Absence seizure

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Maham Khan [2] Kiran Singh, M.D. [3]

Overview

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.

Classification

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 3 and 12.

Epilepsy is the most common cause of recurrent seizures, but most seizures are single events that do not recur. Single seizures can be caused by blows to the head, fever (febrile seizure), reactions to medications, tumors, 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 have repeated absence seizures that 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. 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. 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 usually stops when the child reaches puberty. Absence seizures usually have no lasting effect on intelligence or other brain functions.

It is well known that bright lights, loud noises, and other strong sensory stimuli may trigger seizure episodes.[4]

A person having an absence seizure shows no emotional expressions during the absent period. This indicates that a certain level of consciousness and arousal are needed to experience emotions.

Causes

Life Threatening Causes

Life-threatening causes include conditions which may result in death or permanent disability within 24 hours if left untreated.

• Asphyxia
• Stroke

Common Causes

• Childhood absence epilepsy

Causes by Organ System

Cardiovascular	Stroke
Chemical/Poisoning	Famine, fetal alcohol spectrum disorder, fetal alcohol syndrome, lindane
Dental	No underlying causes
Dermatologic	Systemic lupus erythematosus
Drug Side Effect	Acetazolamide, beclamide, DPT vaccine, etomidate, heroin, metformin, modafinil, olanzapine, trazodone
Ear Nose Throat	No underlying causes
Endocrine	Diabetes mellitus, hypoglycemia, ketotic hypoglycemia, oxytocin, polydipsia, prolactin, psychogenic polydipsia
Environmental	No underlying causes
Gastroenterologic	No underlying causes
Genetic	Angelman syndrome, Joubert syndrome, Lennox-Gastaut syndrome, Mowat-Wilson syndrome, spinocerebellar ataxia
Hematologic	Porphyria
Iatrogenic	No underlying causes
Infectious Disease	AIDS, meningitis
Musculoskeletal/Orthopedic	No underlying causes
Neurologic	Encephalopathy, hydrocephalus, meningitis, porencephaly, postictal state, Rasmussen's encephalitis, shaken baby syndrome, spinocerebellar ataxia, stroke, traumatic brain injury
Nutritional/Metabolic	No underlying causes
Obstetric/Gynecologic	Menopause
Oncologic	No underlying causes
Ophthalmologic	No underlying causes
Overdose/Toxicity	No underlying causes
Psychiatric	No underlying causes
Pulmonary	Asphyxia
Renal/Electrolyte	Dehydration, systemic lupus erythematosus
Rheumatology/Immunology/Allergy	Systemic lupus erythematosus
Sexual	No underlying causes
Trauma	Traumatic brain injury
Urologic	No underlying causes
Miscellaneous	No underlying causes

Causes in Alphabetical Order

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Complete Differential Diagnosis of causes of Absence seizure

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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 valproic acid (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. [5] 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.

The U.S. government is currently sponsoring such a study. [6] 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.

Related Chapters

• Childhood absence epilepsy
• Tonic-clonic seizure

External Links

• This article is based on text taken from the public domain NINDS document "Seizures and Epilepsy: Hope Through Research"
• Clinical Trial: Childhood Absence Epilepsy Rx PK-PD-Pharmacogenetics Study
• Epilepsy.com
• Mayo Clinic on Petit Mal (Absence) Seizures
• Mechanisms of absence seizures (Scholarpedia)