Types of Seizures

There are many different types of seizures. People may experience just one type or more than one. The kind of seizure a person has depends on which part and how much of the brain is affected by the electrical disturbance that produces seizures. Experts divide seizures into generalized seizures (absence, atonic, tonic-clonic, tonic, myoclonic), partial (simple and complex) seizures, non-epileptic seizures and status epilepticus.

Generalized Seizures

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; tonic; myoclonic; absence; and atonic.

Generalized tonic-clonic 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).

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, shiver-like movements 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.

Tonic seizures produce a stiffness or rigidity in all muscles, last 5–15 seconds, and if the person is standing, may also result in a fall with injuries. They also occur in sleep and are resistant to drug therapy. Absence seizures are characterized by 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 episodes daily. They may occur for several months before a child is sent for a medical evaluation.

Infantile Spasms (myoclonic-tonic seizures) are clusters or repetitive seizures characterized by quick, sudden movements that start between 3 months and 2 years of age. If a child is sitting up, the head will fall forward and the arms will flex forward. If lying down, the knees will be drawn up, with arms and head flexed forward as if the baby is reaching for support. What to do: No first aid, but a doctor should be consulted immediately. This is a neurological emergency.

Partial Seizures

In partial seizures the electrical disturbance is limited to a specific area of one cerebral hemisphere (side of the brain). Partial seizures are subdivided into simple partial seizures (in which consciousness or awareness is retained) and complex partial seizures (in which consciousness is impaired or lost). Partial seizures may spread or progress to a generalized tonic-clonic seizure, in which case the classification category is partial seizures secondarily generalized.

Partial seizures are the most common type of seizure experienced by people with epilepsy. Virtually any movement, sensory or emotional symptom can occur as part of a partial seizure, including complex visual or auditory hallucinations.

Type Duration Seizure Symptoms, and Postictal (post-seizure) Symptoms

Simple Partial: 30-60 seconds, no loss of consciousness, sudden jerking, sensory phenomena, transient weakness or loss of sensation

Complex Partial: 1 to 2 minutes, may have aura (or warning – most typical is sensation in stomach), automatisms (such as lip smacking, picking at clothes, fumbling), unaware of environment, may wander, amnesia for seizure events, mild to moderate confusion during, sleepy after

Key Things to Remember about Partial Seizures
Although partial seizures affect different physical, emotional, or sensory functions of the brain, they have some things in common:

• They don't last long. Most last only a minute or two, although people may be confused and need a lot more time (2 to 30 minutes) afterwards to recover fully.
• They end naturally. Except in rare cases, the brain has its own way of bringing the seizure safely to an end after a minute or two.
• You can't stop them. In an emergency, doctors may use drugs to bring a lengthy, non-stop seizure to an end. However, the average person should wait for the seizure to run its course and try to protect the person from harm while consciousness is clouded. People who have been shown how to use a Vagus Nerve Stimulator (VNS) magnet may try to stop a seizure in that way.
• They are not dangerous to others. The movements produced by a seizure are almost always too vague, too unorganized and too confused to threaten the safety of anyone else.

Nonepileptic Seizures

Nonepileptic seizures are episodes that briefly change a person's behavior and may look like epileptic seizures. The person having non-epileptic seizures may have internal sensations that resemble those felt during an epileptic seizure. The difference in these two kinds of episodes is often hard to recognize by just watching the event, even by trained medical personnel.

But there is an important difference. Epileptic seizures are caused by abnormal electrical changes in the brain and, in particular, in its outer layer, called the cortex. Non-epileptic seizures are not caused by electrical disruptions in the brain. Non-epileptic seizures tend to be pleomorphic over time (changing in character) and longer than epileptic seizures. Non-epileptic seizures also occur only in wakefulness, whereas epileptic seizures occur in wake and sleep. Anti-epileptic drugs do not stop non-epileptic seizures.

Status Epilepticus

Most seizures end after a few moments or a few minutes. If seizures are prolonged, or occur in a series, there is an increased risk of status epilepticus. The term literally means a continuous state of seizure. If a seizure lasts longer than 5 minutes, there is a risk of it progressing to status epilepticus.