Altered cognitive functioning in children with idiopathic epilepsy receiving valproate monotherapy

Altered functional connectivity in default mode network in absence epilepsy: a resting-state fMRI study

Dysfunctional default mode network (DMN) has been observed in various mental disorders, including epilepsy (see review Broyd et al. [2009]: Neurosci Biobehav Rev 33:279–296). Because interictal epileptic discharges may affect DMN, resting-state fMRI was used in this study to determine DMN functional connectivity in 14 healthy controls and 12 absence epilepsy patients. To avoid interictal epileptic discharge effects, testing was performed within interictal durations when there were no interictal epileptic discharges. Cross-correlation functional connectivity analysis with seed at posterior cingulate cortex, as well as region-wise calculation in DMN, revealed decreased integration within DMN in the absence epilepsy patients. Region-wise functional connectivity among the frontal, parietal, and temporal lobe was significantly decreased in the patient group. Moreover, functional connectivity between the frontal and parietal lobe revealed a significant negative correlation with epilepsy duration. These findings indicated DMN abnormalities in patients with absence epilepsy, even during resting interictal durations without interictal epileptic discharges. Abnormal functional connectivity in absence epilepsy may reflect abnormal anatomo-functional architectural integration in DMN, as a result of cognitive mental impairment and unconsciousness during absence seizure.

Valproate as a mainstay of therapy for pediatric epilepsy

This article reviews relevant pharmacologic and clinical information gathered for valproate since it was introduced into clinical practice 37 years ago and the application of this information for the treatment of childhood epilepsy. Valproate is available for oral and parenteral use. Oral forms are almost completely bioavailable but the rate of absorption varies between formulations. The Chrono tablet formulation has not been adapted for children aged <6 years, in whom the oral solution or syrup, requiring two or three daily administrations, has been used until recently. A new formulation specifically adapted for children, Chronosphere, administrated once or twice daily, is a modified-release formulation of valproate that minimizes fluctuations in serum drug concentrations during a dosage interval. Plasma protein binding is 80-94% and tends to decrease with increasing drug concentration. Valproate elimination is markedly decreased in newborns compared with older children and adults. Elimination by glucuronidation only becomes fully effective by the age of 3-4 years. In children aged 2-10 years receiving valproate, plasma clearances are 50% higher than those in adults. Over the age of 10 years, pharmacokinetic parameters approximate those of adults. Valproate can increase plasma concentrations of concomitant drugs, such as phenobarbital and lamotrigine, by inhibiting their metabolism. As a result of its broad spectrum of efficacy in a wide range of seizure types and epilepsy syndromes, valproate is a drug of choice for children with newly diagnosed epilepsy (focal or generalized), idiopathic generalized epilepsy, epilepsies with prominent myoclonic seizures or with multiple seizure types, and photosensitive epilepsies. In the group of cognitive epilepsies, in which severe spike and wave discharges are accompanied by cognitive deterioration, valproate, ethosuximide, or both should be tested before using corticosteroids. In comparative trials with carbamazepine, phenytoin, and phenobarbital in focal epilepsy and with ethosuximide in absence epilepsy, valproate was as effective and showed a favorable tolerability profile, with minimal adverse cognitive and CNS effects. The low potential for paradoxical seizure aggravation and the long-term efficacy of the drug are additional important factors that contribute to its excellent profile. Intravenous valproate may be effective for the treatment of convulsive and non-convulsive status epilepticus that is refractory to conventional drugs. In infants, potential benefits should be carefully weighed against the risk of liver toxicity. Gastrointestinal intolerance is a relatively frequent, dose-related adverse effect of the drug in children. Bodyweight increase and tremor may be observed in older children and adolescents. Despite the challenge of newer drugs, valproate remains a gold standard antiepileptic drug for the treatment of children.

Lamotrigine as first-line drug in childhood absence epilepsy: a clinical and neurophysiological study

To investigate to which extent lamotrigine (LTG) may be effective and tolerated as a monotherapy for the treatment of newly diagnosed childhood absence seizures and, secondly, to evaluate the efficacy of this drug on the circadian interictal generalized epileptiform discharges, 20 consecutive newly diagnosed patients (five males, 15 females), aged 3-10 years (mean 6.9 years), affected by childhood absence epilepsy, were administered LTG as first-line drug at the initial dose of 0.5 mg/kg/day for 2 weeks, followed by 1.0 mg/kg/day for an additional 2 weeks. Thereafter, doses have been increased in 1-mg/kg/day increments up to 9-12 mg/kg/day in accordance with the clinical response. Each patient underwent an ambulatory (24 h) EEG monitoring before starting LTG therapy (time 0) and during the maintenance period at the end of LTG titration (time 1). After a mean follow-up period of 10.8 months (range 3-28 months), a 100% seizure control was obtained in 11 children (55.5%), a more than 75% seizure decrease was present in four (20%), and a >50% seizure decrease in five (25%), with a mean LTG dose of 6.2 mg/kg/day (range 1.2-11) in the controlled group. Adverse events were present in three patients (15%); they were generally mild and transient. Our series confirms that LTG monotherapy may control typical childhood absence seizures in about half the children as well as it may decrease interictal generalized spike and wave discharges both in seizure-free and uncontrolled patients. The slow titration phase of the drug due to the risk of the skin rash may eventually reduce compliance.

Some antiepileptic compounds impair learning by rats in a Morris water maze

In the present experiments, we investigated the effects of several commonly employed antiepileptic drugs on the performance of adult rats in a Morris water maze task. We found that phenytoin treatment produced the most deleterious performance impairments across all days of training, and that these performance deficits are not likely due to any general sensorimotor impairments. Carbamazepine had milder, but detectable negative effects, as carbamazepine-treated animals exhibited initial acquisition deficits, but rapidly achieved escape levels comparable to controls. In marked contrast, valproate and ethosuximide had no detectable effects on learning in the water maze. These results parallel previous findings in rats treated with these compounds and tested in an instrumental learning task, and are in general agreement with the human clinical literature. To the extent that one might wish to minimize learning deficits associated with maintenance on antiepileptic drugs, phenytoin is definitely not the treatment of choice, while valproate or ethosuximide are apparently much less disruptive.

Comparison the cognitive effect of anti-epileptic drugs in seizure-free children with epilepsy before and after drug withdrawal

We studied the cognitive effects of antiepileptic drugs (AED), by investigating epileptic children who were seizure-free for at least 2 years and who had undergone fixed monotherapy. Seventy consecutive epileptic children (25 with carbamazepine (CBZ), 22 with phenobarbital (PB), and 23 with valproate (VPA)) were examined by Wechsler Intelligence Scale for Children-Revised (WISC-R) and auditory event-related potentials (P(300)) at three sessions: before AED reduction, then 1 and 7 months after complete withdrawal of treatment. There were no significant differences in IQ and subtests scores of WISC-R in any group at any of the three sessions. P(300) latencies were significantly increased in the children receiving PB but not in children receiving CBZ or VPA. P(300) amplitudes were increased but not significantly different among the three groups. These findings suggest that PB may affect cognitive function on children, but the changes of P(300) latencies may improve after discontinuation.

Converging evidence for the role of occipital regions in orthographic processing: a case of developmental surface dyslexia

Recently, there have been several reports focusing on the neural basis for word recognition. Two different views have emerged: one emphasizing the role of the left angular gyrus in recognizing printed words, and the second view suggesting that visual word processing activates the left extrastriate cortex. This paper describes the case of EBON, a 14-year-old girl with an extensive early (most likely congenital) brain lesion in the left occipital lobe. She demonstrates a clear pattern of developmental surface dyslexia in that she is more successful at reading and spelling regular words than irregular words and makes frequent regularization errors. Thus, EBON is the first case reported with the potential to establish converging evidence for the role of extrastriate regions in the left hemisphere in the acquisition of orthographic representations.

Does short-term antiepileptic drug treatment in children result in cognitive or behavioral changes?

PURPOSE

To determine possible cognitive and behavioral effects of antiepileptic drug (AED) therapy by assessing children with newly diagnosed epilepsy before and after initiation of treatment. A comparison group of children with diabetes mellitus (DM) was included to control for the effects of practice, maturation, and chronic illness.

METHODS

Baseline neuropsychological assessments were completed for children with epilepsy (n = 37) and children with DM (n = 26) recruited through outpatient clinics at a regional children's hospital. Children were reevaluated 6 months from baseline testing. At follow-up, children with epilepsy had therapeutic AED levels and controlled seizures. Statistical analysis included a between-group repeated measures ANCOVA with pretest scores serving as the covariate.

RESULTS

Significant differences between groups were not found for any cognitive or behavioral factors, including attention (p < 0.24), immediate memory (p < 0.24), delayed memory (p < 0.10), complex motor speed (p < 0.19), or behavior problems (p < 0.89).

CONCLUSIONS

Changes in performance on cognitive and behavioral measures were not different for children treated with AEDs and controls. Although adverse effects may be associated with prolonged treatment, results would not suggest adverse effects from AED monotherapy during the first 6 months of therapy.

Reversible cortical atrophy and cognitive decline induced by valproic acid

An 18-year-old male suffered from familial progressive myoclonic epilepsy from the age of 7 years. In addition to seizures, there was a marked decline in school performance. At the age of 14 years, sodium valproate was started as add-on therapy; 2 weeks later he was hospitalized in a stuporous state. The serum level of valproate was within the therapeutic range. Cognitive evaluation disclosed moderate mental retardation. No metabolic abnormalities were detected. Valproate was discontinued and during the 4 following months, a slow but significant improvement was documented in cognitive functions. Repeated assessment was within the range of mild mental retardation. Initially, magnetic resonance imaging (MRI) showed mild cortical atrophy. A subsequent MRI study performed 2 years later was normal.