Seizures and Epilepsy
Epileptic seizure: synchronous excessive discharge of neurons in the cerebral cortex, manifesting as a stereotyped disturbance of consciousness, behavior, emotion, motor function, or sensation.
Classically with sudden onset, lasting seconds to minutes, and usually ceases spontaneously.
Epilepsy: Chronic tendency for recurrent spontaneous unprovoked seizure.
Status epileptics A medical emergency with a high mortality rate caused by the state of continuous or recurrent seizures, with failure to regain consciousness between seizures over 30 minutes.
Can cause anoxic brain damage.
Prodrome: Premonitory changes in mood or behavior; these may precede the attack by some hours.
Ictus: The attack or seizure itself.
Postictal period: The time after the ictus during which the patient may be drowsy, confused and disorientated.
May have focal neurological signs (e.g. Todd’s paralysis).
1. Mechanism of seizure initiation and propagation
Long-lasting depolarization of the neuronal membrane due to influx of extracellular (Ca2+)!opening of voltage-dependent sodium (Na+) channels!influx of Na+, and generation of repetitive action potentials!hyperpolarizing mediated by GABA receptors or potassium (K+) channels.
b. Propagation (the process by which a partial seizure spreads):
Sufficient activation to recruit neurons!loss of nearby inhibition!spread of seizure activity.
a. Transformation of a normal neuronal network into a chronically hyperexcitable one.
Initial CNS injury (trauma, stroke, or infection) ! months/years! first seizure.
Injury starts a process that progressively lowers the seizure threshold in the affected region ! spontaneous seizure occurs.
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Written by: Abdullah AlAsaad
Reviewed by: Roaa Amer
Haifa Al Issa
Web Publisher: Adel Yasky