Epileptic seizures are sudden electrical discharges in specific brain regions or throughout the brain. Depending on the brain region where the discharge occurs, the seizures can take on very different forms. Therefore, two main types of epileptic seizures are distinguished: generalized and focal (also called partial seizures).
Generalized seizure
In a generalized seizure, the whole brain is affected by discharges of nerve cells right from the start, so there is automatically a loss of consciousness. As there are discharges in all the movement centres in the brain, there are also the familiar cramps and twitches all over the body. Cramping of the chewing muscles can cause tongue biting, so the saliva that comes out of the mouth may be bloodstained (foaming at the mouth). Due to cramping of the abdominal muscles, urination and defecation may occur because of the resulting pressure.
Partial (=focal) seizure
If, however, the discharges only take place at one location in the brain, which is called a focus, it is a focal seizure. A distinction is made here as to whether there is a sudden disturbance of consciousness/mental disturbance (complex focal) or not (simple focal). If the epileptic activity is limited to the movement centre in the brain that controls a hand, for example, all that happens is involuntary hand twitching with full consciousness (simple focal motor seizure). If the epileptic activity is restricted to the sensory centre of the hand, for example, there is a seizure-like disturbance of sensation in the hand (simple focal sensory seizure) with no other symptoms. If the epileptic activity is confined to the memory centre in the brain, there may be brief changes in consciousness (e.g., déjà vu , jamais vu experiences). These and focal sensory seizures are usually not noticed by outsiders. Sudden, short, vague feelings from the stomach area, a short seizure-like taste disturbance or optical illusions can also be indicative of a seizure focus in a very specific brain region.
Partial (=focal), secondary generalizing seizure
When there is a focal seizure, if the discharges subsequently spread throughout the entire brain, physicians refer to this as a secondary generalization of the seizure. About half of generalized seizures begin focally, but the focal onset is often not recognized. Sometimes patients report a forewarning of a generalized epileptic seizure (called an aura). This aura is already the partial (=focal) seizure (see above), which subsequently spreads to the whole brain.