|Synonyms||Fever fit, febrile convulsion|
|An analog medical thermometer showing a temperature of 38.8 °C or 101.8 °F|
|Specialty||Emergency medicine, neurology|
|Usual onset||Ages of 6 months to 5 years|
|Duration||Typically less than 5 minutes|
|Causes||High body temperature|
|Risk factors||Family history|
|Similar conditions||Meningitis, metabolic disorders|
|Medication||Benzodiazepines (rarely needed)|
|Frequency||~6% of children|
A febrile seizure, also known as a fever fit or febrile convulsion, is a seizure associated with a high body temperature but without any serious underlying health issue. They most commonly occur in children between the ages of 6 months and 5 years. Most seizures are less than five minutes in duration and the child is completely back to normal within sixty minutes of the event.
Febrile seizures may run in families. The diagnosis involves verifying that there is not an infection of the brain, there are no metabolic problems, and there have not been prior seizures that have occurred without a fever. There are two types of febrile seizures: simple febrile seizures and complex febrile seizures. Simple febrile seizures involve an otherwise healthy child who has at most one tonic-clonic seizure lasting less than 15 minutes in a 24-hour period. Blood testing, imaging of the brain or an electroencephalogram (EEG) is typically not needed for the diagnosis. Examination to determine the source of the fever is recommended. In otherwise healthy looking children a lumbar puncture is not necessarily required.
Neither anti-seizure medication nor anti-fever medication are recommended in an effort to prevent further simple febrile seizures. In the few cases that last greater than five minutes a benzodiazepine such as lorazepam or midazolam may be used. Outcomes are generally excellent with similar academic achievements to other children and no change in the risk of death for those with simple seizures. There is tentative evidence that children have a slight increased risk of epilepsy at 2%. Febrile seizures affect two to ten percent of children before the age of five. They are more common in boys than girls. After a single febrile seizure there is a 15 to 70% chance of another one.
Signs and symptoms
During generalized febrile seizures, the body will become stiff and the arms and legs will begin twitching. The child loses consciousness, although their eyes remain open. Breathing can be irregular. They may become incontinent (wet or soil themselves); they may also vomit or have increased secretions (foam at the mouth). The seizure normally lasts for less than five minutes. The child's temperature is usually greater than 38 °C (100.4 °F).
Febrile seizures are due to fevers, usually those greater than 38 °C (100.4 °F). The cause of the fevers is often a viral illness. The likelihood of a febrile seizure is related to how high the temperature reaches. Some feel that the rate of increase is not important while others feel the rate of increase is a risk factor. This latter position has not been proven.
Another factor that increases the risk is a number of vaccines. This increase in risk, however, is small. Implicated vaccines include measles/mumps/rubella/varicella, diphtheria/tetanus/acellular pertussis/polio/Haemophilus influenzae type b, whole-cell pertussis, some versions of the pneumococcal vaccine, and some types of influenza vaccine when given together with the pneumococcal vaccine or diphtheria/tetanus/acellular pertussis vaccine.
The seizures occur, by definition, without an intracranial infection or metabolic problems. They run in families. Several genetic associations have been identified. An association with iron deficiency has also been reported, particularly in the developing world.
The diagnosis is arrived at by eliminating more serious causes of seizure and fever: in particular, meningitis and encephalitis. However, in locales in which children are immunized for pneumococcal and Haemophilus influenzae, the prevalence of bacterial meningitis is low. If a child has recovered and is acting normally, bacterial meningitis is very unlikely.
There are three types of febrile seizures.
- A simple febrile seizure is characterized by shorter duration (lasting less than 15 minutes), no focal features (meaning the shaking is general rather than restricted to a part of the body such as an arm or leg), and if they do occur in series, the total duration is less than 15 minutes (classically a generalized tonic-clonic seizure).
- A complex febrile seizure is one in which the seizure lasts longer than 15 minutes or multiple episodes occur within 24 hours and generally does have focal features.
- A febrile status epilepticus is a febrile seizure that lasts for longer than 30 minutes. It can occur in up to 5% of febrile seizure cases.
In those with a history of febrile seizures, neither antipyretic or anticonvulsant medications have been found effective for prevention; however, some appear to be associated with harm.[needs update] They are thus not recommended as an effort to prevent further seizures.
The vast majority of people do not require treatment for either their acute presentation or for reoccurrences. In those who have prolonged seizures intravenous lorazepam is recommended. The other benzodiazepines—midazolam and diazepam—are also reasonable options.
Long term outcomes are generally good with little risk of neurological problems or epilepsy. Those who have one febrile seizure have an approximately 40% chance of having another one in the next two years, with the risk being greater in those who are younger.
Simple febrile seizures do not tend to recur frequently (children tend to outgrow them) and do not make the development of adult epilepsy significantly more likely (about 3–5%) compared with the general public (1%). Children with febrile convulsions are more likely to have a febrile seizure in the future if they were young at their first seizure (less than 18 months old), have a family history of a febrile convulsions in first-degree relatives (a parent or sibling), have a short time between the onset of fever and the seizure, had a low degree of fever before their seizure, or have a seizure history of abnormal neurological signs or developmental delay. Similarly, the prognosis after a complex febrile seizure is excellent, although an increased risk of death has been shown for complex febrile seizures, partly related to underlying conditions.
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