Changes of cortical epileptic afterdischarges after status epilepticus in immature rats

Epilepsy Research in the Institute of Physiology of the Czech Academy of Sciences in Prague

Starting from simple clinical statistics, the spectrum of methods used in epilepsy research in the Institute of Physiology of the Czechoslovak (now Czech) Academy of Sciences progressively increased. Professor Servít used electrophysiological methods for study of brain activity in lower vertebrates, neuropathology was focused on electronmicroscopic study of cortical epileptic focus and ion-sensitive microelectrodes were used for studies of cortical direct current potentials. Developmental studies used electrophysiological methods (activity and projection of cortical epileptic foci, EEG under the influence of convulsant drugs, hippocampal, thalamic and cortical electrical stimulation for induction of epileptic afterdischarges and postictal period). Extensive pharmacological studies used seizures elicited by convulsant drugs (at first pentylenetetrazol but also other GABA antagonists as well as agonists of glutamate receptors). Motor performance and behavior were also studied during brain maturation. The last but not least molecular biology was included into the spectrum of methods. Many original data were published making a background of position of our laboratory in the first line of laboratories interested in brain development.

Disparate properties of afterdischarges elicited by electric cortical stimulation in MRI lesional epilepsy patients with different surgical outcomes

PURPOSE

The purpose of this study was to demonstrate the prognostic value of afterdischarges(ADs) on surgical outcome by comparing the disparate properties in epilepsy patients with different surgical outcomes METHODS: 27 lesional epilepsy patients were retrospectively analyzed. The brain region covered by subdural electrodes in each patient was dichotomized into the area of the brain lobe(s) where the MRI lesion is located (region ML) and other brain areas (region nML). The occurrence of ADs and ADs evolving into clinical seizure, ADs threshold and ADs duration in region ML and nML were compared between seizure-free (SF) and non-seizure-free (nSF) patients.

RESULTS

A total of 2535 contacts were analyzed, and the total occurrence of ADs was 18.6% (471/2535). The overall occurrence of ADs in region ML (24.8%) was significantly higher than that in region nML (10.3%) (P < 0.001). In region ML, compared with SF patients, nSF patients had a lower occurrence of ADs (19.2% vs. 31.2%, P < 0.001), a higher occurrence of ADs evolves into clinical seizure (8.7% vs. 2.4%, P = 0.006), a higher ADs threshold (12.8 ± 4.1 mA vs. 11.0 ± 3.7 mA, P < 0.001) and a shorter ADs duration (15.3 ± 14.2 s vs. 20.6 ± 17.0 s, P < 0.001). However, in region nML, there was no significant difference in properties of ADs between SF and nSF patients.

CONCLUSION

Higher occurrence of ADs in region ML might predict a good outcome, whereas higher occurrence of ADs evolving into clinical seizure, higher ADs threshold and shorter ADs duration might predict an unfavorable surgical outcome. ADs might help predict surgical outcomes in epilepsy patients.

Which component of treatment is important for changes of cortical epileptic afterdischarges after status epilepticus in immature rats?

Role of lithium chloride and paraldehyde in acute changes after lithium-pilocarpine status epilepticus (SE) induced at postnatal day 12 was studied in 15-day-old rats. In addition to SE group four other groups were formed: naïve animals without any injection, lithium chloride group, paraldehyde group and lithium-paraldehyde group. Cortical epileptic afterdischarges (CxADs) induced by increasing intensities of stimulation current were used as a measure of excitability. SE animals did not exhibit any change in duration of CxADs with increasing stimulation intensity in contrast to naïve control with a progressive prolongation of CxAD. LiCl group was similar to SE rats whereas paraldehyde and lithium-paraldehyde groups exhibited some progress in duration of ADs. Lithium chloride participates in short-term changes of CxADs after SE. Paraldehyde and combination of lithium and paraldehyde are similar to naïve controls.

New insight on the mechanisms of epileptogenesis in the developing brain

The incidence of epilepsy is at its highest in childhood and seizures can persist for a lifetime. As brain tissue from pediatric patients with epilepsy is rarely available, the analysis of molecular and cellular changes during epileptogenesis, which could serve as targets for treatment approaches, has to rely largely on the analysis of tissue from animal models. However, these data have to be analyzed in the context of the developmental stage when the insult occurs. Here we review the current status of the available animal models, the molecular analysis done in these models, as well as treatment attempts to prevent epileptogenesis in the immature brain. Considering that epilepsy is one of the major childhood neurological diseases, it is remarkable how little is known on epileptogenesis in the immature brain at a molecular level. It is a true challenge for the future to expand the armamentarium of clinically relevant animal models, and systematic analysis of molecular and cellular data to enhance the probability of developing syndrome specific antiepileptogenic treatments and biomarkers for acquired pediatric epileptogenesis.