Seizure types
Doctors categorize seizures into two main types—generalized seizures and focal seizures. The type of seizure depends on what part of the brain is affected and the symptoms a person has during the seizure.
Generalized seizures happen when abnormal electrical activity affects the entire brain at the same time. Generalized seizures include:
- Absence seizures: Also known as petit mal seizures, people who have absence seizures have staring spells or periods of unresponsiveness or "spacing out." When the seizure ends, the person has no memory of it.
- Atonic seizures: These types of seizures are also known as drop attacks. People having these seizures lose complete control of their muscles and fall suddenly to the ground or slump over if seated. These seizures carry a high risk of injury due to falls.
- Clonic seizures: These types of seizures involve involuntary muscle twitching or convulsions that happen seemingly out of nowhere, with no muscle tensing first.
- Generalized tonic-clonic seizures: Also called grand mal seizures, these most easily recognized seizures occur in two phases. In the tonic phase, muscles stiffen, and people fall unconscious. The clonic phase follows, with uncontrolled muscle jerking or convulsions.
- Myoclonic seizures: These types of seizures involve quick jerking or twitching of one muscle or a group of related muscles. If the jerking happens in a leg, it may lead to falling and possible injury.
- Tonic seizures: These types of seizures involve muscle stiffening and falling, but no convulsions. These are also sometimes known as drop attacks because they cause falling.
Focal or partial seizures begin in a region on one side of the brain. People who experience focal seizures will often experience auras, which are warning signs that a seizure is about to occur. Auras are also a type of seizure.
Focal seizures are divided into two categories:
- Focal onset aware seizures: During these seizures, formerly called simple focal or partial seizures, people remain conscious and are usually aware that the seizure is happening. Focal onset aware seizures may be motor seizures affecting movement of only one part of the body or purely sensory seizures known as auras. Some examples of auras include:
- Changes in vision (blurriness, dark spots, or partial loss of vision)
- Flashing lights
- Ringing or buzzing in the ears or hearing voices
- Sudden sensations (numbness, tingling, nausea, headache, or dizziness)
- Sudden strong emotions (joy, anger, sadness, or fear)
- Sudden tastes in the mouth (metallic, salty, bitter, sweet, or acidic)
- Unusual or unpleasant smells
- Focal onset impaired awareness seizures: These seizures, formerly called complex focal or partial seizures, cause a person to become unaware of what is happening. These seizures often follow an aura. They frequently include repetitive or involuntary movements of the limbs, face, or body.
Focal seizures may spread to the other side of the brain, causing a lack of awareness, body stiffness, and jerking movements. These types of seizures are called focal to bilateral tonic-clonic seizures. These are also called grand mal seizures. It can be difficult to distinguish focal to bilateral tonic-clonic seizures from generalized tonic-clonic seizures without additional testing.