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A febrile seizure, also known as a fever fit or febrile convulsion, is a convulsion associated with a significant rise in body temperature. They most commonly occur in children between the ages of 6 months to 6 years (with only 10% of reported seizures occurring after the age of 3) and are twice as common in boys as in girls.
The non-profit Febrile Seizure Organisation has been set up as a resource for parents of children with febrile seizures to find out about the latest information and research into the condition, share their experiences, help with the research and get help. In particular parents can submit an anonymous Seizure Report to help with research into this condition.
Signs and symptoms
During generalized febrile seizures, the body will become stiff and the arms and legs will begin twitching. The patient 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 direct cause of a febrile seizure is not known; however, it is normally precipitated by a recent upper respiratory infection or other viral illness causing fever. A febrile seizure is the effect of a sudden rise in temperature (>39°C/102°F) rather than a fever that has been present for a prolonged length of time. Parents caring for children that may be febrile who wrap them up in warm blankets in an attempt to give comfort unknowingly increase their fever and therefore the risk.
Febrile seizures occurring in children between the ages of 6 months and about 6 years can be due to a hypersensitive hypothalamus in the brain. The hypothalamus is responsible for homeostatic core temperature regulation, (amongst other factors) and in younger children it is still a developing portion of the brain, meaning it is susceptible to hypersensitive reactions to slight raises in body temperature.
Febrile seizures represent the meeting point between a low seizure threshold (genetically and age-determined; some children have a greater tendency to have seizures under certain circumstances) and a trigger, which is fever. The genetic causes of febrile seizures are still being researched. Some mutations that cause a neuronal hyperexcitability (and could be responsible for febrile seizures) have already been discovered.
Several genetic associations have been identified. These include:
The diagnosis is one that must be arrived at by eliminating more serious causes of seizure and fever: in particular, meningitis and encephalitis must be considered. 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. The diagnosis of a febrile seizure should not prevent evaluation of the child for source of fever, although this is usually limited to evaluation of the urine in the younger age groups.
There are two 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 30 minutes (classically a generalized tonic-clonic seizure).
- A generalized febrile seizure also known as 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.
The simple seizure represents the majority of cases and is considered to be less of a cause for concern than the complex.
Simple febrile seizures do not cause permanent brain injury; 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 suffer from a febrile epileptic attack in the future if they have a complex febrile seizure, a family history of a febrile convulsions in first-degree relatives (a parent or sibling), or a preconvulsion history of abnormal neurological signs or developmental delay. There is an 80% chance that children who have complex febrile seizures will have seizures later on in life. Similarly, the prognosis after a simple febrile seizure is excellent, whereas an increased risk of death has been shown for complex febrile seizures, partly related to underlying conditions.
The vast majority of patients do not require treatment for either their acute presentation with a seizure or for recurrences. Application of a damp sponge can help. When judged by a physician to be indicated, anticonvulsants can be prescribed. Sodium valproate or clonazepam are active against febrile seizures, with sodium valproate showing superiority over clonazepam.
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