion leaders in the field of epilepsy. The questions were formatted to simulate real-world clinical situations in the treatment of symptomatic localization related epilepsy (SLRE) and idiopathic generalized epilepsy (IGE). The experts were asked to rate treatment options based on a modified RAND 9-point scale (with "9" most appropriate and "1" least appropriate). Statistical analysis of data was performed as defined by the expert consensus method. The results were used to develop user-friendly recommendations concerning overall treatment strategies and choice of specific medications.

RESULTS

Of the 48 experts to whom the survey was sent, 43 (90%) responded; 29 (67%) of the respondents had also participated in the first survey. For initial monotherapy for IGE (generalized tonic-clonic [GTC], absence, and myoclonic seizures), valproate was rated as treatment of choice. For IGE-GTC seizures, lamotrigine and topiramate were also identified as usually appropriate for initial monotherapy. For IGE-absence seizures, ethosuximide was also a treatment of choice, and lamotrigine was usually appropriate. For SLRE, the experts were again asked to rate treatment options based on seizure type: simple partial seizures (SPS), complex partial seizures (CPS), and secondarily generalized tonic-clonic seizures (SGTC). In SLRE-SPS and SLRE-SGTC, carbamazepine and oxcarbazepine were treatments of choice, with lamotrigine and levetiracetam also usually appropriate. In SLRE-CPS, carbamazepine, lamotrigine. and oxcarbazepine were treatments of choice, while levetiracetam was also usually appropriate. For women who are pregnant or trying to conceive, lamotrigine was treatment of choice for both syndrome types. In the elderly, whether medically stable or ill, the treatment of choice was lamotrigine, while levetiracetam was also usually appropriate (along with gabapentin for persons with comorbid medical illness). In persons with HIV and epilepsy, lamotrigine and levetiracetam were usually appropriate. In people with both epilepsy syndromes who have depression, lamotrigine was treatment of choice. In a person with seizures and renal disease, lamotrigine was usually appropriate for both syndromes, with valproate also usually appropriate for IGE. In patients with hepatic disease, levetiracetam and lamotrigine were usually appropriate for IGE; in SLRE, levetiracetam was treatment of choice, with gabapentin also usually appropriate.

CONCLUSIONS

Although the panel of experts reached consensus on many treatment options, there are limitations to these types of data. Despite this, the expert consensus method concisely summarizes expert opinion, and this opinion may be helpful in situations in which the medical literature is scant or lacking. The information in this report should be evaluated in conjunction with evidence-based findings.

Effects of antiepileptic drugs on working memory as assessed by spatial alternation performance in rats

Patients with epilepsy can have impaired cognitive abilities. Many factors contribute to this impairment, including the adverse effects of antiepileptic drugs (AEDs). However, there are few systematic data on the effects of AEDs on specific cognitive domains, such as working memory. The purpose of the present study was to evaluate the effects of AEDs on working memory as measured by delayed spatial alternation behavior in nonepileptic rats. The GABA-related AEDs triazolam and phenobarbital significantly disrupted performance, whereas tiagabine, valproate, and gabapentin did not. The sodium channel blockers carbamazepine and topiramate produced modest but significant disruption of performance, whereas the effects of lamotrigine were not significant and phenytoin produced a modest but significant improvement in performance but at doses that abolished responding in some animals. Levetiracetam had no effect on working memory. In contrast, ethosuximide significantly disrupted working memory. The disruptions produced by triazolam and phenobarbital were similar in magnitude to the effects of the muscarinic antagonist scopolamine. The present results indicate that AEDs can disrupt working memory, but there are differences among AEDs in the magnitude of the disruption that do not appear to be correlated with mechanism of action.

Tratamento de epilepsia: consenso dos especialistas brasileiros

Epilepsia é uma condição muito freqüente em todo o mundo. Na última década, várias opções terapêuticas surgiram ou foram aprimoradas. O principal método utilizado para decisão terapêutica baseia-se nos estudos randomizados, que representam o maior nível de evidência. Entretanto, mesmo estes estudos são passíveis de críticas e em alguns casos o tratamento de escolha permanece controverso. Nestas situações, a opinião dos especialistas, na área da epileptologia, com maior experiência clínica, passa a ter grande valor. O presente estudo tem como principal objetivo elaborar um consenso de tratamento das epilepsias, através da opinião de experts brasileiros no assunto. Este consenso poderá auxiliar na criação de manuais e estratégias para o tratamento de determinadas síndromes epilépticas, de acordo com os padrões socioeconômicos brasileiros.

Posttraumatic epilepsy: neuroradiologic and neuropsychological assessment of long-term outcome

PURPOSE

We sought to detect the incidence and the risk factors of posttraumatic epilepsy (PTE) in rehabilitation patients; to define the influence of PTE for late clinical and functional outcome; and to assess the cognitive and behavioral features of the patients with PTE.

METHODS

Patients were examined with (a) cognitive and behavioral examinations, which included a clinical interview and psychometric tests performed by an expert clinical psychologist; (b) single-photon emission computed tomography (SPECT) and magnetic resonance imaging (MRI); and (c) functional evaluation including the Glasgow Outcome Scale (GOS) and the Functional Independence Measure (FIM).

RESULTS

Of the 143 patients examined in this study, in 27 (19%), seizures developed after a mean time from trauma of 11.9 +/- 8.6 months. The occurrence of PTE was significantly correlated with the hypoperfusion in temporal lobes (p < 0.004), the degree of hydrocephalus (p < 0.04), the evidence of intracerebral hematoma (p < 0.01), and operative brain injury (p < 0.001). Patients with epilepsy showed a significantly higher incidence of personality disorders than did patients without epilepsy. The uninhibited behavior, irritability, and agitated and aggressive behavior were significantly more frequent and severe in PTE patients. The psychometric tests intended to explore memory, language, intelligence, attention, and spatial cognition did not show any significant difference between those with and without epilepsy. PTE also was significantly correlated with a worse functional outcome 1 year after the trauma.

CONCLUSIONS

The degrees of hydrocephalus and of hypoperfusion in the temporal lobes are significant risk factors for late PTE. Another main finding of our study is the absence of influence of epilepsy on cognitive disorders; its influence on neurobehavioral disorders and functional outcome is discussed.

Childhood epilepsy in relation to mental handicap and behavioural disorders

Epidemiological studies indicate that there is a high rate of mental retardation and behavioural problems in children with epilepsy. In some cases both the epilepsy and the mental retardation will have a common cause, such as a metabolic disorder or brain trauma. However, in other children, the epilepsy itself may cause either temporary or permanent learning problems. When permanent learning disability can be prevented it is important to treat the epilepsy early and effectively. Children with specific learning difficulties and memory problems can benefit greatly from appropriate management. There are many causes of behavioural disturbance in children with epilepsy. These causes include the epilepsy itself, treatment of the epilepsy, reactions to the epilepsy, associated brain damage/dysfunction and causes that are equally applicable to children who do not have epilepsy. Identifying the cause or causes in each child allows rational management to be provided. Antiepileptic treatment with medication or surgery can either improve the situation or make matters worse. The treatment should be tailored to the needs of the individual child. If surgery is required, there is a strong argument for performing this early in life, both to allow the greatest opportunity for brain plasticity and also to allow the child full benefit from the important developmental and educational years, without the problems that can be associated with the epilepsy. Skilled management of children with epilepsy who have mental retardation and/or behavioural problems can be very rewarding both for the family and for the professionals involved.