An epileptic seizure is caused by excessive and/or hyper synchronous electrical neuronal activity, and is usually self-limiting. It can manifest as an alteration in mental state, tonic or clonic movements, convulsions, and various other psychic symptoms (such as déjà vu or jamais vu). The medical syndrome of recurrent, unprovoked seizures is termed epilepsy, but seizures can occur in people who do not have epilepsy.
The treatment of epilepsy is a subspecialty of neurology; the study of seizures is part of neuroscience. Doctors who specialize in epilepsy are epileptologists; doctors who specialize in the treatment of children with epilepsy are pediatric epileptologists.
Seizures can cause involuntary changes in body movement or function, sensation, awareness, or behavior. A seizure can last from a few seconds to status epilepticus, a continuous seizure that will not stop without intervention. Seizures are often associated with a sudden and involuntary contraction of a group of muscles and loss of consciousness. However, a seizure can also be as subtle as marching numbness of a part of the body, a brief or long term loss of memory, sparkling or flashes, sensing/discharging of an unpleasant odor similar to alcohol base being produced by internal organs, a strange epigastric sensation or a sensation of fear and total state of confusion which in some cases leads to death during seizure. Therefore seizures are typically classified as motor, sensory, autonomic, emotional or cognitive. After a heavy seizure attack, since the brain is recovering, there is a sudden loss of memory; usually the short term memory.
In some cases, the full onset of a seizure event is preceded by some of the sensations described above. These sensations can serve as a warning to the sufferer that a full tonic-clonic seizure is about to occur. These "warning sensations" are cumulatively called an aura. Also, it is commonly believed among healthcare providers that many seizures, especially those in children, are preceded by tachycardia that frequently persists throughout the seizure. This early increase in heart rate may supplement an aura as a physiological warning sign of an imminent seizure.
Symptoms experienced by a person during a seizure depend on where in the brain the disturbance in electrical activity occurs. Recent studies show that seizures happen in sleep more often than was thought. A person having a tonic-clonic seizure may cry out, lose consciousness and fall to the ground, and convulse, often violently. A person having a complex partial seizure may appear confused or dazed and will not be able to respond to questions or direction. Some people have seizures that are not noticeable to others. Sometimes, the only clue that a person is having an absence seizure is rapid blinking, extreme confusion for a few seconds or sometimes into hours.