The two categories of seizures are generalized and focal.
Generalized seizures are caused by abnormal electrical impulses in the brain and typically occur with no warning. There are six types of generalized seizures.
- Tonic-clonic (grand-mal) Seizure — This seizure causes you to lose consciousness and often collapse. Your body becomes stiff during what's called the "tonic" phase. During the "clonic" phase, muscle contractions cause your body to jerk. Your jaws clamp shut and you may bite your tongue. Your bladder may contract and cause you to urinate. After one to two minutes, you fall into a deep sleep.
- Absence (petit mal) Seizure — During these brief episodes, you lose awareness and stare blankly. Usually, there are no other symptoms. They tend to begin and end suddenly and last for about five to 10 seconds, although they can last longer. These seizures may occur several times a day.
- Myoclonic Seizure — These very brief seizures cause your body to jerk, as if shocked by electricity, for a second or two. The jerks can range from a single muscle jerking to involvement of the entire body.
- Clonic Seizure — This seizure cause rhythmic jerking motions of the arms and legs, sometimes on both sides of your body.
- Tonic Seizure — Tonic seizures cause your muscles to suddenly stiffen, sometimes for as long as 20 seconds. If you're standing, you'll typically fall.
- Akinetic or Atonic Seizure — This seizure causes your muscles to relax or lose stength, particularly in the arms and legs. Although you usually remain conscious, it can cause you to suddenly fall and lead to injuries. These seizures also are called "drop attacks."
Focal seizures, also known as local or partial seizures, are caused by abnormal electrical activity in a specific, smaller part of the brain. The part of the brain causing the seizure is called the seizure focus. Focal seizures are divided into simple and complex seizures.
Some focal seizures evolve into generalized ones and are called secondarily generalized seizures.
- Simple Focal Seizure — During these seizures, you remain conscious although some people can't speak or move until the seizure is over. Uncontrolled movements, such as jerking or stiffening, can occur throughout your body. You also may experience emotions such as fear or rage or even joy; or odd sensations, such as ringing sounds or strange smells. In addition, you may experience peculiar memories such as a feeling of "deja-vu." Typically, these seizures last less than one minute.
- Complex Focal Seizure — During these seizures, you are not fully conscious and may appear to be in a dreamlike state. Typically, they start with a blank stare. You may involuntarily chew, walk, fidget, or perform other repetitive movements or simple actions, but actions are typically unorganized or confused. These seizures typically last betwen 30 seconds and a minute.
- Secondarily Generalized Seizure — These seizures begin as a focal seizure and develop into generalized ones as the the electrical abnormality spreads throughout the brain. When the seizure begins, you may be fully conscious but then lose consciousness and experience convulsions as it develops.
Reviewed by health care specialists at UCSF Medical Center.