Cortical triggers in generalized reflex seizures and epilepsies

Abstract

Activation of specific cortical territories by sensory stimuli or of less restricted areas of the brain by cognitive stimuli is known to induce apparently generalized seizures in predisposed patients; this is clinically and electroencephalographically distinct from reflex triggering of partial seizures. Photosensitive patients may have seizures when exposed to environmental stimuli producing appropriate flickering light or geometric patterns. Some children with benign myoclonic epilepsy in infancy have seizures triggered by unexpected touch or noise. Seizures induced by thinking have been reported in response to non-verbal higher mental activity such as mental arithmetic. Praxis-induced seizures are triggered by similar mental activities accompanied by the use of the hands. Language-induced seizures are usually triggered by verbal higher mental activity. Functional imaging and other methods have contributed to understanding how these seizures arise. Patients with these generalized reflex seizures appear to have regions of cortical hyperexcitability overlapping or coinciding with areas physiologically activated during specific sensory stimulations and cognitive or motor activities. When these areas receive appropriate afferent volleys and a critical mass of cortex is activated, an epileptic activity is produced that ultimately involves cortico-reticular or cortico-cortical pathways resulting in a generalized or bilateral epileptic event.

The Effect of Cognitive Functions on EEG in Patients with Juvenile Myoclonic Epilepsy

“…[1][2][3][4] The relation between spontaneous epileptiform activity and cognitive functions has been studied with an increasing interest since present. [7][8][9][10][11][12][13][14] Seizures induced by higher mental activities have encouraged studies which were designed with special EEG activation methods to show any effect of mental tasks on the EEG of epileptic patients. [11][12][13][14] Matsuoka et al [11] used a neuropsychological method testing for various mental activities as a part of routine EEG examination for patients with epilepsy.…”

“…[1][2][3][4] It has been also demonstrated that spesific or nonspecific complex cognitive activities such as calculations, constructive activities, drawing, playing strategic board games are able to precipitate seizures. [7][8][9][10][11][12][13][14][15] In the treatment of JME not only antiepileptic drug therapy but also identification and regulation of seizure precipitant factors are important.…”

Startle Epilepsy

“…Refleks epilepsilerin oluşum mekanizması halen net anlaşılama-mıştır.Ancak nöbeti tetikleyen uyarana karşı beyin kortkesinin aşırı duyarlı olduğu düşünülmektedir (8). Chauvel ve ark.…”

Abnormal Brain Network in Epilepsy and Associated Comorbidites

“…Long-range connections were increased during SWD, particularly between frontal and posterior brain regions. In a fMRI study involving a working memory paradigm [50], the researchers found increased functional connectivity between the motor system and areas of higher cognitive functions within the frontal and the parietal lobes, which might explained clinical feature that myoclonic jerks could be triggered by cognitive effort in some patients with JME [51]. Additionally, in patients under valproic acid (VPA) treatment, abnormal motor cortex co-activation was negatively associated with an increasing daily VPA dose, which might underlie the beneficial effect of VPA on controlling myoclonic jerks [50].…”