In seizure, there is uncontrolled, excessive electrical discharge by the neurons in the brain. Epilepsy is a brain disorder characterized by recurrent seizures, but seizures can also be caused by brain disorders such as stroke, tumor or hypoglycemia. There are two broad categories of seizure: partial seizures and generalized seizures.

Partial seizures affect a single side of the brain. Simple partial seizures often are marked only by a sudden, brief interruption of activity; when the seizure passes, the patient may be unaware that a seizure has occurred. Complex partial seizures involve a brief loss of consciousness. Partial seizures often begin in a particular site in the brain, most commonly the medial temporal lobe.

Complex seizures affect both sides of the brain. In some cases, the seizure begins in both sides simultaneously; in other cases, the seizure begins on one side and spreads to the other side. There may be a sudden loss of consciousness and muscle spasms, with possible tongue-biting and incontinence. After consciousness is regained, the patient may be lethargic and confused for some time.