What are the different types of clinical seizures?
There are different types of seizures, which traditionally have been categorized as either generalized seizures or partial seizures. Generalized seizures are those in which the clinical manifestations indicate that the whole brain is involved from the beginning of the seizure. Partial seizures (local, focal) are those in which the epileptic event is limited to one part of the body or to a particular function of the brain, indicating that the epileptic seizure started in one limited area of the brain. Partial seizures may remain focal or may expand to the rest of the brain. When seizures expand to the rest of the brain these are referred to as secondary generalized seizures. Consciousness is always impaired in generalized seizures; however, in the case of partial seizures consciousness may be preserved , as in the so-called simple partial seizures, or it may be impaired, as is the case with the complex partial seizures.
Among the generalized seizures, the generalized tonic clonic seizure (traditionally recognized as a grand mal seizure) is the most common type. In this seizure there is a succession of muscle contractions (tonic component), more obvious in the extremities but affecting almost every muscle of the body, followed by sudden relaxation (clonic component) and further followed by another tonic component. This succession of events is repeated several times.
Simultaneously, there are other signs and symptoms including dilatation of the pupils, increased heart rate, and increased blood pressure. Cyanosis (skin and lips turning blue-purple) is also seen due to persistent contraction of the diaphragm muscle and holding of the breath. These convulsions are usually followed by a period of confusion. In most instances these seizures, as well as most of the epileptic seizures, last for a few seconds or at the most for 2-3 minutes. Occasionally the seizure event may be prolonged, lasting several minutes. By definition, when the event lasts more than 30 minutes, it is described as status epilepticus.
Another type of generalized seizure is the absence seizure, also called petit mal seizure, because the clinical symptoms are not as dramatic as with the generalized tonic clonic seizures. In the absence seizures, as the name implies, the patient looks absent, like "not being here." With this type of seizure there is a sudden interruption of activities, and the patient becomes unresponsive. Usually these seizures, particularly when they last longer than a few seconds, are associated with other subtle clinical signs such as eye blinking or twitching in the face or upper body. There is almost no confusion after these seizures, and the patient returns to his/her activities without even acknowledging that a seizure has occurred.
In the atonic seizures (drop attacks) there is a sudden loss of muscle activity, like a sudden paralysis. The patient will collapse like a marionette when all its strings are cut at once. If these seizures happen when the individual is walking, a fall will result, or if the patient is seated, he/she will experience a sudden drop of the head, usually without the motor reflexes that help people to prevent injuries. These seizures are very brief and might result in serious injuries, most often to the forehead, mouth, and/or face.
The myoclonic seizures consist of rapid, jerky contractions of isolated muscles or group of muscles which may or may not result in body movements.
The tonic seizures consist of a brief stiffening of the muscle groups, resulting most often in extension of the arms or legs or arching of the trunk. Some of these seizures might be associated with a forced exhalation of air, due to a sudden contraction of the expiratory muscle through partially contracted vocal cords, resulting in a loud sound.
Partial (focal, local) seizures
With partial (focal, local) seizures, the clinical events originate in a limited area of the brain. The clinical manifestations depend upon the area of the brain that is abnormal. Many different clinical events can be seen with this type of seizure.
For example, with simple partial seizures (consciousness is not impaired) if the focal area of the brain involved is the motor area, the patient might have rhythmic contractions in one arm or leg. If the areas compromised are more involved with the visual system then the patient might complain of visual illusions.
Other abnormal sensations might be the result of lesions in the auditory, olfactory, or gustatory areas. Some other symptoms might include:
- epigastric pain,
- pallor (paleness),
- pupillary dilatation,
- a sense of "déjá vu,"
- fear or anger.
These patients are conscious when the symptoms occur, and their description of the symptoms can be very useful in determining which area of the brain is involved in the seizure. This has important implications for the selection of the appropriate treatment, especially for the decision about the need for surgery.
The complex partial seizures (sometimes called "temporal lobe seizures" or "psychomotor seizures"), in which consciousness is impaired, have a greater range of symptoms. The symptoms already described in the simple partial seizures might be present and might be followed by complex automatic behaviors such as manipulating objects, walking around the room, or answering questions, usually done in a rumbling, difficult-to-understand language.