Epilepsy is a debilitating neurological disorder characterized by repeated seizures of various types and severity. In this section, we discuss the causes, signs, and symptoms of seizures, as well as how they’re classified and what’s going on in the brain during a seizure.

What is a seizure?

A seizure is an electrical disturbance that interferes with normal brain function; they occur when abnormal electric signals from the brain change the way the body functions.

What causes seizures?

In general, seizures result from abnormal circuit activity in the brain. Events, ranging from faulty wiring during brain development, brain inflammation, physical injury or infection can lead to a seizure. However, according to recent estimates, in up to 50% of patients diagnosed with epilepsy, the cause is unknown (idiopathic).

According to Dr. Michael Smith, director of the Rush Epilepsy Clinic:

“The brain is an electrical organ and you could think of [a seizure] as a short circuit in one area of the brain. If you put it in computer terms, you could think of the brain as a network of computers… A focal seizure a is a short circuit in one of the computers of the network, while a generalized seizure is a short circuit in the entire network. The disturbance of the behavior depends on where that short circuit occurs.”

What are different types of seizures?

There are many different types of seizures, but they can be grouped into two broad categories, generalized or focal, depending on how they start and where they start.


Generalized seizures involve both sides of the brain and can result in loss of consciousness, falls, or massive muscle contractions. The types of generalized seizures are:

  • Absence (previously called petit-mal)
  • Atonic
  • Clonic
  • Tonic
  • Myoclonic
  • Tonic-clonic (previously called grand-mal)


Formerly known as “partial” seizures, focal seizures are localized to one side of the brain and affect approximately 60% of people with epilepsy. Focal seizures can also become generalized seizures. The types of focal seizures are:

  • Autonomic focal seizures
  • Motor focal seizures
  • Psychological focal seizures
  • Sensory focal seizures

Phases of Seizures

In addition to the various types of seizures, there are also four distinct phases of seizures: prodromal, early ictal (the “aura”), ictal, and post-ictal. However, because different forms of epilepsy affect people in different ways, individuals may or may not experience all four of phases.

Seizure signs and symptoms

Much like the phases of seizures, signs and symptoms will vary person-to-person and depend upon the type, severity, and phase of seizure. During the ictal phase, for example, a patient may experience symptoms ranging from confusion and memory lapses to vision loss and the inability to move or speak.

After a seizure ends, they may experience drowsiness, nausea, or general malaise; post-seizure symptoms may last minutes or even days.

Learn More About Seizures


Phases of Seizures


Seizing Life: All About Seizures


Webinar: The New Way to Describe Your Seizure Type


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