Normal brain function depends on coordinated discharges of electrical impulses. These electrical impulses allow parts of the brain to communicate with other parts of the brain, the spinal cord, nerves, and muscles. If these electrical impulses occur in a disorderly fashion, a seizure may occur. About 2% of adults have had a seizure in their lifetimes. Two-thirds of these had only one. Strong stimuli that irritate the brain such as injury, drugs, sleep deprivation, infections, fever, low blood oxygen, or very low levels of blood glucose, can cause seizures. Seizures caused by such stimuli are known as "provoked seizures."

Seizures starting before age 2 are usually caused by high fever or abnormal levels of blood sugar, calcium, magnesium, vitamin B6, or sodium. If seizures recur in infants, it may be a sign of a hereditary brain disorder. Seizures that occur in people between 2 and 14 years old often have no known cause. Seizures in adults over 25 years old may be due to injury to the brain as from head injury, stroke or a tumor. However, up to half of seizures in this age group may have no known cause. Seizures with no identifiable cause are known as "idiopathic seizures" or "unprovoked seizures."

People who have at least two unprovoked seizures that occur at different times are diagnosed with a seizure disorder. True seizures are pretty rare. Many episodes of brief unconsciousness are actually due to fainting. Seizures are diagnosed by patient history and eyewitness accounts. An accurate description of exactly what happened is needed, including such information as how fast the episode started and whether it involved abnormal muscle movements such as spasms of the head, neck or facial muscles, tongue biting, or loss of bladder control. Also important is how long the episode lasted and how quickly the person recovered. Most seizures last for 2 to 5 minutes. Characteristics of a seizure are determined by which part of the brain is affected. To help in the diagnosis, doctors will record electrical activity in the brain using an electroencephalogram (EEG). Blood work to measure levels of calcium, glucose and sodium in the blood are also used in diagnosis to determine if the liver and kidneys are functioning properly. A complete blood count may be used to determine if anemia (low red blood cell count) may be causing a lack of oxygen to the brain or if infection (a high white cell count) may be causing the seizures. An electrocardiogram (ECG) may be ordered to determine if abnormal heart rhythm may be causing abnormal blood flow to the brain. A CT or MRI scan of the brain may be used to determine if there is damage to the brain. A spinal tap may be used to determine if an infection of the cerebrospinal fluid may be the cause.

The first goal of treatment is to identify and avoid the cause of the seizure. If the cause cannot be identified, medications are used to control seizures. There are many different types of seizures. Partial seizures affect only one side of the brain. Partial seizures may be simple where consciousness is not lost or complex where consciousness is impaired. Generalized seizures affect large areas on both sides of the brain, loss of consciousness, and abnormal movements. About 70% of patients have only one type of seizure. Medications are chosen based on the type of seizure. Anticonvulsant medications all have side effects. Blood tests may be required to monitor effects on liver and kidneys. Anticonvulsant medication doses are critical and they must be taken exactly as directed. Patients on anticonvulsant medications should wear a Medic Alert bracelet.

Reference: http://www.merck.com/mmhe/sec06/ch085/ch085a.html.

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