Differential effects of first antiepileptic drug application on cognition in lesional and non-lesional patients with epilepsy

Neuroimaging of memory in frontal lobe epilepsy

In a large percentage of epilepsies, seizures have focal onset. These epilepsies are associated with a wide range of behavioral and cognitive deficits sometimes limited to the functions encompassed within the ictal onset zone but, more frequently, expanding beyond it. The presence of impairments associated with neuroanatomical areas outside of the ictal onset zone suggests distal propagation of epileptic activity via brain networks and interconnected whole-brain neural circuitry. In patients with frontal lobe epilepsy (FLE), using functional magnetic resonance imaging (fMRI) to identify deficits in working, semantic, and episodic memory may provide a lens through which to understand typical and atypical network organization. A network approach to focal epilepsy is relevant in these patients because of the frequently noted early age of seizure onset. Early seizure-related disruption in healthy brain development may result in a significant brain reorganization, development of compensation-related mechanisms of dealing with function abnormalities and disruptions, and the propagation of epileptic activity from the focus to widespread brain areas (functional deficit zones). Benefits of a network approach in the study of focal epilepsy are discussed along with considerations for future neuroimaging studies of patients with FLE.

Reference ranges for antiepileptic drugs revisited: a practical approach to establish national guidelines

BACKGROUND AND OBJECTIVE

Laboratories sometimes use different reference ranges for the same antiepileptic drug (AED), particularly for new and poorly investigated drugs. This may contribute to misunderstandings, concerns or inappropriate dose changes, which in turn may affect therapeutic effect, drug safety or treatment adherence. Therefore, the Norwegian Association of Clinical Pharmacology wished to update and harmonize the reference ranges for AEDs and establish national guidelines for Norway.

METHODS

A working group collected information on the reference ranges used by Norwegian laboratories for all commonly used AEDs. These reference ranges were compared to recent recommendations by the International League Against Epilepsy, current literature, applicable clinical studies, reference ranges used by leading Northern European epilepsy centers outside of Norway, and routine data derived from Norwegian laboratory databases.

RESULTS

Reference ranges varied between laboratories for four of 23 available AEDs (lamotrigine, valproate, eslicarbazepine and oxcarbazepine). For four AEDs (brivaracetam, perampanel, stiripentol and sulthiame), reference ranges had not previously been established. In total, 13 reference ranges were either harmonized, updated or newly established. No changes were applied to the remaining 10 AEDs.

CONCLUSION

Updated and harmonized reference ranges are now available for 22 of the 23 AEDs available in Norway. The exception is vigabatrin (reference range not applicable). Revision of reference ranges is an important part of pharmacovigilance of AEDs and must be a continuous process based on current literature and clinical experience.

Newly diagnosed epilepsy: cognitive outcome after 12 months

PURPOSE

Cognitive impairment is a common comorbidity of epilepsy; however, relatively little research has been undertaken to investigate how cognitive problems develop in adults who are newly diagnosed. This study aimed to investigate changes in cognitive performance in adults with new-onset epilepsy 12 months after diagnosis compared with healthy volunteers.

METHODS

One hundred forty-seven people with epilepsy (PWE) were assessed using a comprehensive neuropsychological test battery before they started treatment and after 12 months. Cognitive change scores were compared with 69 healthy volunteers who were also assessed at baseline and after 12 months.

KEY FINDINGS

At 12 month follow-up, PWE had significantly poorer change scores for 9 of the 16 variables. For the majority of these measures, PWE had subtle declines in performance, whereas healthy volunteers improved. Poorer performance on some measures was associated with treatment with topiramate, generalized seizures and, interestingly, achieving an immediate 12-month seizure remission.

SIGNIFICANCE

After controlling for statistically confounding factors, people with newly diagnosed epilepsy had a different cognitive trajectory compared with healthy volunteers from the general population. Memory, psychomotor speed, and higher executive functioning were the domains most vulnerable to change over a 12-month period.

Cognitive function in juvenile myoclonic epilepsy

In this study, we examined 35 patients with juvenile myoclonic epilepsy (JME) and 35 healthy volunteers. We used tests of cognitive performance (mini mental state examination, verbal and visual memory, visuospatial, frontal function, attention). In the JME group, we examined age, sex, family history, education level, age of seizure onset, seizure types, characteristics of EEG, duration of the therapy, drug dose and level, and verbal IQ level. Additionally, patients initially diagnosed as JME and patients who were initially under inappropriate drug therapy because of misdiagnosis were compared. As a result, we found statistically significant differences between JME patients and the control group with respect to verbal and visual memory. Furthermore, JME patients had impaired frontal and visuospatial function compared with the control group. We detected negative effects of younger age, family history, and absence seizures on cognitive function in JME patients.

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.

Behavioral Aspects of Frontal Lobe Epilepsy

There is growing interest in disorders of behavior, personality, and mood associated with focal epilepsies, though the neuropsychological and behavioral or psychiatric aspects of epilepsy have usually been treated separately. The causes of behavioral disorders in patients with focal epilepsies are multifactorial, though the positive effects of seizure control on behavior suggest that state dependency is a major contributing factor. Patients with temporal lobe epilepsy manifest depression, anxiety, neuroticism, and social limitations, as well as impaired memory. By contrast, studies of cognitive function in patients with frontal lobe epilepsy show executive dysfunctions in response selection/initiation and inhibition, as well as cognitive impairment, hyperactivity, conscientiousness, obsession, and addictive behaviors.

Comparative double blind clinical trial of phenytoin and sodium valproate as anticonvulsant prophylaxis after craniotomy: efficacy, tolerability, and cognitive effects

OBJECTIVE

To determine the efficacy, tolerability, and impact on quality of life and cognitive functioning of anticonvulsant prophylaxis with phenytoin or sodium valproate in patients after craniotomy.

METHODS

A prospective, stratified, randomised, double blind single centre clinical trial was performed, comparing two groups of 50 patients each, who underwent craniotomy for different pathological conditions and who were treated for 1 year after surgery with either 300 mg phenytoin/day or 1500 mg sodium valproate/day. During the study period patients were seen in the outpatient clinic at 1.5, 3, 6, and 12 months, when medical history, adverse events, and drug plasma concentrations were evaluated. Neuropsychological functioning and quality of life were assessed on the last three visits. In cases of a seizure an EEG was performed, drug plasma concentration assessed, and medication subsequently increased.

RESULTS

Of the 100 included patients 14 (seven in each group) experienced one or more postoperative seizures. Severity of the seizures was comparable in the two groups. In all patients, drug plasma concentrations were in the low or subtherapeutic ranges at the time of the first postoperative seizure. Five patients in the phenytoin group and two in the valproate group had to stop their treatment due to drug related adverse events. Sixty patients completed the 12 month period. Analysis of neuropsychological and quality of life data showed no significant differences.

CONCLUSION

For efficacy, tolerability, impact on cognitive functioning, and quality of life, no major differences were found between phenytoin and valproate prophylaxis. Valproate is an alternative for anticonvulsant prophylaxis in patients after craniotomy.

Rectal diazepam: pitfalls of excessive use in refractory epilepsy

INTRODUCTION

The rectal administration of diazepam (DZP) has provided a safer existence to many epilepsy patients and their carers, when prolonged or serial seizures are present. However, in patients with frequent seizures, chronic, intermittent over-administration may occur, particularly in the presence of multihandicaps.

METHODS

Six patients who experienced untoward effects from excessive rectal DZP are reported. In two patients, serial plasma levels of DZP and its active metabolites were monitored.

RESULTS

Three patients exhibited a pattern of cyclic reappearance of seizures, interrupted by rectal DZP, followed by sedation and gradual awakening. The intervals were approximately 4 days. The three other patients had variable and complex symptoms with serial seizures and alternating states of tension, apathy, and sleepiness. The plasma levels of DZP and desmethyl-DZP showed rapid fluctuations.

CONCLUSION

When rectal DZP is prescribed, chronic and excessive administration should be avoided. Fluctuating plasma-levels may probably support a cyclic reappearance of seizures in some patients. The combination of high bolus doses and a rapid drug clearance due to enzyme inducing co-medication may probably increase the risk for rebound reactions. Toxic, withdrawal, and epileptic symptoms may be intermingled and difficult to manage. A replacement strategy in the form of a prophylactic, oral, low dose benzodiaepine regimen may facilitate the discontinuation of this prescription pattern. Adequate counselling and medically appropriate, written directions for the use of rectal DZP is mandatory.

Side effects from increased doses of carbamazepine on neuropsychological and posturographic parameters of humans

Patients taking anticonvulsant drugs display a broad spectrum of side-effects. Particularly, in the beginning of treatment and with increasing doses of carbamazepine, side effects such as dizziness, ataxia, drowsiness and reduction of alertness occur, which improve some days after the dose has reached a stable level. Our aim was to find objective parameters for grading these side effects and to differentiate between neurophysiological and neuropsychological side effects of carbamazepine in a clinical situation. Twenty-two patients with trigeminal neuralgia were included for a follow-up study with increasing carbamazepine doses (0 mg to 600 mg). The effect of carbamazepine on postural stability was quantified by posturography. Different neuropsychological tests to study cognitive effects of carbamazepine were performed. The composite equilibrium score showed a significant reduction of postural stability with increasing doses of carbamazepine. In sensory analysis the somatosensory ratio was significantly influenced by increased doses of carbamazepine during the study. Mean reaction time of tonic alertness and physical alertness varied significantly with different doses of carbamazepine. There was a significant influence in patients attention during trail making tests and divided attention tests with increase in carbamazepine. In conclusion our observations show that the rate of change of carbamazepine doses is an important determinant of cognitive and motor functions in the phase of increasing doses.

Differential impairments of spatial memory and social behavior in two models of limbic epilepsy

To explore memory impairments in temporal lobe epilepsy, we used two experimental models in the rats: (a) kainate-induced status epilepticus (SE) resulting in excitotoxic damage and in later spontaneous seizures; and (b) amygdala kindling, known to induce no lesions (or only minor) and neuronal reorganization. Long-term effects of these models on memory were investigated with a spatial learning task in a radial-arm maze, and a social interaction test that implies degree of short-term memory. An histological analysis was made to determine neuronal damage or loss caused by epileptic activity in brain regions that could be related to memory functions. Kainate-induced epilepsy produced large memory deficits in animals tested 5 months after the injection. The rats showed severe lesions in amygdala and hippocampus and piriform and entorhinal cortex. Spatial memory was strongly diminished. The social memory test was severely impaired, probably due to the extent of amygdala injury, which is known to disturb social behavior. On the contrary, kindled rats showed no evident lesion in any brain region and displayed performances as good as those of controls in both tests. These experiments demonstrated that memory deficits appear to be related to the severity of neuronal damage in limbic areas, and the ability to develop seizures (permanence) is not solely responsible for these memory disturbances.

Cognitive side-effects of chronic antiepileptic drug treatment: a review of 25 years of research

Over 90 investigations have been conducted over the past 25 years to determine what effect AEDs have on cognition. No satisfactory answer to this problem can be given, however, chiefly because there is a paucity of studies that pass fairly basic standards of methodology, design and analysis that apply to the evaluation of any clinical research. This severely limits the precision of statements regarding cognitive AED effects. More particularly, there is little reason to recommend any of the first-line AEDs as the AED of choice from the standpoint of cognitive side-effects. On the basis of the present review we are not in a position to provide a straightforward answer to the most pertinent question, i.e., whether AEDs in therapeutic doses have any cognitive effects at all, good or bad. If we reduce the available database to monotherapy studies in epilepsy that use control group data for comparison, employ an appropriate form of repeated measures analysis, and provide sufficient information, very few studies remain that are directly relevant to this issue. This in itself precludes definitive conclusions. As can be seen from Table 9, absolute effects of CBZ and VPA have been examined in epilepsy patients three times each (in four studies), PB has been examined two times, PHT only once. In addition to the paucity of relevant data, there are miscellaneous validity concerns in all of these studies, one recurring theme being that of inconclusive 'no effect' findings with small samples. Without firm knowledge about absolute effects, relative effects, and particularly their absence, are difficult to interpret. Employing the above criteria (except that concerning controls), ten epilepsy studies that address this issue remain (Table 10). It is instructive to look at the number of times particular AEDs have been compared against each other (Table 11). CBZ has been compared to PHT five times, other comparisons occur only once or twice. Again, this is hardly a basis for definitive statements, particularly because validity concerns occur here as well. Recurring concerns here are scattered significant findings that tend to disappear if adjustment of the significance level for multiple comparisons is done, and inconclusive 'no difference' findings with small samples. Even if there were no conclusion validity concerns in individual studies, comparison between studies would be complicated by considerable variation in the subjects studied. Five of the studies summarized in Tables 8 and 9 use children as subject, nine use adults; results obtained in one group may not be generalizable to the other. Also, subjects may be newly diagnosed cases, or patients already on chronic treatment. The latter choice of subjects may be a factor working against detecting cognitive side-effects, as the damage (if any) may already have been done before the beginning of the trial. In addition, a wide variety of assessment tools have been used to search for cognitive effects of AEDs, ranging from measurements of reaction time and motor speed to intelligence tests. Some of these may be more sensitive to drug induced changes in cognition than others. Still, the tentative overall picture emerging from the creme de la creme of research on cognitive AED effects is that differences in cognitive profiles may not be very large. An important point here, of course, is the magnitude of the difference one considers worth detecting. Very few studies have attempted to answer this question. In the majority of studies we examined, a large treatment effect was anticipated implicitly, judging from the generally limited sample sizes. The choice of a study design based on a large treatment effect size may not always be appropriate, though. Of course, one could argue that it is only large effects that may be of practical or clinical significance anyways [30] and that effects of lesser magnitude are of no consequence. However, there are many examples where even a small benefit of one treatme

Cognitive and behavioral effects of antiepileptic drugs

All antiepileptic drugs (AEDs) have the potential for adverse effects on cognition and behavior. Most of the major AEDs, administered in therapeutic doses, cause little or no cognitive or behavioral impairment in group studies. However, individual variability is considerable, and some patients do not tolerate low serum levels, whereas others tolerate high levels without subjective or objective effects. In the past, carbamazepine (CBZ) and valproate (VPA) have been reported to have the fewest adverse cognitive and behavioral effects in children and adults. However, several recent, well-controlled studies have not found significant differences between the effects of phenytoin (PHT) and those of CBZ or VPA. Greater adverse effects have been found for phenobarbital (PB). However, we must use environmentally relevant measures of cognitive and behavioral functioning to measure effects on daily functioning. Future studies must define cognitive and behavioral toxicity in subpopulations (e.g., post-traumatic epilepsy, mental retardation, depression) and with the new AEDs.

The diversity of epilepsy in adults with severe developmental disabilities: age at seizure onset and other prognostic factors

There is usually a causal relationship between epilepsy and mental retardation when they coexist. The pathogenetic period of the underlying brain disorder and the time of seizure onset may, however, be widely separated. In 63 institutionalized mentally retarded epilepsy patients, 41% had seizure onset prior to the age of 2, 30% between the age of 2 and 20, and as many as 29% after the age of 20. Whereas uncontrolled epilepsy and cerebral palsy were frequently present in the group of early onset, most patients with adult onset had well controlled epilepsy, and none had cerebral palsy. Five of the 18 patients with adult onset epilepsy had Down's syndrome; in three of them, concomitant dementia was evident. In most patients with adult onset, however, no recent or current etiological factors for seizures were evident, except for their stable intellectual deficits. The incidence of adult onset epilepsy in the institution in 10 years markedly exceeded the expected rate. Twenty-three patients had achieved a prolonged remission of seizures and discontinued antiepileptic treatment. Sixty per cent of them remained seizure-free after at least two years. The mentally retarded should not unduly be subjected to drugs with potential central nervous side-effects.

Postictal courses of cognitive deficits in focal epilepsies

Patients with epileptic seizures frequently complain of long-lasting cognitive impairment after a seizure. We evaluated this issue in 31 patients with epileptic seizures of a frontal (n = 8) or temporal lobe origin [right temporal lobe (RTL) n = 8/left temporal lobe (LTL) n = 15]. Seizures were secondarily generalized in 18 patients. Computerized testing of verbal and nonverbal recognition memory was performed before the seizure, directly after postictal reorientation, and 30 min and 1 h later. Repeated testing of 14 healthy persons served as control. The following results were obtained: Depending on seizure generalization, postictal reorientation times were 1-45 min. Frontal lobe seizures showed no effect on postictal memory performances, but verbal and visual recognition memory was significantly decreased after temporal lobe seizures. Decrease in either verbal or visual memory and time of recovery were related to lateralization of seizure onset. Functional recovery after reorientation lasted 30 min to 1 h. The decrease in performance was more severe after generalized seizures. Decision times during memory performance were not significantly affected by the seizures. Temporal lobe seizures lead to circumscribed and long-lasting memory deficits, which can be assumed to affect patients' capabilities seriously. Pre- and postictal testing is a useful tool for determining postictal cognitive impairment and in determining the site of seizure onset.