In 2017, the International League Against Epilepsy (ILAE) released updated classifications for epilepsy. The new classifications better reflect current scientific understanding of seizures, as the prior classifications had last been updated in 1989.

Before this new update, seizures were divided into two broad categories — partial-onset seizures and generalized seizures. Partial-onset seizures originate in one side, or hemisphere, of the brain and generalized seizures start in both sides of the brain.

The new classification considers three main factors when defining seizures:

1. Point of origin
2. Awareness level
3. Behaviors

For example, simple partial seizures have been renamed focal onset aware seizures, and complex partial seizures have been reclassified as focal onset impaired awareness seizures.

Why the changes? In an interview in Epigraph, Ingrid Scheffer, who led the ILAE effort to reclassify seizures, said the group was focused on creating “transparent language” for seizure types. “We wanted language that patients could understand, not just doctors,” she said.

Current Classification of Types of Seizures

Seizure type is now identified by point of origin, awareness level, and accompanying behaviors.

Point of Origin

The point of origin for each type of seizure is now classified into one of four categories:

• Focal onset — Formerly known as a “simple partial seizure,” focal onset seizures originate within networks limited to one hemisphere of the brain. They may be localized to one small area of the brain or more widely distributed.
• Generalized onset — These originate within and rapidly engage areas in both sides of the brain at once.
• Unknown onset — As the name suggests, the origin of these seizures is unknown.
• Focal to bilateral seizure — These seizures start on one side of the brain and spread to both sides.

Awareness Level

Awareness levels during seizures have four distinguishing features:

• Focal aware — During focal aware seizures, a person is aware, but may be unable to talk or respond.
• Focal impaired awareness — Formerly known as a “complex partial seizure,” a focal impaired awareness seizure occurs when a person’s awareness is impacted at some point during a seizure.
• Awareness unknown — This classification is used when a seizure takes place with no witness to observe awareness levels.
• Generalized seizures — Generalized seizures, which affect both halves of the brain, usually always affect a person’s awareness or level of consciousness in some way.

Behaviors

Behaviors that accompany focal onset seizures also have classifications:

• Focal motor seizure — This term describes a seizure accompanied by movement, such as stiffening, thrashing, jerking, or automatic movements like walking or running.
• Focal nonmotor seizure — This is a seizure with other symptoms that precede it, such as changes in thinking, emotions, or sensation.

These behaviors accompany generalized onset seizures:

• Generalized motor seizure — “Tonic-clonic seizures,” with their characteristic stiffening and jerking motions, is still an accurate term. However, the term “grand mal seizure” that often accompanied that description is no longer used.
• Generalized nonmotor seizure — “Absence seizures,” with brief changes in awareness that include staring and some repeated movements, is the new classification. This has replaced “petit mal seizures.”

Read more about types of focal seizures and their treatments.

Scientific Progress in Understanding Epilepsy

Understanding the history of epilepsy research can shed light on how and why terminology has changed, and why the current set of terms is the most accurate so far. The ancient Greeks coined the term epilepsy (meaning “to seize”) and attributed the condition to an attack by a demon or a god. Babylonians documented seizures on clay tablets. Ancient Persians believed the source was mental illness, while Chinese physicians more than 2,500 years ago believed epilepsy was caused by an excess of secretions in the brain.

By the 1860s, British neurologist John Hughlings Jackson had determined that seizures were due to activity in the brain. For the first time, he hypothesized that seizures present differently depending upon the part of the brain from which they originated. In the 1930s, this groundbreaking theory inspired Canadian-American neurosurgeon Wilder Graves Penfield to use electrostimulation in surgery to locate the brain tissue responsible for behavior during a seizure. Once identified, he pioneered the concept of removing this affected tissue. Henri Jean Pascal Gastaut took that research one step further, working with his wife, Yvette, to define five major human electroencephalogram (EEG) patterns. He also discovered Gastaut syndrome (photosensitive epilepsy) and Lennox-Gastaut syndrome (severe childhood encephalopathy).

Significant advances in diagnostic imaging have been made in the last 50 years. New imaging tools include computerized tomography (CT) scans, magnetic resonance imaging (MRI), single photon emission computerized tomography (SPECT) and positron-emission tomography (PET), magnetic resonance spectroscopy, and magnetoencephalography (MEG). With each new tool, scientists have become better able to understand brain activity. These tools have also dramatically changed the possibilities of surgery as a treatment for epilepsy. In more recent times, advances in imaging have led to the possibility of neuromodulation — using devices that electrically stimulate the nervous system — to treat epilepsy in a less invasive way.

Collaboration and Education

As scientists gained a deeper understanding of the brain and epilepsy, formal organizations were established to study epilepsy, share knowledge, and improve care. The International Bureau for Epilepsy (IBE) was established in 1961 to study the medical and nonmedical aspects of epilepsy. In 1966, the surgeon general of the United States created the Public Health Service Advisory Committee on the Epilepsies.

The International League Against Epilepsy took a leadership role in 1969 when it accepted the first “Clinical and electroencephalographic classification of epileptic seizures” at its General Assembly in New York. The new standards created common terminology for epilepsy. A shared set of terminology facilitated improved communication and information-sharing among researchers and physicians. Those original classifications were updated in 1981 and 1989 before the most recent update in 2017.

Talk With Others

MyEpilepsyTeam is the social network for people with epilepsy and their loved ones. On MyEpilepsy, more than 108,000 members come together to ask questions, give advice, and share their stories with others who understand life with seizures.

Have you been diagnosed with epilepsy? Do you have questions about seizure terms? Share your experience in the comments below, or start a conversation by posting on your Activities page.