There are two main causes of epilepsy: brain injuries and chemical or metabolic imbalances in the brain. Any brain injury may result in epilepsy, but in many cases there is no identifiable cause; when injury is the cause, there is a latent period before the onset of epilepsy. The physical events that cause epilepsy in early life include birth traumas, infections of the brain or meninges, and congenital abnormalities, while alcohol, drugs, tumours and cerebrovascular accidents tend to be the causes in later life.
Status Epilepticus occurs when a prolonged seizure or a series of seizures occurring in quick succession.
Low blood glucose, poor oxygenation of the blood and disturbances of blood electrolytes such as sodium or calcium ions also can precipitate seizures in patients who are susceptible; organ failure of the kidneys or liver may contribute to these changes. Genetic abnormalities may alter the excitability of neurones and predispose to the seizures.
Epilepsy is investigated by taking a full history of the seizures and performing EEGs to monitor electrical activity in the cortex, as well as MRI and other scans to establish the presence or absence of any injury or other pathology within the brain.
The temporal lobe is an area of the brain which in which an epileptic focus can produce symptoms associated with the function of structures in that lobe, such as the hippocampus and amygdala. These symptoms of Temporal Lobe Epilepsy include abnormal behaviour associated with the recall of memories, and fear or aggressive behaviour, and must be distinguished from other non-physical causes of these behaviours.
In epilepsy, the normal activity of cortical neurones is interrupted by wave patterns that indicate hyperexcitability of the tissues. These patterns occur in the absence of clinical signs (i.e. seizures), and their occurrence is reduced by antiepeileptic drugs, so EEG is useful not only in the diagnosis but in the monitoring of efficacy of drug treatment.
During the EEG test, patients are asked to overbreath because the alkalosis associated with overbreathing causes blood levels of ionised calcium to fall transiently, and early asymptomatic signs of epileptic activity may be observed in the electrical recordings.
It is known that some patients with epilepsy are susceptible to flashing lights and may be more likely to experience a fit in this situation. Because of this part of the investigation is to record and EEG while patients look at a flashing light; early asymptomatic electrical signs of an epileptic focus may be present during this investigation.
It is known that injury to the brain causes loss of pyramidal cells and other neurones as well as the formation of new synapses, and these processes are believed to play a part in the development of epileptic foci. GABAergic neurones within the cortex outnumber the pyramidal cells and have generalised inhibitory effects, and the loss of this type of neurone is associated with hyperexcitability of other cortical neurones.
Role of Glutamate receptors.