A febrile seizure, also known as a fever fit or febrile convulsion, is a convulsion triggered by a rise in body temperature. They most commonly occur in children between the ages of 3 months and 5 years and are twice as common in boys as in girls. The direct cause of a febrile seizure is not known; however, it is normally precipitated by a recent upper respiratory infection or gastroenteritis. A febrile seizure is the effect of a sudden rise in temperature (>39C/102F) rather than a fever that has been present for a prolonged length of time. 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.


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 ruled out. Therefore, a doctor!!!s opinion should be sought, and in many cases the child would be admitted to hospital overnight for observation and/or tests. As a general rule, if the child returns to a normal state of health soon after the seizure, a nervous system infection is unlikely. Even in cases where the diagnosis is febrile seizure, doctors will try to identify and treat the source of fever.


There are two types of febrile seizures. A simple febrile seizure is one in which the seizure lasts less than 15 minutes, does not recur in 24 hours, and involves the entire body (classically a generalized tonic-clonic seizure). A complex febrile seizure is characterized by longer duration, recurrence, or focus on only part of the body. 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 generally 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 35%, which is similar to that of the general public). Children with febrile convulsions are more likely to suffer from afebrile epileptic attacks in the future if they have a complex febrile seizure, a family history of afebrile convulsions in first-degree relatives (a parent or sibling), or a preconvulsion history of abnormal neurological signs or developmental delay. 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.


During simple febrile seizures, the body will become stiff and the arms and legs will begin twitching. The patient may lose consciousness and possibly wet or soil themselves; they may also vomit and foam at the mouth. The seizure normally lasts for less than five minutes.


When anticonvulsant therapy is judged by a doctor to be indicated, anticonvulsants can be prescribed. Sodium valproate or clonazepam are active against febrile seizures, with sodium valproate showing superiority over clonazepam.