Febrile Convulsions

Febrile seizures, or convulsions, are common (up to 5% of children age 6 months-5 years) and you will see this if you work in ED or paediatrics (1).

What is a febrile convulsion?

There are two types, simple and complex:
  • A simple febrile convulsion is a seizure occurring with a temperature of 38°C not associated with complex features and in the absence of intracranial pathology, occurring between the ages of 6 months and 5 years (2).
  • A complex febrile convulsion is with the addition of one or more of the following features:
  • >15 minutes long
    • This does not mean you should wait for 15 minutes; a generalised seizure more than 5 minutes should be treated as status epilepticus
  • Recurs within 24h
  • Focal seizure
  • Prolonged postictal drowsiness
  • Postictal palsy (Todd’s palsy)
  • Known epilepsy
  • Previous afebrile seizures or developmental anomaly

The febrile state reduces seizure threshold and, in genetically predisposed children, causes a convulsion.  They can be induced by any febrile illness, viral or bacterial, and have been reported after immunisation but this is rare (1).

Roseola infantum (HHV 6/7) is a classic cause of febrile convulsions and is characterised abrupt onset of a high fever for 3-4 days followed by a generalised maculopapular rash spreading from trunk to extremities as the fever subsides.

Differential diagnosis

Not all seizures with a fever are febrile convulsions (and did they even have a fever?)
  • Febrile convulsion
  • Intracranial infection (e.g. meningoencephalitis, subdural empyema)
  • Rigor (not a diagnosis per se)
  • Epilepsy exacerbated by fever (epileptic seizures)
  • Acute symptomatic afebrile seizure (e.g. hypoglycaemia/electrolyte disturbance, toxins, head injury)
  • Always think about NAI in a young child with new onset seizures/reduced consciousness in the absence of another clear cause
  • Other paroxysmal event
 Simple febrile convulsionMeningoencephalitisRigor
MovementGeneralised tonic‑clonic +/- eyes rolled backGeneralised or focalShaking/shivering
Length<15 mins (usually <5)Usually >5mins requiring rescueVariable
Post-eventQuick recovery (<1hr)Prolonged drowsinessNo change
Other featuresUnderlying infectionUnwell, Irritable, Vomiting, Meningism (usually absent <18 months)Underlying infection

Beware that meningoencephalitis can present with very subtle or non-specific features in young children, but progresses quickly.

History taking

Take a history of the convulsion and a full medical history

History of convulsion:

  • Before
    • What was the child doing prior to the seizure?
    • Any recent history of injury, particularly head injury.
    • Any recent fevers, coughs, colds etc? – Clarify presence of fever
    • How was the child eating and drinking prior to the convulsion? (e.g. could this have been due to hypoglycaemia)
  • During
    • What were they doing with their: eyes, face, arms, legs.
    • Was one side of their body affected or both sides?
    • Any tongue biting / incontinence?
    • How long did this last for? Did parents record a video?
    • If paramedics were called, did they give medicine to terminate the seizure?
  • After
    • Was there post-ictal drowsiness?
    • Has the child fully recovered now?
    • Are they complaining of any headaches / photophobia / neck stiffness?
  • These questions will help you differentiate a febrile convulsion from differentials and you then need to focus on finding the source of the fever
  • Febrile convulsions (after a first febrile convulsion, 30-35% of children go on to have repeated febrile convulsions with future febrile illnesses)/afebrile seizures/epilepsy
  • Recent antibiotic use (may mask meningitis)
  • Recent vaccination
  • ?any recent foreign travel
Drug history, allergies, vaccinations
Family History
  • A child is 10% more likely to have a febrile convulsion if a 1st degree family member also had febrile convulsions as a child
Social History
Growth and Development
  • Any developmental concerns or delays?
Ideas concerns and expectations


Perform a full examination, looking for neurology as well as signs of infection
  • General appearance – what are they doing? Do they look well or unwell? Are they still drowsy post-ictal? If so, how long since the convulsion? If the child appears drowsy or is showing any signs of persisting seizure activity call for help
  • Respiratory – any signs of respiratory distress? Is there a cough? Auscultate for crepitations or wheeze which may occur as a result of infection
  • Cardiovascular – Are they warm and well perfused? Check the cap refill time. If the child appears haemodynamically compromised (prolonged cap refill / tachycardic / hypotensive / mottled / cool peripherally) call for help
  • Abdominal – Is the abdomen soft and non-tender? Causes of abdominal tenderness could be appendicitis or mesenteric lymphadenitis
  • Lymph nodes – examine in the cervical and axillary chains for lymphadenopathy
  • Skin
    • Neurocutaneous stigmata. These are signs of an underlying neurocutaneous disease such as tuberous sclerosis, neurofibromatosis or Sturge‑Weber. All of these conditions are associated with seizures
    • Rashes – many childhood illnesses cause rashes, most are non-specific and benign but in a child with a high fever and no clear source you need to be sure you have properly examined for a non-blanching rash to exclude meningococcal sepsis
  • Neurological
    • DON’T EVER FORGET GLUCOSE – hypoglycaemia is a common cause of seizures and is common in itself in unwell children who are not feeding well.
    • In young children neurology can mostly be assessed by observation: AVPU, behaviour, tone, posture, balance. Also assess for irritability, photophobia, neck stiffness
    • In older child assess reflexes and examine for other signs of meningism such as Kernig’s sign
  • ENT – If you can’t find a focus for infection elsewhere, chances are it will be otitis media or tonsillitis.
    • Bear in mind that mastoiditis can track back and cause meningitis as can orbital cellulitis. Sinusitis is a cause of subdural empyema which would be on your list of differentials in a hot child with a seizure,

Red flags

Actively seek these out
  • “They’re just not right” – this might be you, the nurse, the parents or everyone.
  • See fever in under 5s NICE guideline [3]
  • No clear source (think harder – see case discussions below)
  • Focal neurological deficit
  • Prolonged drowsiness
  • Any features of a complex febrile convulsion
  • Developmental delay
  • Neurocutaneous stigmata
  • <6 months or >5 years (by definition, not a febrile convulsion and need to rethink)
  • Family history of epilepsy in first degree relative
  • Significant parental anxiety
    • This should always be considered a red flag in paediatrics and is often a reason for overnight admission.

In general, you need to be more careful with children age <18 months as the features of intracranial infection are notoriously non-specific.

So, I’ve got a well child with a typical febrile convulsion, I’m confident I have the source of the fever and that there are no red flags, what should I do?

Generally, if it is their first episode, they get referred to paediatrics for assessment but the diagnosis is clinical, and routine investigation is not necessary. Most trusts have a local guideline for febrile convulsions which you can follow

Always speak to your senior before discharging and as a general rule, a senior review for all paediatric patients before discharge is useful.

Education and safety netting is absolutely crucial:

“Does my child have epilepsy?”

Short answer: No

Long answer: Still no, but with the caveat that 5% of children with complex febrile convulsions are subsequently diagnosed with epilepsy and the more atypical features, the higher the risk. Children with simple febrile convulsions are only at very slightly increased risk of epilepsy (1%) compared to the general population (0.5%) (1,2).

Epilepsy is defined as a disease of the brain characterised by either:

  • At least two unprovoked seizures >24 hrs apart
  • One unprovoked seizure with a high probability of further
  • The diagnosis of an epilepsy syndrome.

Febrile convulsions in themselves can be recurrent but they are provoked and, by definition, are not epileptic seizures.

“What do I do if my child has another one?”

Seizures appear violent, dramatic, and are utterly terrifying to parents. They will now be worried each time their child has a fever. A third of children will go on to have at least another febrile convulsion (2).

  1. Safety net for seizure
    1. Recovery position
    1. Timer
    1. >5 mins = 999
    1. Recurrence within 24hrs = return to hospital (now a complex febrile convulsion)
  2. Safety net for underlying illness
    1. Know fever in <5s NICE guidelines (3)
    1. Use What 0-18 website endorsed by RCPCH (4)

A good leaflet goes a long way!

“Can I prevent my child from having a febrile convulsion next time?”

Antipyretics cannot prevent a febrile convulsion. Anticonvulsants can prevent febrile convulsions, but because they are considered a benign phenomenon, are not used due to the potential for significant side effects (1).

Some Case Examples Below

You are the doctor covering paeds ED tonight and the paramedics have been busy…

Read the case examples below, think of your differentials and management plan and click on the box to reveal our answers

Case 1
2-year-old girl brought in by ambulance. Dad reports she has been clingy and hot today. This evening while on the sofa she became unresponsive and started jerking all her limbs for 1-2 minutes. She is normally fit and well, developing normally. 20 minutes later in the emergency department she is fully alert. She is clingy but watching videos with her dad. She has a high temperature, a very snotty nose, and a red throat but her examination is otherwise normal. After some paracetamol she perks up, drinks some juice and is playing with some toys.

This meets the definition of a simple febrile convulsion in a well child with no red flags.

Educate, reassure, safety net.  

Case 2
18-month-old boy brought in by ambulance. He was sent home from nursery with a fever and this evening while watching TV became unresponsive and started jerking the right side of his body for 1-2 minutes. 20 minutes later in the emergency department he is fully alert and playing with his toys. He is rather snotty with a red throat.

As you now know, this is a complex febrile convulsion.

He will need further assessment. Be very careful with children who have febrile seizures that are either focal, prolonged, or are recurring within the same illness. These can be features of an intracranial infection such as encephalitis. 

Case 3
2-year-old girl brought in by ambulance. She became unresponsive and started jerking all four limbs while watching a movie. Mum thinks it probably only lasted a minute or so and is worried because she felt like she was “burning up.” She is normally fit and well, developing normally. 20 minutes later in the emergency department she is fully alert but clingy. She has a high temperature but her examination is otherwise completely unremarkable. After some paracetamol she perks up, drinks some juice and is playing with some toys.

This is a simple feb con but what is the source!?

A fever without an apparent source may be due to one of three reasons:

  • A) it is too early in the illness to tell – it may be a serious illness or not
  • B) it is a non-specific but serious illness (you would be surprised at how few clinical signs children with pneumonia can have, for example)
  • C) you have not looked hard enough for a source (e.g., get a urine)

The key bit of information in our case is that the child looks well, so the likelihood of this being a serious illness is currently low.

At a minimum, these children should have a period of observation (usually referred to paediatrics) – time during which you demonstrate the child is stable, or where the serious illness starts to declare itself.

Case 4

3-year-old boy brought in by ambulance. Mum reports he has not been himself today. This evening, just after being put down for an early bedtime, started jerking the left side of his body for several minutes. 40 minutes later in the emergency department he remains drowsy and difficult to rouse. He has a high temperature, a snotty nose, and a red left tympanic membrane.

This is meningoencephalitis until proven otherwise. A very snotty nose and a red ear is indeed a source of infection but a simple viral URTI or acute otitis media cannot fully explain this presentation. Most children are snotty most of the year, especially during Winter so it may be a coincidence. Alternatively, intracranial infections can complicate ear infections.

Case 5
2-year-old girl brought in by ambulance. Her dad tells you that while fetching her a thermometer and paracetamol, he found her unresponsive and jerking all four limbs, stopping just as the paramedics arrived. She has a history of febrile convulsions but is otherwise fit and well. You notice she does not yet say any words. On examination, she is miserable and snotty but perks up after her temperature comes down and looks well.

She has had a febrile convulsion, is well, and has a source of infection. A 2-year-old, however, should be able to speak.

Developmental delay is a red flag and she needs further evaluation – this may be unrelated, or be secondary to an epilepsy syndrome, for example.

Summary and final thoughts

Simple febrile convulsions are common and benign. Rule out serious pathology, find and treat the source of the fever, and then educate, reassure, and safety net. Make sure to document what you have said/given to parents.

As for all paediatric presentations, always seek senior input from the registrar or consultant. Sometimes, things are not evident at first assessment and things can change rapidly in children which is why a period of observation can be so useful.

Further reading and references

  1. Leung AK, Hon KL, Leung TN. Febrile seizures: an overview. Drugs Context. 2018; 7:212536. Doi: 10.7573/dic.212536
  2. Capovilla G, Mastrangelo M, Romeo A, Videvano F. Recommendations for the management of “febrile seizures” Ad hoc Task Force of LICE Guidelines Commission. Epilepsia. 2009; 50(1): 2-6. Doi: 10.1111/j.1528-1167.2008.01963.x
  3. National Institute for Health and Care Excellence. Fever in under 5s: assessment and initial management. https://www.nice.org.uk/guidance/ng143
  4. Healthier Together. Febrile Convulsion advice intended for parents/carers taking their child home after seeing a doctor. https://www.what0-18.nhs.uk/professionals/gp-primary-care-staff/safety-netting-documents-parents/febrile-convulsion

Written by Dr George Aldersley Paediatrics ST2

Edited by Dr Rebecca Evans Paediatrics ST3

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1 thought on “Febrile Convulsions”

  1. Dr James Mackintosh

    The case reports are really helpful in showing how to apply the knowledge in my clinical practice in the emergency department.

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