Neuronal chain stimulation during an epileptic attack.
By Eslam Abbas
Ictogenesis involves a characteristic transition from normal electrophysiological activity in the brain to abnormal hypersynchronization. In epilepsy, the resistance of excitatory neurons to fire is decreased. This may occur due to changes in ion channels, or inhibitory neurons not functioning properly (ISBN 978-0-07-162167-0). Yet, the mechanism by which these changes lead to hypersynchronous neuronal activity is unclear.
This idea describes briefly this mechanism depending on a concept of neuronal chain stimulation. Epilepsy-characteristic neural reorganization enhances neural connectivity in affected networks. Therefore, a chain stimulation reaction emerges automatically, under epileptogenic circumstances, when a critical number of hyperexcitable neurons involve in a focus.
• N < 1, subcriticality: no ictogenesis.
In manifest epilepsy, this case is maintained by using anti-epileptic drugs which generally increase the inhibitory pool in brain whilst, in acquired epilepsy, called a latent period.
• N = 1 or N > 1, criticality or supercriticality: variable degrees of epilepsy.
Neuronal chain interaction gives a network affected by reorganization, either genetically or acquired, the ability to stimulate a large number of neurons in no time taking advantage of the defect in the inhibitory pool. Therefore, the affected circuit roles a larger field as a pacemaker leading to hypersynchronous neuronal oscillations (seizure).