Febrile Convulsions

oPatientPlus articles are written by UK doctors and are based on research evidence, UK and European Guidelines. They are designed for health professionals to use, so you may find the language more technical than the condition leaflets.

Synonyms: febrile seizure, febrile fit

Febrile convulsions are seizures (fits or convulsions) occurring in children aged 6 months to 5 years, associated with fever, without other underlying cause such as CNS infection or electrolyte imbalance.[1]

Consensus guidelines agree that:[2]

  • Axillary temperature should be >37.8°C (or)
  • There is a clinical history and examination indicative of febrile seizure.
  • If the child is still convulsing or not fully alert:
    • Recovery position, check and maintain Airway, Breathing, Circulation.
    • Check blood glucose.
    • Give an antipyretic if feasible (although there is no clear evidence that this prevents seizures).
    • If seizing >5 minutes, give rectal diazepam (this may be repeated after 5 minutes if the seizure has not stopped), OR a single dose of buccal midazolam (off-licence use).
  • Benzylpenicillin or cefotaxime if meningococcal disease is suspected:
    • Suspect meningitis in any child who is systemically unwell, irritable, or who was drowsy before the seizure.
    • Important signs are: neck stiffness; petechial rash, photophobia; Kernig's sign; Brudzinski's sign; bulging fontanelle; reduced level of consciousness.
  • Call 999 ambulance/senior help if: the seizure lasts >10 minutes (this includes ongoing twitching even if large jerking movements have stopped, OR a further seizure before the child recovers consciousness); OR serious illness is suspected.

Simple febrile seizures

These are generalised, tonic-clonic seizures lasting less than 15 minutes, that do not recur within 24 hours or within the same febrile illness.

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Complex febrile seizures

These have one or more of the following:

  • Focal features at onset or during the seizure.
  • Duration of more than 15 minutes.
  • Recurrence within 24 hours, or within the same febrile illness.
  • Incomplete recovery within 1 hour.

Febrile status epilepticus

This is a febrile seizure lasting for longer than 30 minutes.

NB: other types of seizure related to acute illness in children are:[1]

  • Febrile myoclonic seizures.[4]
  • Afebrile convulsions in young children with mild gastroenteritis - clusters of seizures with/without fever over several days, in the setting of gastroenteritis. The prognosis is good.
  • Between 2% and 4% of European children have a febrile convulsion; the peak incidence is age 18 months.
  • Most are the simple febrile seizure type. Complex febrile seizures occur in about 20% and febrile status epilepticus in about 5%.

The mechanisms are unknown. It is uncertain whether the degree of fever or the rate of rise of temperature are triggers in febrile seizures.

Genetic factors are involved: there is a family history of febrile seizures in 24%. Inheritance patterns are probably polygenic, although in a few families a particular gene or autosomal dominant inheritance has been identified.

Causes of fever in children with febrile seizures

The vast majority are:

Other causes of fever with seizure are:

  • Gastroenteritis
  • Post-immunisation
Serious illnesses which need excluding are:
  • History - including:
    • Eye witness account of the seizure: conscious level prior to seizure, duration, focal or generalised, time taken to recover and state of the child afterwards.
    • Symptoms of meningitis or septicaemia, such as: rapid onset of illness, abnormal behaviour or cry, stiffness or floppiness, vomiting, (and meningism in older children). Early symptoms are: leg pains, cold hands and feet, pallor or mottled skin.[5]
    • Was it a febrile seizure? This may be difficult to decide if the seizure occurs early in the illness. Parental perceptions of fever are valid.
    • Past/family history of febrile seizure or epilepsy.
  • Examination:
    • Vital signs, conscious level, rash (blanching or non-blanching), fontanelle, meningism.
    • Look for focus of infection.

Note that:

  • For babies and young children, clinical examination (more than history) is important in detecting serious illness. The vital signs are informative (temperature, pulse rate, respiratory rate and effort, capillary perfusion and oxygen saturation - compare with the normal range for the child's age).[6]
  • The National Institute for Health and Clinical Excellence (NICE) traffic light system can help assess the likelihood of serious illness in a child with fever.[7] 
  • First febrile seizure.
  • Serious illness not excluded.
  • Previous history of febrile seizure with:
    • Child <18 months of age (meningitis is harder to detect in this age group).
    • Diagnostic uncertainty about the cause of the present seizure.
    • A complex seizure (as defined above - these are more likely to recur or be due to intracranial infection compared with simple seizures).
    • Antibiotics taken currently/recently (in case these mask signs of meningitis).
    • Early review by a doctor is not possible.
    • Home circumstances are unsuitable.
  • Also, consider referral if no focus of infection is found (for a period of observation and to investigate for UTI).

Paediatric assessment[2]

  • Admit and treat as meningitis if there are any alarming features:
    • Drowsy before seizure or Glasgow Coma Scale (GCS) <15 at 1 hour after seizure.
    • Neck stiffness.
    • Petechial (non-blanching) rash.
    • Bulging fontanelle.
  • Admit and review (review within 2 hours by paediatric registrar, to consider lumbar puncture (LP)), if:
    • Under the age of 18 months.
    • Complex seizure.
    • The child has had antibiotics.
    • Consider admission if no focus of infection is found.
  • Other children may go home if child well, parents agree and able to manage child at home, and can promptly access medical care. (See 'Advice for parents', below).

Initial investigations are according to the febrile illness rather than the seizure itself. These may include:

  • Blood tests: FBC, erythrocyte sedimentation rate (ESR), glucose, U&E, coagulation, culture.
  • Urine microscopy/culture if: age <18 months, complex seizure or no focus of infection found.
  • Lumbar puncture (LP) should be considered for:
    • A child <12 months - LP advised unless a paediatric registrar decides against LP and will review within 2 hours.
    • A child 12-18 months - has a low threshold for LP.
    • Any 'serious features' (see details relating to hospital assessment above).

NB: contra-indications to LP:

  • Reduced consciousness (GCS <13 or falling consciousness level).
  • Septicaemic shock (poor perfusion, tachycardia, low BP).
  • Likely invasive meningococcal disease (rapid onset of illness, haemorrhagic rash).
  • Signs of raised intracranial pressure (coma, abnormal posture or pupils, high BP, low pulse, papilloedema).
  • Focal neurology.
  • Bleeding tendency - known or clinically suspected.
  • Rigors.
  • Syncope.
  • Breath-holding spells.
  • Reflex anoxic seizures - a precipitant (eg a minor bump) causes vagally-mediated cardiac asystole lasting many seconds - the child may be pale, floppy, and lose consciousness, followed by tonic and clonic movements.
  • Apnoea.
  • Post-ictal fever (unlikely unless the seizure lasted >10 minutes; usually they would have a temperature >38°C).
  • Other cause of seizures, eg epilepsy, head injury, encephalitis, hypoglycaemia, hypocalcaemia, poisoning, other metabolic disorders, neurological disorders.
  • Afebrile seizures with gastroenteritis[1] (see above).

Children may be managed at home if:

  • The child looks well.
  • Parents understand how to treat febrile illness and further seizures, have prompt access to medical care and are happy with this plan (see 'Advice for parents', below).
  • Arrange review; the timing depends on clinical condition - early review advisable if the cause of fever is unclear.

Remember:

  • Review the child and address the parents' questions.
  • Consider outpatient referral if:
    • An alternative cause for seizures is suspected, eg epilepsy or a neurodevelopmental condition.
    • Prophylaxis with anticonvulsants is being considered (see directly below).
    • Parental request or concerns.
  • Prophylaxis of febrile seizures may be considered for situations such as prolonged seizures or for children who have a low threshold for seizures, especially if the family lives far from medical help.
    • Diazepam given during a fever may reduce recurrence of febrile seizures.
    • There is probably no benefit from anti-epileptic drugs in this scenario.

Explanation is important, as seizures can be very frightening for parents. The following points should be covered and a leaflet provided:

  • What febrile seizures are.
  • How to treat fever at home - remove excess clothing, give fluids, give antipyretics if the child is uncomfortable. Tepid sponging or excessive cooling are not recommended. Check for a non-blanching rash, check for dehydration, and stay with the child at night.
  • First aid if the child has a fit - position; do not put anything in their mouth.
  • When to call 999 ambulance - a seizure lasting more than 5 minutes.
  • When and how to seek urgent medical advice - any seizure, serious symptoms such as non-blanching rash, lack of normal alertness, dehydration, the child getting worse, the parent worried, and fever >5 days.

Generally the prognosis is good:

  • By definition, febrile seizures do not recur beyond the age of 5 years approximately.
  • There is no evidence for an increased risk of death, even for children with status epilepticus.[3]
  • Intellect is not affected.
  • Febrile seizures recur in about 30%. Risk factors for recurrence are: family history of febrile seizures, onset aged <18 months, lower temperature or shorter duration of fever at onset.
  • Risk of epilepsy:
    • The chance of developing epilepsy increases with certain features, which include: complex febrile seizure, other neurological abnormality, family history of epilepsy, and fever <1 hour before the seizure.
    • Without these features, 2.4 % of children with febrile seizures develop epilepsy (compared with 1.4% for the general population).
  • Immunisations do not appear to increase the risk of recurrent febrile seizures.
  • There is no evidence that antipyretics reduce the number of febrile seizures.
  • Diazepam (oral and rectal) at relatively high doses may prevent febrile seizures if given at the onset of a febrile illness. However, adverse effects such as ataxia, lethargy and irritability could make it harder to distinguish between benign and serious illness.
  • Anti-epileptic drugs such as phenobarbital have some effect in preventing febrile seizures (number needed to treat to prevent one febrile seizure = 8 children for 2 years), but adverse effects outweigh benefits.

Further reading & references

  1. Sadleir LG, Scheffer IE; Febrile seizures. BMJ. 2007 Feb 10;334(7588):307-11.
  2. 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; 20:13-20
  3. Febrile seizure; NICE CKS, June 2008
  4. Dooley JM, Hayden JD; Benign febrile myoclonus in childhood. Can J Neurol Sci. 2004 Nov;31(4):504-5.
  5. Thompson MJ, Ninis N, Perera R, et al; Clinical recognition of meningococcal disease in children and adolescents. Lancet. 2006 Feb 4;367(9508):397-403.
  6. Davies F; Paediatric health: Recognising the sick child, Electronic Doctor
  7. Feverish illness in children - Assessment and initial management in children younger than 5 years; NICE Guideline (May 2013)

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.

Original Author:
Dr Huw Thomas
Current Version:
Peer Reviewer:
Dr Huw Thomas
Last Checked:
11/06/2013
Document ID:
1149 (v26)
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