Epileptogenesis

Epileptogenesis is the gradual process by which a normal brain develops epilepsy. Epilepsy is a chronic condition in which seizures occur. These changes to the brain occasionally cause neurons to fire in a hyper-synchronous manner. This hyper-synchronous firing of neurons is called a seizure.

The causes of epilepsy are broadly classified as being genetic, structural/metabolic, or unknown. Anything that causes epilepsy causes epileptogensis, because epileptogenesis is the process of developing epilepsy. Structural causes of epilepsy include neurodegenerative diseases, traumatic brain injury, stroke, brain tumor, infections of the central nervous system, and status epilepticus (a prolonged seizure or a series of seizures occurring in quick succession).

After a brain injury occurs, there is frequently a "silent" or "latent period" lasting months or years in which seizures do not occur; Canadian neurosurgeon Wilder Penfield called this time between injury and seizure "a silent period of strange ripening". During this latent period, changes occur in the structure and physiology of the brain that result in the development of epilepsy. It is this process in which hyperexcitable neural networks form that is referred to as epileptogenesis, and it is during this latent period that symptoms of epilepsy first occur. If researchers come to better understand epileptogenesis, the latent period may provide a chance for healthcare providers to interfere with the development of epilepsy or reduce its severity.

Changes that occur during epileptogenesis are poorly understood but are thought to include cell death, axonal sprouting, reorganization of neural networks, alterations in the release of neurotransmitters, and neurogenesis. These changes cause neurons to become hyperexcitable and can lead to spontaneous seizures.

Brain regions that are highly sensitive to insults and can cause epileptogenesis include temporal lobe structures such as the hippocampus, the amygdala, and the piriform cortex.

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