The piriform, perirhinal, and entorhinal cortex in seizure generation

Abstract

Understanding neural network behavior is essential to shed light on epileptogenesis and seizure propagation. The interconnectivity and plasticity of mammalian limbic and neocortical brain regions provide the substrate for the hypersynchrony and hyperexcitability associated with seizure activity. Recurrent unprovoked seizures are the hallmark of epilepsy, and limbic epilepsy is the most common type of medically-intractable focal epilepsy in adolescents and adults that necessitates surgical evaluation. In this review, we describe the role and relationships among the piriform (PIRC), perirhinal (PRC), and entorhinal cortex (ERC) in seizure-generation and epilepsy. The inherent function, anatomy, and histological composition of these cortical regions are discussed. In addition, the neurotransmitters, intrinsic and extrinsic connections, and the interaction of these regions are described. Furthermore, we provide evidence based on clinical research and animal models that suggest that these cortical regions may act as key seizure-trigger zones and, even, epileptogenesis.

Epilepsy in multiple sclerosis: The role of temporal lobe damage

“…26 While it remains controversial whether the atrophy of temporal structures leads to epilepsy, or whether the recurrent seizures lead to cortical thinning, it is noteworthy that some patients suffering from temporal epilepsy have atrophic tissue exactly where the functional origin of the seizure is observed. 27 Altogether, these observations suggest that the atrophy of specific regions, for example, of the temporal lobe, might be essential to manifest a seizure, explaining why only a small part of MS patients with GMLs suffers from epilepsy. This was confirmed by the multivariate analysis of our study, showing that the number of GMLs in the hippocampus and the atrophy of temporal lobe (especially of the fusiform gyrus and of the inferior temporal gyrus) were independent predictors of the appearance of seizures.…”

Distinct mechanisms of Up state maintenance in the medial entorhinal cortex and neocortex

“…A relationship between seizure activity and Up state activity has been proposed (Žiburkus et al., 2013), and the entorhinal cortex is a prime focus for spontaneous epileptic activity (Vismer et al., 2015). Layer III pyramidal neurons of the mEC have been shown to degenerate selectively in kainate-induced animal models of epilepsy (Sperk et al., 1983), and in tissue samples from human patients extracted during surgical treatment of epilepsy (Du et al., 1993).…”

Effects of surgical targeting in laser interstitial thermal therapy for mesial temporal lobe epilepsy: A multicenter study of 234 patients

“…The rhinal cortices are known to be highly epileptogenic and intensely interconnected within the limbic network, 30 and Jermakowicz et al have previously described the importance of ablating the mesial hippocampal head. Further examination of the maps highlights the importance of targeting the mesial hippocampus, parahippocampal gyrus, entorhinal cortex, and perirhinal cortex-as missing these structures frequently resulted in persistent seizures.…”