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Epilepsy: Ever-changing states of cortical excitability.

Summary of "Epilepsy: Ever-changing states of cortical excitability."

It has been proposed that the underlying epileptic process is mediated by changes in both excitatory and inhibitory circuits leading to the formation of hyper-excitable seizure networks. In this review we aim to shed light on the many physiological factors that modulate excitability within these networks. These factors have been discussed extensively in many reviews each as a separate entity and cannot be extensively covered in a single manuscript. Thus for the purpose of this work in which we aim to bring those factors together to explain how they interact with epilepsy, we only provide brief descriptions. We present reported evidence supporting the existence of the epileptic brain in several states; interictal, peri-ictal and ictal, each with distinct excitability features. We then provide an overview of how many physiological factors influence the excitatory/inhibitory balance within the interictal state, where the networks are presumed to be functioning normally. We conclude that these changes result in constantly changing states of cortical excitability in patients with epilepsy.

Affiliation

Department of Clinical Neurosciences, St Vincent's Hospital, Fitzroy, Australia; Department of Medicine, The University of Melbourne, Parkville, Australia; Department of Electrical and Electronic Engineering, The University of Melbourne, Parkville, Austra

Journal Details

This article was published in the following journal.

Name: Neuroscience
ISSN: 1873-7544
Pages: 89-99

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Medical and Biotech [MESH] Definitions

A neurosurgical procedure that removes or disconnects the epileptogenic CEREBRAL CORTEX of a hemisphere. Hemispherectomy is usually performed for patients with intractable unilateral EPILEPSY due to malformations of cortical development or brain lesions. Depending on the epileptogenic area in the hemisphere, cortical removal can be total or partial.

A disorder characterized by recurrent partial seizures marked by impairment of cognition. During the seizure the individual may experience a wide variety of psychic phenomenon including formed hallucinations, illusions, deja vu, intense emotional feelings, confusion, and spatial disorientation. Focal motor activity, sensory alterations and AUTOMATISM may also occur. Complex partial seizures often originate from foci in one or both temporal lobes. The etiology may be idiopathic (cryptogenic partial complex epilepsy) or occur as a secondary manifestation of a focal cortical lesion (symptomatic partial complex epilepsy). (From Adams et al., Principles of Neurology, 6th ed, pp317-8)

A localization-related (focal) form of epilepsy characterized by recurrent seizures that arise from foci within the temporal lobe, most commonly from its mesial aspect. A wide variety of psychic phenomena may be associated, including illusions, hallucinations, dyscognitive states, and affective experiences. The majority of complex partial seizures (see EPILEPSY, COMPLEX PARTIAL) originate from the temporal lobes. Temporal lobe seizures may be classified by etiology as cryptogenic, familial, or symptomatic (i.e., related to an identified disease process or lesion). (From Adams et al., Principles of Neurology, 6th ed, p321)

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