Even in poorly controlled epilepsy, studies over 20 years have shown no substantial cognitive decline. Seizures and drugs can affect memory and concentration, but such effects are reversible. Even after the removal of brain cells through surgery, we sometimes find that memory improves because of the decrease in seizures. Brain cell loss and seizures on their own do not cause dementia. Blood pressure drops during a seizure, usually returning to normal with no resulting problems in convulsions lasting less than five minutes, but if the seizure is prolonged and blood pressure remains low for longer, insufficient blood will reach the brain.
Blood transports both oxygen and glucose, which is the food for cells.
When seizures are prolonged, the brain will eventually be deprived of oxygen and the nerve cells start dying. Additionally a convulsion uses up glucose and if insufficient blood reaches the brain to provide sufficient glucose, this too can cause nerve cell damage. The realisation that prolonged seizures can damage the brain is not new. It was noted as far back as 1825 that long seizures seemed to cause damage to the hippocampus, the part of the brain important for the formation of memory. Importantly, just over 100 years ago, it was also noted that people with an already damaged hippocampus would or could develop epilepsy.