Febrile Convulsions

The Clinical Knowledge Summaries (previously Prodigy guidelines) from 2005 give a definition that, "A febrile convulsion is a seizure occurring in a child aged 6 months to 5 years, associated with fever arising from infection or inflammation outside the central nervous system in a child who is otherwise neurologically normal." This definition excludes meningitis, encephalitis and epilepsy.

There is little evidence indicating whether the degree of fever or the rate of rise are more important triggers in febrile convulsions. They are commonly associated with viral infections. There is no consensus about what level of temperature should be the threshold for the diagnosis but the diagnosis should be made "if the history and examination are indicative." It may even be that the temperature is irrelevant and that convulsions are caused by the release of cytokines that are also the cause of the temperature.¹

• Between 2 and 4% of children will have a febrile convulsion
• About 4% of cases arise before 6 months old, 90% between 6 months and 3 years and the other 6% over 3 years.²
• Febrile convulsions may occur over the age of 5 but this is most unusual.
• 30% will have another febrile convulsion but less than 10% have more than 3.
• They are more likely to occur if there is a family history of febrile convulsions or epilepsy.

Diseases that lead to convulsions are, in descending order of frequency:³

• Viral infections
• Otitis media
• Tonsillitis
• Urinary tract infection
• Gastroenteritis
• Lower respiratory tract infection
• Meningitis (strictly speaking this is not a febrile convulsion as it involves the CNS but it has to be part of the differential diagnosis)
• After immunization

• The child who has a first convulsion will be between 6 months and 3 years in 90% of cases.
• The convulsion tends to occur early in the illness.
• Ask about other illness. There may be an obvious viral illness causing the temperature or a cold predisposing to otitis media. There may have been recent immunization
• The convulsions are usually general tonic clonic and at the time of high temperature.
• There should be full recovery within an hour.

Convulsions may be classified as simple, complex or febrile status epilepticus:

• Simple febrile convulsions - isolated, generalized, tonic-clonic seizures lasting less than 10 to 15 minutes.
• Complex febrile convulsions -
  • Last between 15 and 30 minutes
  • Or are focal
  • Or recur during the febrile illness
  • Or are not followed by full consciousness within an hour.
• Febrile status epilepticus - single or recurrent seizures lasting ≥30 minutes, without recovery of full consciousness between convulsions.

Examination

Note the level of consciouness. Beware the child who is slow to recover.

Clinical examination may reveal the source of infection such as otitis media. Less than 10% have bacterial meningitis but it must not be missed. In small children signs of meningism may be absent.

The petechial rash of the meningococcus should be looked for but it does not occur in other forms of meningitis. It really it indicates septicaemia rather than meningitis so it can be absent, even in meningococcal meningitis. Hence, if present, it means meningococcal infection. If absent, it signifies nothing.

• Try to make a diagnosis and, in particular, decide if this is a child who can be managed at home or who requires admission. Make the latter decision with the parents, being happy to admit if they are anxious.
• Use paracetamol or ibuprofen in appropriate dose to bring down the temperature. Making sure that the child is not wrapped up is sensible. Tepid sponging does appear to work but the evidence is not spectacular.⁴ The importance of treating the fever is not as great as has been traditionally taught.¹
• If it is a simple febrile convulsion, reassure the parents about the benign nature, including the very low risk of subsequent epilepsy. A child having a fit is a very worrying and upsetting sight for parents.
• Teach parents to manage a recurrent convulsion with such matters as the recovery position and not forcing anything into the mouth.
• Whether or not the convulsion is thought to be due to immunization, advise the parents that immunization schedules should be completed as planned.
• Admit if indicated. Otherwise arrange early review. Tell the parents that if anything changes and if they are worried at all they are free to call again.

Whom to admit?

The Clinical Knowledge Summaries guidance says,"Most children with a first febrile convulsion do not need to be admitted (to hospital). The main concern is the possibility of missing a more serious diagnosis such as meningitis." Nevertheless, many GPs may be rather more wary. Those with complex convulsions are more likely to have a serious disease. Less than 10% will have bacterial meningitis but that is not a diagnosis to be missed as it is treatable and early treatment may have a substantial effect on the outcome. Children change quickly and if there is reason to believe that circumstances have changed, do not be afraid to admit.

Management in secondary care

In secondary care, the patient may be seen after the convulsions have stopped and the question arises of whom to admit. The above criteria are still useful. There are a number of other points:

• The major concern is missing a diagnosis of meningitis.
• Check capillary blood sugar if the child is still convulsing or not fully alert.
• Lumbar puncture should always be performed unless contraindicated where there are definite signs of meningitis such as petechiae or nuchal rigidity but start antibiotics first.
• If the child is comatose, there may be a need for CT before LP.
• After a complex convulsion or febrile status epilepticus
• If the child is unduly drowsy or irritable or systemically ill.
• It is also recommended in cases where meningitis is more likely, including:
  • 3 days of illness
  • Seen a GP in last 24 hours
  • Drowsiness or vomiting at home
  • Possible nuchal rigidity, convulsing when examined, weakness on examination, headache
  • Prior (partial) treatment by antibiotics
• Be more inclined to admit children aged under 12 months
• Children with simple febrile convulsions who have no suggestion of possible meningitis, who continue to look well, and have no focus of infection may then be discharged home provided that there is ready access to health care if required, and parents are happy with the decision. Check the urine first, as a possible source of infection. No further investigation is usually indicated in such patients, particularly if the cause of fever is identified clinically and the cause does not require further investigation.
• Give parents an information leaflet

Lumbar puncture

• LP is not necessary in all cases of simple febrile convulsion but a LP should always be performed if the child is less than 18 months old as there may be none of the typical signs of meningitis.
• Lumbar puncture is contraindicated if there is raised intracranial presure because of the risk of coning. Such features include:
  • If there are signs of septic shock
  • A clinical diagnosis of invasive meningitis with a haemorrhagic rash
  • There are focal neurological signs
• In such cases, antibiotics should be given immediately and an urgent CT scan performed. The LP can be performed if the CT suggests that pressure is not raised.
• Children who are admitted but do not require a LP should be observed closely and reviewed within two hours. In particular, observe children who have had previous antibiotic treatment as signs of meningitis may be less evident.

Most children who have had a febrile convulsion make an uneventful recovery with no long term sequelae. There is no impairment of intellect or behaviour.⁷Only 1% of children who have had a febrile convulsion go on to develop epilepsy compared with 0.4% who have not. This probably represents a lower threshold to fit rather than a causative effect.
Risk factors for recurrence include:

• The first febrile convulsion was before the age of 15 months.
• The first convulsion is complex.
• There is a family history of febrile convulsions or epilepsy in a first-degree relative.
• The child attends day nursery. This is simply because of increased risk of getting a febrile illnesses.

If there are none of these risk factors the risk of recurrence is 10%. With 1 factor it is 25%. With 2 factors it is 50% and with 3 or all 4, the chance of recurrence is almost 100%.⁸
If the convulsion followed an immunization it is not likely to follow subsequent immunizations.⁹
Both diazepam and phenobarbital may reduce the risk of recurrent seizures but the side effects are such that they cannot be recommended.¹⁰