Regional accumulation of 14C-zonisamide in rat brain during kainic acid-induced limbic seizures

The Effect of Anti-seizure Medications on the Propagation of Epileptic Activity: A Review

The propagation of epileptiform events is a highly interesting phenomenon from the pathophysiological point of view, as it involves several mechanisms of recruitment of neural networks. Extensive in vivo and in vitro research has been performed, suggesting that multiple networks as well as cellular candidate mechanisms govern this process, including the co-existence of wave propagation, coupled oscillator dynamics, and more. The clinical importance of seizure propagation stems mainly from the fact that the epileptic manifestations cannot be attributed solely to the activity in the seizure focus itself, but rather to the propagation of epileptic activity to other brain structures. Propagation, especially when causing secondary generalizations, poses a risk to patients due to recurrent falls, traumatic injuries, and poor neurological outcome. Anti-seizure medications (ASMs) affect propagation in diverse ways and with different potencies. Importantly, for drug-resistant patients, targeting seizure propagation may improve the quality of life even without a major reduction in simple focal events. Motivated by the extensive impact of this phenomenon, we sought to review the literature regarding the propagation of epileptic activity and specifically the effect of commonly used ASMs on it. Based on this body of knowledge, we propose a novel classification of ASMs into three main categories: major, minor, and intermediate efficacy in reducing the propagation of epileptiform activity.

Zonisamide changes unilateral cortical excitability in focal epilepsy patients

Background and Purpose

To evaluate changes in cortical excitability induced by zonisamide (ZNS) in focal epilepsy patients.

Methods

Twenty-four drug-naїve focal epilepsy patients (15 males; overall mean age 29.8 years) were enrolled. The transcranial magnetic stimulation parameters obtained using two Magstim 200 stimulators were the resting motor threshold, amplitude of the motor-evoked potential (MEP), cortical silent period, short intracortical inhibition, and intracortical facilitation. These five transcranial magnetic stimulation parameters were measured before and after ZNS, and the findings were compared.

Results

All 24 patients were treated with ZNS monotherapy (200-300 mg/day) for 8-12 weeks. After ZNS, MEP amplitudes decreased (-36.9%) significantly in epileptic hemispheres (paired t-test with Bonferroni's correction for multiple comparisons, p<0.05), whereas the mean resting motor threshold, cortical silent period, short intracortical inhibition, and intracortical facilitation were unchanged (p>0.05). ZNS did not affect cortical excitability in nonepileptic hemispheres.

Conclusions

These findings suggest that ZNS decreases cortical excitability only in the epileptic hemispheres of focal epilepsy patients. MEP amplitudes may be useful for evaluating ZNS-induced changes in cortical excitability.

Mechanisms of status epilepticus: an evidence-based review

(1) Status epilepticus is a significant health problem that is under-recognized, yet is associated with major morbidity and mortality. (2) Mechanisms accounting for status epilepticus emergence from a single seizure, and for prolonged status epilepticus duration, remain unclear. (3) No randomized controlled trials, systematic reviews, or meta-analyses were found in any of the databases searched regarding the pathophysiologic mechanisms of status epilepticus in humans. (4) Ongoing and future research is likely to more clearly define the pathogenetic mechanisms of status epilepticus. This, in turn, is likely to encourage better treatment 'targeting' for particular aspects of the condition.

Differences in two mice strains on kainic acid-induced amygdalar seizures

Seizure susceptibility and neurodegeneration induced by microinjection of kainic acid (KA) into the left amygdala (LA) in C57BL/6 and FVB/N mouse strains were compared. Mice were administered 0.5 microg of KA into the LA. Electroencephalograms (EEGs) and behavior were monitored for 48 h after KA microinjection. Neuronal cell damages in the CA1 and CA3 regions of hippocampus were assessed at 2 and 48 h after KA microinjection. We demonstrated that the FVB/N mice showed longer duration of seizure activity than the C57BL/6 mice in EEGs and behavioral observation. The C57BL/6 mice were resistant to neurodegeneration while the FVB/N mice were vulnerable as measured 2 and 48 h after KA microinjection. These differences might be associated with genetic background.