The treatment of febrile convulsions

The basics
Dr Laurence Knott outlines how to diagnose and treat febrile convulsions.

Febrile convulsions are seizures associated with a high temperature, precipitated by an infection arising outside the nervous system, in a child who is otherwise neurologically normal.

They are rare before six months and after five years, and are most common between 18 months and three years. Three in 100 children have a febrile convulsion before they are six.

Boys are more prone to febrile convulsions than girls, and a positive family history is common. They can be associated with any illness that causes a high temperature, commonly ear infections, coughs, colds and flu. Strangely, they are rarely seen in more serious diseases such as pneumonia. They are rarely precipitated by rectal temperatures below 38degC.

There are two types of convulsion. Simple febrile convulsions are generalised, isolated tonic-clonic seizures lasting 10-15 minutes. Complex febrile convulsions can last 15-30 minutes, may be focal, may recur during the febrile illness, or may not be followed by full consciousness within an hour.

Diagnosis
Check with the child's parents or the records that the child has no previous history of neurological problems.

Examination should include a search for a focus of infection. Check for signs of bacterial meningitis such as fluctuating consciousness, pale blotchy skin or a petechial rash, cold hands and feet, photophobia and Kernig's and Brudzinski's signs.

Investigations would be used to identify a covert infection, but if there is the slightest doubt as to the cause, the safest counsel is to refer the patient to hospital.

Management
Consider hospital referral if the child is under 18 months; if there is complex convulsion or febrile status epilepticus - single or recurrent seizures lasting more than 30 minutes without recovery of consciousness between seizures; if there is no obvious focus of infection; if there are signs of meningism; if there is inadequate community support; or if the underlying infection focus needs hospital treatment.

Other patients can be managed in the community in the first instance.

Most seizures will resolve spontaneously.

There is no evidence that aggressive cooling helps to reduce risk. If the child is still fitting at the time of presentation, this can be curtailed with rectal diazepam.

Rectal diazepam may be given at the onset of fever to prevent future convulsions in children at high risk of recurrence of severe or complex seizures.

Anticonvulsants such as phenobarbital were used to prevent febrile convulsions, but studies suggest that the adverse effects outweigh their benefits.

One in three children who have one convulsion will have another; but there are rarely any long-term sequelae in terms of damage to the nervous system.

Dr Knott is a GP in Enfield

Differential Diagnosis

Any other cause of convulsion with or without fever, for example:

  • Meningitis (0.6-6.7 per cent of children presenting with 'febrile convulsions').
  • Encephalitis.
  • Epilepsy.
  • Cerebral palsy with intercurrent infection.
  • Hypoglycaemia or other metabolic disorder.
  • Neurodegenerative disorders.
  • Shaking injury.

Learning points

  • Febrile convulsions are often associated with ear and chest infections.
  • Bacterial meningitis must be ruled out.
  • Consider referring children who are under 18 months, have a seizure of more than 30 minutes or have no obvious site of infection.
  • Rectal diazepam solution can end a seizure.
  • Anticonvulsants should not be given routinely.

References

Offringa M, Moyer V A. Evidence-based paediatrics: evidence-based management of seizures associated with fever. BMJ 2001; 323: 1,111-4.

Armon K, Stephenson T, MacFaul R et al. An evidence- and consensus-based guideline for the management of a child after a seizure. Emerg Med J 2003; 20(1): 13-20.

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