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Absence seizures are one of several kinds of seizures. These seizures are sometimes referred to as petit mal seizures, which is an older term.

In absence seizures, the person may appear to be staring into space with or without jerking or twitching movements of the eye muscles. These periods last for seconds, or even tens of seconds. Those experiencing absence seizures sometimes move from one location to another without any purpose. Under normal circumstances thalamocortical oscillations maintain normal consciousness of an individual, however in certain circumstances the normal pattern can become disrupted; thereby leading to an episode of absence. Drugs, such as ethosuximide work by binding to t-type Ca2+ channels on thalamic neurones to modify these oscillations and prevent these episodes from occurring.

Types

Absence seizures may occur in several forms of epilepsy. Absence epilepsy refers to epilepsy in which the only seizures are absence seizures. Absence epilepsy is often characterized by age of onset, e.g., childhood absence epilepsy for epilepsy beginning in childhood between the ages of 4 and 12.

Epilepsy is the most common cause of recurrent seizures, where seizures are single events that reoccur with seemingly random frequency. Single seizures can be caused by blows to the head, fever (febrile seizure), reactions to medications, tumours, or as a symptom of a larger disease, among other causes.

Just as there are many different kinds of seizures, there are many different kinds of epilepsy. Doctors have identified hundreds of different epilepsy syndromes - disorders characterized by a specific set of symptoms that include epilepsy. Some of these syndromes appear to be hereditary. For other syndromes, the cause is unknown. Epilepsy syndromes are frequently described by their symptoms or by where in the brain they originate. People should discuss the implications of their type of epilepsy with their doctors to understand the full range of symptoms, the possible treatments, and the prognosis.

Presentation

People with absence epilepsy can see flashing or blinking lights(can be in corner of the eye or eyes) then a flash vision change (some find it hard to describe this sensation) in some after he or she has these symptoms slips into the seizure.^{citation needed} Repeated absence seizures that can cause momentary lapses of consciousness. These seizures almost always begin in childhood or adolescence, and they tend to run in families, suggesting that they may be genetic. Some people with absence seizures have purposeless movements during their seizures, such as a jerking arm or rapidly blinking eyes.^{citation needed} Others have no noticeable symptoms except for brief times when they are "out of it." Immediately after a seizure, the person can resume whatever he or she was doing or vomiting may occur after one eats.^[1] These seizures can happen a few times a day or in some cases hundreds of times a day to the point that the person cannot concentrate in school or other situations. Childhood absence epilepsy may stop when the child reaches puberty. Absence seizures usually have no lasting effect on intelligence or other brain functions.^{citation needed}

It is well known that bright lights, nervous, stressful, uncomfortable situations, or other strong sensory stimuli may trigger seizures.^{citation needed} Hyperventilation is also a common trigger. However, loud noises can help to either bring a person back to consciousness or keep him or her conscious.^{citation needed} Reciting one's name can be very helpful in an emergency as can repetitively asking the victim to "stay with you".^{citation needed} Such can be accomplished by counting methods, alphabets and so on.^[2]

A person having an absence seizure shows no emotional expressions during the absent period.^{citation needed} While the ability to express emotion in the face may be dissociated from the experience of emotion, the lack of any emotionally charged facial expression may indicate that a certain level of consciousness and arousal are needed to experience emotions.

A classic 3-Hz spike-and-wave EEG pattern accompanies absence seizures.^{citation needed}

Treatment

The primary goal of treatment of recurrent absence seizures is to prevent accidental injuries that may occur during seizures. For those with frequent seizures the goal of treatment includes preventing the seizures from interfering with learning at school and other activities of daily life.

The goal of treatment with medications for absence seizures is to accomplish the goals above, by eliminating or reducing the frequency of the absence seizures, without causing side-effects more serious than the epilepsy itself.

Certain anticonvulsant drugs are used to minimize the number of seizures episodes. Absence seizures appear to respond well to divalproex sodium (trade name: Depakote), ethosuximide (trade name: Zarontin), and lamotrigine (Lamictal). Each of these medications has potential side effects, some of them serious. While the most serious side effects are uncommon, a better understanding of the risks and benefits of each of these medications would benefit many parents and guardians in consenting to treatment for their children.

For absence seizures, there is insufficient evidence to know which, if any, of the available medications is best, i.e., having the best combination of safety and efficacy.^[3] Nor is it known how long medication must be continued before a trial off medication should be conducted to determine if the individual has outgrown the absence seizures, as children so often do.

To date, there have been no published results of any large, double-blind, placebo-controlled studies comparing the efficacy and safety of these or any other medications for absence seizures.^{citation needed}

The U.S. government is currently sponsoring such a study.^[4] The purpose of this study is to determine the best initial treatment for childhood absence epilepsy from among valproic acid, ethosuximide and lamotrigine. In addition, the researchers hope to develop methods that may be used in the future to help choose the best medicine for each child diagnosed with absence seizures. The 5-year study began in 2004, and is expected to involve more than 400 children.

Also included in the study will be pharmacokinetics and pharmacogenetics research. Pharmacokinetics is the study of how the body absorbs, distributes, metabolizes, and excretes drugs. Pharmacogenetics is the study of genetic determinants of the response to drugs. Knowledge gained from this study may lead to individualized treatment for children with absence seizures.

Hyperbaric Oxygen Therapy is recommended by many alternative health practitioners. Many report positive results from this technique. ^[5][6]

References

1. ^ Causes of Petit mal seizures
2. ^ "Epilepsy".
3. ^ "Ethosuximide, sodium valproate or lamotrigine for absence seizures in children and adolescents".
4. ^ "Childhood Absence Epilepsy Rx PK-PD-Pharmacogenetics Study - Full Text View - ClinicalTrials.gov".
5. ^ "Treat seizures with Hyperbaric Oxygen Therapy".
6. ^ "Undersea & Hyperbaric Medicine in San Diego, California (CA), Undersea & Hyperbaric Medicine Doctor".

2. Patten, John [1996]. "22", Neurological Differential Diagnosis., 2 Rev Ed (in English), London: Springer-Verlag London Limited, 380-1. ISBN 3-540-19937-3. 

See also

• Childhood absence epilepsy
• Tonic-clonic seizure
• Mechanisms of absence seizures (Scholarpedia)

Wikipedia content modification information:

• This page was last modified on 19 August 2008, at 19:29.

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