Antiepileptic Drugs and the Significance of Event-Related Potentials

Neurophysiological and neuropsychological parameters in patients with temporal lobe epilepsy

Temporal lobe epilepsy (TLE) is the most common type of localization-related epilepsy (LRE) and has been extensively studied in the field of neuropsychology due to its significant association with cognitive impairments. Cognitive decline has long been recognized as a consequence of this form of epilepsy, with previous studies primarily focusing on neurophysiological measures. In this study, both neurophysiological and neuropsychological factors were analyzed in TLE patients compared to healthy control subjects. The Montreal Cognitive Assessment (MoCA) and Mini Mental State Examination (MMSE) tests were used to assess neuropsychological processes, while cognitive event-related potential (ERPs), particularly P300, were employed to analyze neurophysiological parameters. The study involved 21 TLE patients (mean age = 61.43) and 21 healthy control subjects. The results revealing that TLE patients scored significantly lower, indicating deficits in specific cognitive areas. The study also observed abnormalities in the ERPs, particularly in the assessment of P300 amplitude and latency, that may be indicative of underlying neural dysfunction related to attention and cognitive processing. In conclusion, the study provides compelling evidence of the association between TLE and a high incidence of cognitive deficits and decline. By considering both neurophysiological and neuropsychological factors, the study sheds light on the comprehensive impact of TLE on various cognitive domains and emphasizes the importance of early identification and management of cognitive impairments in TLE patients.

Prenatal exposure to antiepileptic drugs and early processing of emotionally relevant sounds

INTRODUCTION

Prenatal exposure to antiepileptic drugs (AEDs) is associated with developmental compromises in verbal intelligence and social skills in childhood. Our aim was to evaluate whether a multifeature Mismatch Negativity (MMN) paradigm assessing semantic and emotional components of linguistic and emotional processing would be useful to detect possible alterations in early auditory processing of newborns with prenatal AED exposure.

MATERIAL AND METHODS

Data on AED exposure, pregnancy outcome, neuropsychological evaluation of the mothers, information on maternal epilepsy type, and a structured neurological examination of the newborn were collected prospectively. Blinded to AED exposure, we compared a cohort of 36 AED-exposed with 46 control newborns at the age of two weeks by measuring MMN with a multifeature paradigm with six linguistically relevant deviant sounds and three emotionally uttered sounds.

RESULTS

Frontal responses for the emotionally uttered stimulus Happy differed significantly in the exposed newborns compared with the control newborns. In addition, responses to sounds with or without emotional component differed in newborns exposed to multiple AEDs compared with control newborns or to newborns exposed to only one AED.

CONCLUSIONS

These preliminary findings suggest that prenatal AED exposure may alter early processing of emotionally and linguistically relevant sound information.

Cognitive impairment in generalized anxiety disorder revealed by event-related potential N270

BACKGROUND

Cognitive function in anxiety disorders has been the subject of limited investigation, especially in generalized anxiety disorder (GAD). The purpose of this study was to investigate the cognitive function in subjects with GAD using mismatch-triggered negativity N270.

METHODS

Fifteen medication-free patients with a DSM-IV diagnosis of GAD, and 15 well-matched healthy controls performed a dual-feature delayed matching task while event-related potentials were recorded from their scalp.

RESULTS

The GAD group was characterized by the decreased N270 amplitude in the left hemisphere. The smaller N270 amplitude was associated with greater symptoms of anxiety and depression.

CONCLUSION

Since N270 is thought to index cognitive function in different domains, including attention and memory, our results suggest that individuals with GAD have an impaired cognitive function, particularly in selective attention and working memory. These cognitive deficits may have clinical significance in subjects with GAD and should be considered in treatment planning.

Aroma helps to preserve information processing resources of the brain in healthy subjects but not in temporal lobe epilepsy

PURPOSE

Inhalation of ylang-ylang aroma has been shown to reduce the auditory P300, an event-related potential thought to reflect higher-order processing. Because olfactory function is sometimes disturbed in temporal lobe epilepsy (TLE), the objective of the present study was to determine whether the effect of ylang-ylang aroma on the auditory P300 was impaired in patients with TLE.

METHOD

Fourteen subjects with TLE and 14 healthy controls participated in this study. Electroencephalograms were recorded during an auditory oddball task, and ylang-ylang aroma or odorless air was delivered through a mask.

RESULTS

We found that the ylang-ylang aroma prolonged the latencies of P300 in both groups. The ylang-ylang aroma significantly reduced the P300 amplitudes of healthy subjects as described previously. However, in TLE patients, the P300 was unaffected by the aroma.

CONCLUSION

The current results show that exposure to the ylang-ylang aroma reduced information processing resources in healthy subjects but had limited effects in patients with TLE. We suggest that impaired higher-order olfactory processing in TLE patients may inhibit the effects of the ylang-ylang aroma on the P300.

Remote effects of hippocampal sclerosis on effective connectivity during working memory encoding: a case of connectional diaschisis?

Accumulating evidence suggests a role for the medial temporal lobe (MTL) in working memory (WM). However, little is known concerning its functional interactions with other cortical regions in the distributed neural network subserving WM. To reveal these, we availed of subjects with MTL damage and characterized changes in effective connectivity while subjects engaged in WM task. Specifically, we compared dynamic causal models, extracted from magnetoencephalographic recordings during verbal WM encoding, in temporal lobe epilepsy patients (with left hippocampal sclerosis) and controls. Bayesian model comparison indicated that the best model (across subjects) evidenced bilateral, forward, and backward connections, coupling inferior temporal cortex (ITC), inferior frontal cortex (IFC), and MTL. MTL damage weakened backward connections from left MTL to left ITC, a decrease accompanied by strengthening of (bidirectional) connections between IFC and MTL in the contralesional hemisphere. These findings provide novel evidence concerning functional interactions between nodes of this fundamental cognitive network and sheds light on how these interactions are modified as a result of focal damage to MTL. The findings highlight that a reduced (top-down) influence of the MTL on ipsilateral language regions is accompanied by enhanced reciprocal coupling in the undamaged hemisphere providing a first demonstration of "connectional diaschisis."

Cognitive effects of topiramate revealed by standardised low-resolution brain electromagnetic tomography (sLORETA) of event-related potentials

OBJECTIVE

To evaluate the effect of topiramate (TPM) on event-related potentials (ERPs) in patients with epilepsy.

METHODS

Neuropsychological tests and ERP study using auditory oddball paradigm were conducted before and after treatment with TPM in drug-naive epilepsy patients. To detect target brain regions in which ERP changed during the cognitive task, cortical current densities of ERP components were analysed using standardised low-resolution electromagnetic tomography (sLORETA).

RESULTS

Neuropsychological tests (n=18 patients) showed that TPM significantly decreased the score in digit span, Corsi block and Controlled Oral Word Association word fluency. Repeated-measures analysis of variance of ERP data (n=13 patients) revealed that P2 amplitude was significantly increased at Fz electrode following treatment with TPM. Statistical non-parametric map of sLORETA between pre- and post-TPM ERPs revealed that current density of P200 component was significantly reduced by TPM in bilateral parieto-occipital, temporolimbic and dorsolateral right prefrontal regions.

CONCLUSIONS

Our findings suggest that TPM affects selective brain regions which may be related to cognitive side effects.

SIGNIFICANCE

Source localisation of ERPs can be helpful in identifying target brain regions for the cognitive side effects of anti-epileptic drugs.

Electrophysiological and auditory behavioral evaluation of individuals with left temporal lobe epilepsy

The purpose of this study was to determine the repercussions of left temporal lobe epilepsy (TLE) for subjects with left mesial temporal sclerosis (LMTS) in relation to the behavioral test-Dichotic Digits Test (DDT), event-related potential (P300), and to compare the two temporal lobes in terms of P300 latency and amplitude. We studied 12 subjects with LMTS and 12 control subjects without LMTS. Relationships between P300 latency and P300 amplitude at sites C3A1,C3A2,C4A1, and C4A2, together with DDT results, were studied in inter-and intra-group analyses. On the DDT, subjects with LMTS performed poorly in comparison to controls. This difference was statistically significant for both ears. The P300 was absent in 6 individuals with LMTS. Regarding P300 latency and amplitude, as a group, LMTS subjects presented trend toward greater P300 latency and lower P300 amplitude at all positions in relation to controls, difference being statistically significant for C3A1 and C4A2. However, it was not possible to determine laterality effect of P300 between affected and unaffected hemispheres.

Divalproex sodium in children with partial seizures: 12-month safety study

This phase III, open-label, multicenter, outpatient study evaluated the 12-month safety of valproate using divalproex sodium sprinkle capsules for partial seizures, with or without secondary generalization, in children aged 3-10 years (n = 169). Laboratory parameters and vital signs were assessed, and the Wechsler Scales of Intelligence, the Developmental Profile-II, movement-related items from the Udvalg for Kliniske Undersøgelser, and the Behavior Assessment System for Children were administered. Efficacy was measured by the 4-week seizure rate. The most common treatment-emergent adverse events in the 169 study patients were typical childhood illnesses: pyrexia (18%), cough (17%), and nasopharyngitis (14%). The most common adverse events not considered typical childhood illnesses were vomiting (14%), tremor (9%), somnolence (8%), and diarrhea (8%). Of the 169 patients, 11 (6.5%) were hospitalized with serious treatment-emergent adverse events. Although elevated ammonia levels were observed in 31 treated patients, and mean increases in uric acid concentrations and decreases in platelets were observed, the majority of patients were asymptomatic. Except for tremor, no increases in movement-related adverse effects were observed. Small numeric improvements were reported in the Wechsler Scales and the Behavior Assessment System for Children. The safety findings in this 12-month study are generally consistent with previous reports of valproate in adult and pediatric epilepsy patients.

Attention changes in epilepsy patients following 3-month topiramate or valproate treatment revealed by event-related potential

The present study was designed to reveal changes of cognitive processes in epilepsy (EP) patients with Topiramate (TPM) or Valproate (VPA) treatment using Wechsler Adult Intelligence Scale (WAIS-CR) and event-related potential (ERP). Thirty untreated epilepsy patients were randomly divided into two groups receiving TPM or VPA, respectively. Fifteen healthy volunteers were included as controls. All the patients were examined by WAIS-CR and ERP before and 3 months after drug treatment. Controls were examined by ERP at the time recruited into the study and 3 months later. Unfamiliar grey-scale photographs of faces (front view) were used as stimuli. ERP were recorded at the same time. Mean Intelligence Quotient (IQ) in TPM group decreased after the 3-month treatment (90.40 vs. 81.00, P<0.05). One component of ERP-P300 was smaller in epilepsy patients than controls (P<0.05), but remained unchanged after TPM or VPA treatment (P>0.05). A delayed and smaller N270 was detected in patients compared to controls (P<0.05). After 3 months TPM treatment, it decreased further compared to before treatment (P<0.05). N170 was lower in patient groups, and it became lower after TPM treatment than before. Our results demonstrate that in all epilepsy patients with mild cognitive impairment ERP changes were found. TPM affected the cognitive functions in epilepsy patients reflected by the decreased full-scale intelligence quotient (FIQ). The imperative effects of TPM on visual perception function reflected by N170 were more obvious than that of VPA. Attention reflected by N270 was impaired after TPM treatment.