A seizure is a sudden change in consciousness or behavior caused by abnormal brain electrical activity. Many are isolated events. Repeated seizures can occur without any obvious source of provocation. The condition of repeated seizures, regardless of whether there is an identifiable cause is defined as epilepsy. A single seizure does not mean a person has epilepsy.

Under certain circumstances, anyone can experience a seizure. As many as 10 percent of Americans have a seizure at some point in their lives, according to the Epilepsy Foundation. Seizures can occur at any age, although children are at greater risk for seizures than other age groups.

Seizures involve a sudden increase in electrical activity in the brain. The nerve cells, or neurons, produce electrochemical signals that instruct other parts of the body to do certain things, such as move or feel sensations. Neurons normally produce these signals at a rate of 80 per second.

A seizure occurs when something disturbs the pattern of electrochemical signals and causes the neurons to fire at a much faster rate, sometimes up to 500 signals per second. This storm of electrical activity in the brain can result in a seizure, possibly producing changes in mood or behavior, hallucinations, involuntary muscle contractions, loss of consciousness or involuntary movements. The specific course of a seizure depends on the area of the brain affected by this electrical activity. 

Seizures are often followed by symptoms such as fatigue, drowsiness and confusion. It may take minutes or hours to return to full consciousness. Sleepiness may last for an hour or more, and a person can feel weak for up to two days following a seizure. Many people report a feeling of confusion or extreme tiredness. This is called the postictal syndrome.

Infants experiencing seizures can display repetitive movements, decreased alertness, weakness and irritability. Children who have seizures can fall into a deep sleep after the seizure ends. This is normal and enables the brain to recover after the stress of the seizure episode. They should not be awakened during this time.

A person who has experienced a seizure often has no memory of what happened during the seizure. In addition, some people can become agitated immediately following a seizure.

Seizures lasting longer than 5 minutes should be considered a medical emergency, according to the National Institute of Neurological Disorders and Stroke (NINDS). Prolonged unrelenting seizures, or status epilepticus, is life threatening. In these cases, recovery depends on how quickly the appropriate medical intervention is received. People with epilepsy have a greater risk of status epilepticus, although it can also occur in people with no prior history of seizures if an initial seizure progresses to status epilepticus.

Immediate medical attention should be sought if a person has no history of previous seizures, or if any of the following symptoms occur:

• Physical injury is sustained during the seizure
  
• Seizure lasts 5 minutes or longer
  
• There is failure to regain a normal level of consciousness within an hour after a seizure

Individuals who have seizures that result in impaired consciousness or motor functioning are advised not to drive, swim alone or participate in other activities that could be dangerous to themselves and others. Patients with infrequent seizures may not need to restrict their normal lives in any way. Most seizures do not result in death or permanent disability.

Pseudoseizures appear to be seizures, with muscle contractions and impaired consciousness, but they reveal no evidence of abnormal electrical activity in the brain. Pseudoseizures can be psychological or the result of certain medical conditions (e.g., Tourette syndrome, sleep disorders, cardiac disturbances). Some people with epilepsy can experience pseudoseizures in addition to actual seizures.