Types of Seizures
Expert: Robert S. Fisher, M.D. Professor of Neurology Stanford University »
Seizures is a medical condition that is divided into two types. Watch our video to learn in detail about the different types of seizures and how to manage them.
The word “seizure” is used to describe the medical condition in which too many brain cells become excited simultaneously, but there are actually so many that neurologists are still updating how to classify them. Usually, they classify seizures into two main types, partial seizures and primary generalized seizures.
The difference between these types is in how they begin: Partial seizures, which begin in a single part of the brain, are further described by two additional criteria.
- The first is whether awareness, memory, and consciousness are preserved during the seizure. If they all are preserved, then a seizure is called “simple partial.”
- However, if any are impaired then the seizure is called “complex partial.”
The impact of a partial seizure depends on where in the brain it originates, and how it spreads. Partial seizures sometimes have an aura, which is a warning that bigger seizures may follow. An aura usually occurs seconds to minutes before seizure, but some patients can have periods of warning lasting a day or longer. Technically, the aura is itself a small simple partial seizure. There are many different ways in which people experience an aura. The start of a seizure in one of the temporal lobes can produce unusual feelings, like abnormal sensation or forced thinking. The onset of a complex partial seizure may be heralded by deja vu, a familiar feeling, or jamai vu, an unfamiliar feeling. Some patients have auras of sounds, tastes, distorted vision, racing thoughts, or smells, like burning rubber. Physical sensations occurring as auras are dizziness, headache, lightheadedness, and numbness. An upset stomach is a particularly common phsycial symptom. Auras can include a sense of tingling rising up the body or other strange feelings difficult to describe. Distorted emotions, like fear or panic, can also be a seizure warning. However, some complex partial seizures occur without any remembered warning. Primarily generalized seizures begin with a widespread electrical discharge that involves both sides of the brain at once. Partial seizures begin with an electrical discharge in one limited area of the brain. All generalized seizures begin with synchronous electrical activity throughout the brain accompanied by sudden generalized movements or loss of consciousness.
However, there are still many different types of generalized seizure. A tonic-clonic seizure, once called a “grand mal,” is what most people think of when they hear the word “seizure.” When someone experiences a tonic-clonic seizure, first they stiffen and lose consciousness, which is the “tonic” phase. Then, they begin jerking, which lasts for several minutes and is called the “clonic” phase.
Sometimes seizures don’t have a tonic stiffening and clonic jerking sequence, but are just tonic seizures or clonic seizures.
- Other types of generalized seizure include absence seizures, when the sufferer “disconnects” from the world for a few seconds,
- myoclonic seizures, which cause jerking, but just for a second or two,
- and atonic seizures, which cause people to lose all muscle tone and drop to the ground.
Understanding the different types of seizures can be helpful, but many people want more detailed information. The next two videos in this series provide an in-depth look at the effect of partial seizures on different parts of the brain and the different types of generalized seizures. “The movies in this series can be viewed in any order. If you wish to watch these clips in their original sequence, the next clip is, “Understanding the Different Types of Partial Seizures.”