Generalized seizures affect both cerebral hemispheres (sides of the brain) from the beginning of the seizure. They produce loss of consciousness, either briefly or for a longer period of time, and are sub-categorized into several major types:
Generalized tonic clonic seizures (grand mal seizures) are the most common and best known type of generalized seizure. They begin with stiffening of the limbs (the tonic phase), followed by jerking of the limbs and face (the clonic phase).
During the tonic phase, breathing may decrease or cease altogether, producing cyanosis (blueing) of the lips, nail beds, and face. Breathing typically returns during the clonic (jerking) phase, but it may be irregular. This clonic phase usually lasts less than a minute.
Some people experience only the tonic, or stiffening phase of the seizure; others exhibit only the clonic or jerking movements; still others may have a tonic-clonic-tonic pattern.
Incontinence may occur as a result of the seizure. The tongue or inside of the mouth may be bitten during the episode; breathing afterwards may be noisy and appear to be labored. Contrary to popular belief, nothing should be placed in the mouth during the seizure; turning the patient on one side will help prevent choking and keep the airway clear.
Following the seizure, the patient will be lethargic, possibly confused, and want to sleep. Headache sometimes occurs. Full recovery takes minutes to hours, depending on the individual.
Myoclonic seizures are rapid, brief contractions of bodily muscles, which usually occur at the same time on both sides of the body. Occasionally, they involve one arm or a foot. People usually think of them as sudden jerks or clumsiness. A variant of the experience, common to many people who do not have epilepsy, is the sudden jerk of a foot during sleep. First aid is usually not needed, however, a person having a myoclonic seizure for the first time should receive a thorough medical evaluation.
Atonic seizures produce an abrupt loss of muscle tone. Other names for this type of seizure include drop attacks, astatic or akinetic seizures. They produce head drops, loss of posture, or sudden collapse. Because they are so abrupt, without any warning, and because the people who experience them fall with force, atonic seizures can result in injuries to the head and face. Protective headgear is sometimes used by children and adults; the seizures tend to be resistant to drug therapy. No first aid is needed (unless there is injury from the fall), but if this is a first atonic seizure, the child should be given a thorough medical evaluation.
Absence seizures (also called petit mal seizures) are lapses of awareness, sometimes with staring, that begin and end abruptly, lasting only a few seconds. There is no warning and no after-effect. More common in children than in adults, absence seizures are frequently so brief that they escape detection, even if the child is experiencing 50 to 100 attacks daily. They may occur for several months before a child is sent for a medical evaluation.
More common in children than in adults, absence seizures almost always start between ages 4 and 12 years, and rarely do they begin after age 20. Absence seizures are characterized by a brief impairment of consciousness, which usually lasts no more than a few seconds. The child, whether sitting or standing, simply stares vacantly; neither speaking nor apparently hearing what is said. Then, as abruptly as it began, the impairment lifts and the child continues with his or her previous activity. However, a brief segment of unawareness has been imposed in the stream of activity or thought. Automatisms may occur in prolonged absence seizures. Absence seizures are frequently so brief that they escape detection, even if the child is experiencing 50 to 100 attacks daily. They may occur for several months or even years before a child is sent for a medical evaluation.
Some absence seizures are accompanied by brief myoclonic jerking of the eyelids or facial muscles, or by variable loss of muscle tone. More prolonged attacks may be accompanied by automatisms, which may lead them to be confused with complex partial seizures. However, complex partial seizures last longer, may be preceded by an aura, and are usually marked by some type of confusion following the seizure.
Absence seizures may occur only occasionally or more than 100 times a day. Most children with typical absence seizures are otherwise normal. Although manifestations of their seizures are usually subtle, these children need prompt and effective treatment because absence seizures can interfere with learning. About half the children also have infrequent generalized tonic-clonic seizures. The electroencephalographic (EEG) pattern of diffuse spike-wave is closely correlated with absence seizures.
Absence seizures are often confused with complex partial seizures. This is an unfortunate mistake because the drugs that prevent absence seizures have little or no effect on complex partial seizures. Conversely, the most effective drugs for complex partial seizures are either ineffective against or increase the frequency of absence seizures.
Although absence and complex partial seizures can be confused, they have distinct differences. First, absence seizures are never preceded by an aura. Second, absence seizures are of briefer duration – seconds rather than minutes. Third, absence seizures begin frequently and end abruptly. Finally, the absence attack is always associated with the strikingly typical EEG abnormality of spike and slow wave discharges, usually at a frequency of 3Hz. These discharges can occur interictally and ictally and are often provoked by hyperventilation.