Neuroscience of Epilepsy

Epilepsy is characterised by seizures, which are transient occurrences of abnormal neuronal activity in the brain. Seizures can be focal, affecting specific brain areas, or generalised, affecting both hemispheres. While the concept of ‘excitation/inhibition imbalance’ helps understand focal epilepsy, it is better understood as an ‘instability’ whereby local over-excitation is usually contained by inhibitory mechanisms, which can intermittently fail, leading to seizures. Absence seizures are generated by abnormal activity in a thalamocortical loop that normally subserves the generation of sleep rhythms, through a complex interplay between inhibition and excitation. This also involves specific ion channels governing neuronal excitability and rhythmogenesis. While any brain can have a seizure, epilepsy is characterised by changes in the brain that lead to an increased propensity to have seizures (this process is known as epileptogenesis). These changes can be driven by damage to the brain (e.g. following traumatic brain injury) or by intrinsic genetic abnormalities.