Exposure to Exogenous Factors

Epilepsy is a disease that develops on the basis of a genetically determined predisposition, for the manifestation of which, in most cases, exogenous factors determining its clinical manifestation are necessary.

One of the main genetically determined factors in the development of epilepsy is the synchronization of the activity of neurons in all frequency ranges. Pathognomonic feature of epileptic neurons is a paroxysmal depolarization shift of their membrane potential. The paroxysmal depolarization shift leads to the fact that the neuron generates an action potential of much greater amplitude, duration, and frequency than normal. Without this, further stages of epileptogenesis are impossible.
A contributing factor to the onset of seizures is the presence of organic abnormalities in the brain.

The cause of structural disorders underlying the formation of epileptic foci are pre-, peri- and postnatal effects on cortical neurons. The most significant in the process of cortical dysgenesis is a violation of the migration of neurons, the delay and defects in their differentiation. As a result, disturbances in the migration of neurons can develop heterotopies, agenesis and other defects, which are the structural basis of epilepsy in the future.

Postnatal damage includes trauma, hypoxia, ischemia, inflammation, mass lesions, etc., which leads to the appearance of symptomatic epilepsy. The primary focus of epileptic activity is a neural network in the area surrounding the destruction. The epileptogenic focus has been shown to include several functional zones (Lurdes et al., 1993): epileptogenic damage, primary epileptogenic zone, symptomatic zone, functional deficit zone, irritative zone. Epileptogenic damage corresponds to the zone of structural brain damage (cyst, focal cortical dysplasia, etc.). This damage can be detected by MRI. The primary epileptogenic zone is an area of ​​the cortex capable of generating epileptic discharges. Surgical removal of the primary epileptogenic zone can lead to relief of epileptic paroxysms (Lurdes, 1993). Localization of the primary epileptogenic zone is established on the basis of EEG studies at the time of the attack using deep-seated electrodes.

Symptomatogenous zone – the area of ​​the cortex, upon activation of which the initial clinical symptoms of epileptic paroxysm develop. The functional deficit zone is the area of ​​the cortex, the functional changes in the neurons of which lead to the occurrence of neurological and neuropsychological disorders.

The localization of the functional deficit zone is determined on the basis of neurological and neuropsychological examinations, as well as such neuroradiological research methods, such as PET and SPECT (Wieser et al., 1995). Irritative zone – a region of the cortex in which epileptic activity is recorded (peaks, sharp waves, etc.) in the interictal period.

local_offerevent_note February 9, 2019

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