Absences in adult seizure disorders

Praxis induction and its relationship with cognition in genetic generalized epilepsy

INTRODUCTION

Praxis induction (PI) is a reflex trait defined as the precipitation of epileptic discharges (ED) or seizures by cognition-guided tasks that often involve visuomotor coordination and decision-making. This is a characteristic of genetic generalized epilepsy (GGE), and especially of juvenile myoclonic epilepsy (JME). Additionally, several studies have described dysexecutive traits in these patients. Our objective was to analyze PI in the different syndromes of GGE and explore the relationship between PI and cognitive performance.

METHODS

Sixty-one adult patients with GGE underwent video-electroencephalograph (EEG) during which a neuropsychological activation protocol (NPAP) was performed: reading, writing, calculations, crosswords, and tangram. Praxis induction was defined by the presence of ED during the NPAP with a persistence of at least twice seen on the basal EEG. All patients also underwent a comprehensive cognitive evaluation.

RESULTS

We observed PI in 22 out of 61 patients (36%). Grouped by syndrome, PI was more frequent in adult patients with persistent childhood or juvenile absence epilepsy (JAE, 60%), followed by JME (42.1%) and in a lesser grade in patients with only tonic-clonic generalized seizures (9%). Patients classified as having PI did not obtain worse results in the cognitive evaluation. The presence of ED during the performance of a test was associated with a trend to lower results in that specific test.

SIGNIFICANCE

Our study showed a relevant presence of PI in patients whose absence epilepsy persists into adulthood, and not only in JME, the syndrome classically associated with PI. According to our results, PI as a reflex trait does not imply necessarily a poorer cognitive phenotype, but the induction of frequent ED during the tasks could be associated with transient cognitive impairment.

Clinical and electroencephalographic characteristics of a cohort of patients with epilepsy and absence seizures

BACKGROUND

Epileptic syndromes with absence seizures (AS) possess unique clinical and electroencephalographic (EEG) characteristics. In typical or atypical AS, ictal phenomenology may include various characteristics. Vídeo-EEG monitoring enables findings to be correlated with ictal phenomenology.

OBJECTIVE

To evaluate the different AS in a cohort of patients with drug-resistant epilepsy (DRE) based on the International League against Epilepsy (ILAE)'s 2006 classification, to correlate with ictal phenomenology recorded and to apply the Panayiotopoulos criteria.

METHOD

This study included patients with criteria of AS followed up at the Epilepsy Clinic. A dual, cross-sectional cohort study was carried out between 2005 and 2008. Patients receiving care in the Epilepsy Program of the HUCFF-UFRJ, who had been investigated by video-EEG and who presented clinical and EEG criteria for absence seizures, typical or atypical, according to the criteria defined by the ILAE, were included in the study, independent of age onset, the review of clinical history, age onset, family history, epilepsy onset and evolution, seizures phenomenology, antiepileptic drugs response and neuroimaging studies were used to classify the patients among the different epileptic syndrome associated to absence seizures.

RESULTS

Typical absences were more frequent (71.4%) than atypical absences. Cases of juvenile absence epilepsy were the most frequent (19%) in this series, followed by childhood absence epilepsy (14.4%) and juvenile myoclonic epilepsy (4.8%). In 14 patients (66.67%), diagnosis was modified from focal epilepsy to primary generalized epilepsy. Clinical and EEG diagnosis of absence epilepsy resulted in a dramatic improvement in the control of seizures following modification of diagnosis and indication of an appropriate antiepileptic drug.

CONCLUSION

Our results show that typical AS are more frequent than atypical. AS was successfully defined in 10 patients following application of Panayiotopoulos' criteria. The consequent change in diagnosis and therapy resulted in resolution of refractoriness in 9 patients. We concluded that in DRE, AS associated to unusual ictal phenomenology improve dramatically when diagnosed by video-EEG, permitting seizures to be controlled. Clinical and EEG evaluation confirm that myoclonus, automatisms and autonomic disorders are involved and that the consciousness may be affected to different degrees.

Absence seizures: a review of recent reports with new concepts

Absence seizures with bilateral spike-wave (SW) complexes at 3Hz are divided into the childhood form, with onset at around 6 years of age, and the juvenile form, with onset usually at 12 years of age. These seizures typically last 9-12s and, at times, are activated by hyperventilation and occasionally by photic stimulation. Generalized tonic-clonic (GTC) seizures may also occur, especially in the juvenile form. There may be cognitive changes, in addition to linguistic and behavioral problems. Possible mechanisms for epileptogenesis may involve GABAergic systems, but especially T-calcium channels. The thalamus, especially the reticular nucleus, plays a major role, as does the frontal cortex, mainly the dorsolateral and orbital frontal areas, to the extent that some investigators have concluded that absence seizures are not truly generalized, but rather have selective cortical networks, mainly ventromesial frontal areas and the somatosensory cortex. The latter network is a departure from the more popular concept of a generalized epilepsy. Between the "centrencephalic" and "corticoreticular" theories, a "unified" theory is presented. Proposed genes include T-calcium channel gene CACNA1H, likely a susceptible gene in the Chinese Han population and a contributory gene in Caucasians. Electroencephalography has revealed an interictal increase in prefrontal activity, essential for the buildup of the ictal SW complexes maximal in that region. Infraslow activity can also be seen during ictal SW complexes. For treatment, counter to common belief, ethosuximide may not increase GTC seizures, as it reduces low-threshold T-calcium currents in thalamic neurons. Valproic acid and lamotrigine are also first-line medications. In addition, zonisamide and levetiracetam can be very helpful in absence epilepsy.

Onset of polyspike complexes in a mean-field model of human electroencephalography and its application to absence epilepsy

In this paper, we introduce a modification of a mean-field model used to describe the brain's electrical activity as recorded via electroencephalography (EEG). The focus of the present study is to understand the mechanisms giving rise to the dynamics observed during absence epilepsy, one of the classical generalized syndromes. A systematic study of the data from a number of different subjects with absence epilepsy demonstrates a wide variety of dynamical phenomena in the recorded EEG. In addition to the classical spike and wave activity, there may be polyspike and wave, wave spike or even no discernible spike-wave onset during seizure events. The model we introduce is able to capture all of these different phenomena and we describe the bifurcations giving rise to these different types of seizure activity. We argue that such a model may provide a useful clinical tool for classifying different subclasses of absence epilepsy.