Clinical Review - Febrile seizures

Contributed by Dr Kathryn Deakin, consultant paediatrician, Pinderfields General Hospital, Wakefield, West Yorkshire

The majority of febrile seizures occur on the first day of onset of fever (Photograph: Carolyn A. McKeone / Science Photo Library)
The majority of febrile seizures occur on the first day of onset of fever (Photograph: Carolyn A. McKeone / Science Photo Library)

Section 1: Epidemiology and aetiology
Febrile seizures - also known as febrile convulsions - occur in children aged between six months and five years, and are associated with fever arising from infection or inflammation outside the CNS in a child who is otherwise neurologically normal. These age limits are arbitrary and should only be used as a guide.

Although febrile seizures were first described by the Ancient Greeks, it was not until this century that they were first considered to be a distinct syndrome. They are now recognised as the most common seizure disorder in childhood, affecting 2-5 per cent, with a peak incidence at 18 months of age.1

The majority of febrile seizures will occur before the age of three years, with only 6-15 per cent occurring after four years of age. There is a slight predominance in boys of 60 per cent.

Classification
Febrile seizures are broadly divided into two types: simple and complex. Simple febrile seizures are generalised tonic-clonic seizures, which last less than 15 minutes (usually three to six minutes), resolve spontaneously and do not recur within 24 hours. Complex febrile seizures are focal, last longer than 15 minutes and occur more than once in 24 hours.2 Approximately 70-75 per cent of febrile seizures are simple.1

Aetiology
The majority of febrile seizures (78 per cent) will occur on the first day of the onset of fever and may be the presenting feature of an infection. Within the course of the fever, it is difficult to determine the exact mechanism that ultimately leads to a seizure. Most data supports the hypothesis that the brains of children under five years have an increased sensitivity to fever, provoking excitability of their CNS, leading to a seizure.1 There is no data to support that the rate of temperature rise is more important than the peak temperature achieved.3

It is unclear whether there is a lower limit of fever under which a diagnosis of febrile seizure should not be made, however children with febrile seizures at relatively low temperatures (less than 38.9° tend to present with complex rather than simple seizures.3

Research has shown that antipyretics do not reduce the risk of febrile seizures. This has led to the suggestion that it is not the fever itself which causes the seizures. Preliminary studies suggest that infection causes activation of the cytokine network, which causes the fever and seizure activity in the developing brain.4

Section 2: Making the diagnosis
Seizures of any type are usually a manifestation of a number of underlying pathologies. Other events which may mimic a febrile seizure include rigors, syncope, reflexic anoxic seizures, breath-holding spells and apnoea; a careful history will differentiate these.

Clear evidence exists to suggest a genetic susceptibility for febrile seizures, although the mode of inheritance is still unclear. In a child with febrile seizures, the risk of a sibling developing them is 10 per cent, this will increase to 50 per cent if either parent also has a history of febrile seizures,1 and vastly increases if both parents has a past history.

A family history in first degree relatives is the most consistent predictor of developing febrile seizures and recurrent seizures, with the more relatives affected the greater the risk. The risk is increased by having an underlying brain disorder, having had a delayed neonatal discharge of more than 28 days or going to day care where children pick up more infectious diseases.1 There is also thought to be a link between febrile seizures and exposure to infectious illnesses such as herpesvirus-6 (roseola infantum) or influenza A2.

Any viral or bacterial illnesses which cause fevers can provoke febrile seizures, and this is also true - although rarely seen - for immunisations, with diphtheria, tetanus, and pertussis and MMR causing the highest risks.5 It is however important to remember that past history or a family history of febrile seizures is not a contraindication to immunisation. At least 50 per cent of all children presenting with febrile seizures will have no identified risk factors.1

CONDITIONS ASSOCIATED WITH FEBRILE SEIZURES
  • Viral infection
  • Otitis media
  • Tonsillitis
  • UTI
  • Gastroenteritis
  • Lower respiratory tract infection
  • Meningitis
  • Post-immunisation

Serious causes
The main concern in general practice is missing a more serious diagnosis such as meningitis in a child who has had a febrile seizure. The estimated incidence of meningitis in children who present with a febrile seizure is 2-5 per cent.6 Complex febrile seizures are more likely to be provoked by serious infections than simple ones.

Post-ictal symptoms other than drowsiness are rare, and should raise the suspicion of another diagnosis or a more serious cause.

Children under the age of 12 months should have a lumbar puncture, especially after their first febrile seizure, if there are difficulties in diagnosing the focus of infection.

Investigations
Investigations should aim to identify the cause of the fever. In the majority of children, a blood glucose to rule out hypoglycaemia and a urine culture will be the only investigations needed.1 Viral illnesses and otitis media are the most common sources of fever in children with febrile seizures.5 The box shows the conditions usually associated with febrile seizures in decreasing order of frequency.

Neuroimaging and EEGs have been found to be of limited value in diagnosis or in predicting future seizures.

Neuroimaging and EEGs are of limited value in diagnosis (Photogaraph:
AJ Photo / Hop American / Science Photo Library)

Section 3: Managing the condition
Despite the frequency of febrile seizures, there is still some disagreement about treatment. Watching a child having a febrile seizure can be extremely frightening for parents and some parents often report that they thought the child was dying.

Fortunately the vast majority of febrile seizures are benign, with no documented cases of related deaths.6 Furthermore there is no proven link between febrile seizures and sudden infant death syndrome.7 Healthcare professionals should understand the potential misconceptions, anxieties and fears parents have in order to reassure them.

Hospital admission
Most children, especially those who have had a simple febrile seizure, do not need to be admitted to hospital.

Admission should be considered if:

  • it is the first febrile seizure.
  • the child is under 18 months of age.
  • there are signs of meningitis: drowsiness, irritability, photophobia, headache.
  • the child was systemically unwell prior to the seizure.
  • there is a non-blanching rash.
  • the seizure is complex.
  • there is no possibility of early review by a doctor.
  • there are inadequate home circumstances or social concerns.
  • the parents cannot be reassured.
  • the cause of the fever requires hospital investigation and management.
IMPORTANT POINTS IN FURTHER MANAGEMENT
  • Reassure parents that febrile convulsions do not harm children.
  • Give parents advice on controlling fever in the future with the use of antipyretics and cool clothing.
  • Advise parents on the management of recurrent convulsions: recovery position, safety.
  • Admit to hospital if the child needs observation, investigation or treatment for the cause of fever.
  • Recommend completion of the immunisation schedule.
  • Discuss future risks of recurrence and developing epilepsy.
  • Seek specialist advice regarding medication in prolonged, frequent seizures or atypical febrile seizures.

Management
Treatment should be aimed at trying to control the fever and treating the underlying cause. High fevers are best reduced by giving paracetamol and ibuprofen and removing excess clothing. Fanning and tepid sponging may only have a short-term benefit in bringing fevers down, and may just upset the child.

The main aim of management is education and reassurance of the parents, which includes giving written information tailored to the patient's language and culture.

At the time of seizures, parents should be advised to:

  • stay calm.
  • place the child in the recovery position on a protected surface.
  • clear the area around them.
  • do not hold the child's head.
  • do not put anything in their mouth.
  • time the seizure.
  • if it lasts more than a few minutes call NHS Direct or your GP.
  • if it is prolonged dial 999 and request an ambulance.

Literature reviews have looked into the prophylactic treatment of febrile seizures, and have concluded that although there is evidence that continuous treatment with antiepileptic drugs can be effective in reducing the recurrence of febrile seizures, the potential toxicities associated with these drugs outweigh the relatively minor risks associated with the seizures.8,9

Children who have troublesome seizures or who have parents with high levels of anxiety may be treated with oral diazepam. Although this may reduce the risk of further seizure it can cause ataxia, lethargy and irritability and therefore should only be prescribed after specialist assessment.

Advise parents to place the child in the recovery position and clear the
area around them (Photograph: Faye Norman / Science Photo Library)

Section 4: Prognosis
The main concern most parents have is whether their child is at increased risk of developing epilepsy. They can be reassured that those with simple febrile seizures have approximately the same risk of developing epilepsy by the age of seven as the general population (1 per cent chance).

This risk increases in children who have had multiple febrile seizures, are less than 12 months of age at the time of their first seizure, have a family history of epilepsy, or have had complex febrile seizures. In this group, 2.4 per cent will develop afebrile seizures by the time they are 25 years old.

The recurrence risk of simple febrile seizures varies with age. Children younger than 12 months at the time of their first seizure have a 50 per cent risk of having recurrent seizures; this falls to 30 per cent when they are older than 12 months.

More than 90 per cent of second seizures will occur less than 24 months after the initial seizure.9

Simple febrile seizures have not been shown to cause a decline in IQ, academic performance, neurocognitive attention or behaviour problems. Prolonged seizures can rarely cause damage to the developing brain due to hypoxia. When a child is having a prolonged seizure, anti- convulsant medication should be used to stop the seizure.

Section 5: Case study
A five-year-old boy presented to A&E after having a generalised tonic-clonic seizure lasting eight minutes. The seizure was self-resolving and he was drowsy afterwards. He had previously experienced a febrile seizure at 15 months of age.

His temperature was 39.6Co on arrival in A&E, and he was starting to come round from the seizure. He had been noted to have a cough and runny nose for two days and, apart from the coryzal illness, examination was unremarkable.

In A&E he had a further generalised tonic-clonic seizure lasting two minutes and the decision was made to admit him for observation. On the ward he had a further three seizures within 45 minutes, ranging from three to eight minutes, these seizures were focal in nature affecting his right arm and leg. His temperature on arrival on the ward was 39.1Co despite antipyretics.

As he did not regain consciousness between these seizures he was judged to be in febrile status epilepticus. A cannula was inserted, bloods were sent for analysis and he was given IV lorazepam to stop the seizures in addition to broad spectrum IV antibiotics in the case of a more serious infection. The lorazepam stopped the seizures and he was closely monitored.

Later that evening he had fully recovered and was able to sit up to eat his dinner. After he had recovered from the seizures there was no evidence that he had meningitis, so a lumbar puncture was not performed. The blood tests were unremarkable except for a CRP of 18mg/L. His antibiotics were discontinued after 48 hours when his blood cultures were found to be negative. Although his temperature continued to spike while on the ward he had no more seizures.

He was allowed home after 72 hours when his coryzal symptoms and temperature were settling.

Risk factors
There was a very strong family history, with his mother, maternal aunt, maternal grandfather and both older siblings all having febrile seizures when younger. His mother had gone on to develop epilepsy in her adolesence. Apart from his family history he had no other risk factors.

Further management
In view of the number of seizures he had, an outpatient EEG was arranged to look for any epileptiform activity. This was normal. He was re-admitted to the ward five weeks later having had two further febrile seizures secondary to a viral illness. He is currently awaiting an outpatient appointment where we will discuss the use of intermittent diazepam with further febrile illnesses, to try to prevent future seizures.

Section 6: Evidence base
Clinical trials

Although many studies have been published looking into all aspects of febrile seizures, there are still many unanswered questions surrounding their pathogenesis and inheritance.

  • Strengell T, Uhari M, Tarkka R, et al. Antipyretic agents for preventing recurrences of febrile seizures. Arch Pediatr Adolesc Med 2009; 163(9): 799-804.

This study observed 231 children for two years and found that antipyretics are ineffective in preventing febrile seizures.

  • Rosman NP, Colton T, Labazzo J, et al. A controlled trial of diazepam administered during febrile illness to prevent recurrence of febrile seizures. N Engl J Med 1993; 329: 79-84.

This study followed 406 children for 1.9 years. It found that treatment with diazepam led to a reduction of 44 per cent in the risk of febrile seizures per child per year.

Guidelines

  • Waruiru C and Appleton R. Febrile seizures: an update. Arch Dis Child 2004; 89(8):751-6.

Hospitals have used this review to produce local guidelines for the management of patients with febrile seizures.

  • NICE. Feverish illness in children: Assessment and initial management in children younger than five years. CG47, London, NICE, 2007.

Although there is no specific NICE guideline for febrile seizures, the fever guideline specifically looks at the indications for further investigation of fever and indications for admission to hospital.

Key text
Panayiotopoulos CP. A Clinical Guide to Epileptic Syndromes and their Treatment. (Second Edition). London, Springer-Verlag, 2007.

This is a good textbook for information regarding any kind of childhood seizure.

Curriculum
This topic is covered in the GP curriculum in statement 15.7 Neurological Problems

Online

This NHS website has information for parents and caregivers of children with febrile seizures.

Click here to reflect on this article and add notes to your CPD organiser on MIMS Learning

CPD IMPACT: EARN MORE CREDITS

These further action points may allow you to earn more credits by increasing the time spent and the impact achieved.

  • Organise a meeting with parents to discuss febrile convulsions and the management of the sick child.
  • Design a surgery poster on febrile convulsions.
  • Hold a practice meeting discussing this article and management of a child with a fever.

References
1. Waruiru C and Appleton R. Arch Dis Child 2004; 89(8):751-6.

2. Nelson KB, Ellenberg JH. Pediatrics 1978; 61(5): 720-7.

3. Berg AT, Shinnar S, Levy SR et al. Neurology 1999; 53(8): 1742-8.

4. Virta M, Hurme M, Helminen M et al. Epilepsia 2002; 43: 920-3.

5. Armon K, Stephenson T, MacFaul R et al. Emerg Med J 2003;20(1):13-20

6. Gordon KE, Dooley JM, Camfield PR et al. Pediatrics 2001;108(5):1080-8.

7. Vestergaard M, Basso O, Henriksen TB et al. Arch Dis Child 2002; 86: 125-6.

8. Offringa M, Moyer VA. BMJ 2001; 323: 1111

9. Steering Committee on Quality Improvement and Management, Subcommittee on Febrile Seizures American Academy of Pediatrics.Pediatrics 2008; 121(6):1281-6

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