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Febrile seizure

A febrile seizure, also known as a fever fit or febrile convulsion is a generalized convulsion caused by elevated body temperature. They most commonly occur in children below the age of three years old and should not be diagnosed in children under the age of 6 months or over the age of 6 years. In many cases, the first sign of fever is the onset of the seizure. It has been theorized that the seizure is triggered by the rapidity of the rise in temperature, rather than the actual temperature reached. more...

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Febrile seizures represent the meeting point between a low seizure threshold (genetically and age determined) - some children have a greater tendency to have a seizure under certain circumstances - and a trigger: 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: in particular, meningitis and encephalitis must be ruled out. Therefore a doctor's opinon 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 it is unlikely. Even in cases where the diagnosis is febrile seizure, doctors will try to identify and treat the source of fever. In particular, it is useful to distinguish the event as a simple febrile seizure - in which the seizure lasts less than 15 minutes, does not recur in the next 24 hours, and involves the entire body. The complex febrile seizure is characterized by long 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. It is reassuring if the cause of seizure can indeed be determined to have been fever, as simple febrile seizures generally do not cause permanent brain injury; do not tend to recur frequently, as children tend to 'out-grow' them; and do not make the development of adult epilepsy significantly more likely.

Children with febrile convulsions who are destined to suffer from afebrile epileptic attacks in the future will usually exhibit the following:

  • A family history of afebrile convulsions in first degree relatives (a parent or sibling)
  • A pre-convulsion history of abnormal neurological signs or developmental delay
  • A febrile convulsion lasting longer than 15 minutes
  • A febrile convulsion with strong indications of focal features before, during or afterward


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Approach to young children with febrile seizures - Tips from other journals - Author Abstract
From American Family Physician, 9/15/03 by Richard Sadovsky

The majority of seizures in children younger than five years are febrile seizures, and children with a positive family history have a higher incidence. A febrile seizure is defined as any seizure occurring in a child who is six months to five years of age accompanied by a current or recent fever (at least 38[degrees]C [100.4[degrees]F]) and without previous seizure or neurologic events. Febrile seizures can be classified as simple or complex. Simple febrile seizures are characteristically generalized, usually last less than 15 minutes, and occur only once in a 24-hour period. Complex febrile seizures may have focal features, last longer than 15 minutes, and recur within a 24-hour period. Fever and seizure can occur at the same time and be unrelated, such as in patients with underlying seizure disorder, patients who are out of the febrile seizure age range, or patients who have a central nervous system infection.

Warden and associates searched the clinical literature to review the evaluation and management of febrile seizures in children. Viral infections are often present with febrile seizures, with human herpes virus 6 and 7 and influenza A and B being important pathogens. There also is a significant increased risk of febrile seizures within 24 hours of receiving vaccination for diphtheria and tetanus toxoids and whole-cell pertussis, and within eight to 14 days of receiving a measles, mumps, and rubella vaccination. The risk of recurrent febrile seizures is increased in patients whose initial febrile seizure occurred at less than 12 months of age, patients with a lower rectal temperature at first seizure (less than 40[degrees]C [104[degrees]F]), patients with shorter duration of fever before their first seizure (less than 24 hours), patients with a family history of febrile seizures, and patients with complex features with the first febrile seizure. The risk of development of epilepsy is slightly increased among persons having simple febrile seizures but is significantly increased among those who have one or more complex febrile seizures.

Initial evaluation of children with febrile seizure includes airway and circulatory support, ideally with noninvasive measures until the postictal state resolves. Patients are best evaluated in the hospital setting. A thorough medical history that includes past seizures and other neurologic conditions, exposure to medications or toxins, allergies, or trauma may point to a specific seizure cause. Treatment with antipyretics is rarely necessary in the typical seizure case. Patients with seizures that last longer than five minutes should receive a benzodiazepine. After the seizure ends, the physician should conduct a mental status examination and a physical evaluation. Routine laboratory studies include only a blood glucose test; an electrolyte test may be appropriate if a metabolic abnormality is being considered. No further work-up is necessary, but lumbar puncture is indicated in patients with suspected meningitis.

A lumbar puncture should be considered in children younger than 18 months who have a febrile seizure with the following: (1) a history of irritability, decreased feeding, or lethargy; (2) an abnormal appearance or mental state on initial observation after the postictal period; (3) any physical examination evidence of meningitis; (4) any complex features; (5) any slow postictal clearing of mentation; or (6) pretreatment with antibiotics. Neuroimaging only is appropriate in patients at risk of cerebral abscess, in those who have clinical evidence of increased intracranial pressure, in patients who have evidence of trauma, or in patients who have status epilepticus or have had a complex seizure. Children with simple febrile seizures can be cared for at home after providing parental education and making plans to follow up with the family.

The authors conclude that evaluation and management of simple febrile seizures can be managed in an outpatient emergency setting and the child can be sent home for further care (see accompanying table). Children with complex seizures might require hospitalization for evaluation. Routine prophylaxis using phenobarbital, valproic acid, oral diazepam, or antipyretics is controversial and not indicated.

Evaluation and Management of Simple Febrile Seizures

History and physical examination

Blood glucose testing

Supportive care

Treatment of any infectious causes

Reassurance and anticipatory guidance to parents

Warden CR, et al. Evaluation and management of febrile seizures in the out-of-hospital and emergency department settings. Ann Emerg Med February 2003;41:215-22.

COPYRIGHT 2003 American Academy of Family Physicians
COPYRIGHT 2003 Gale Group

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