Introduction

A febrile seizure is defined by international league against epilepsy (ILAE) as:

“A seizure associated with a febrile illness not caused by an infection of the central nervous system, without previous neonatal seizures or a previous unprovoked seizure and not meeting the criteria for other acute symptomatic seizure, which occurs in children aged 6 months to 6 years” (1).

 

Epidemiology

Febrile convulsions/seizures are the most common neurological condition in paediatrics, with a peak incidence between the ages of 12-18 months (2). It affects 2-5% of children in Western Europe and the United States (3).

Pathophysiology

The specific cause a febrile seizure is unknown (1).  It is generally believed to be multifactorial with a combination of predisposing genetic and environmental factors.

One theory is that it is a reaction of the developing brain to a fever (2). As the child’s brain develops there is an increase in neuronal excitability, and it is thought that this increased excitability, in combination with environmental factors, makes the child more prone to a seizure (2).

In one third of cases, there is a positive family history in either or both parents (1,3). Twin studies have shown a predisposing genetic component along with numerous possible loci which are thought to be associated with febrile convulsions (2). However, a single susceptibility gene for febrile seizures has not yet been identified (3).

Viral infections are associated and triggering factors in 80% of febrile convulsion cases. The most common causes include upper respiratory tract infections (URTI), lower respiratory tract infections (LRTI), otitis media, and urinary tract infections (UTI) (2,4). Gastroenteritis and fever post-vaccination are also associated, but are not as common (5).

Risk factors

• Family history
• Socio-economic class
• Seasonal (higher prevalence of viral disease in the winter months)
• Zinc and iron deficiency

(1,2,5)

Clinical features

History

• Fever (>38°C) – ask about peak temperature.
  • The use of antipyretics does not reduce the recurrence risk (3,6,7).
• Age – approximately 6 months to 6 years. There is no fixed lower and upper age limits, although to diagnose a febrile seizure under the age of 3 months would be exceptional and should only be done after thorough exclusion of other causes of seizure.
• Tonic-clonic seizure
  • The child may become tense and then begin to shake or twitch.
  • Seizures are generalized and may be associated with up rolling of the eye balls, tongue biting and/or incontinence.
  • Usually occurs in the first day of fever (2).

• Constitutional symptoms suggestive of infective or other etiology of accompanied fever such as of respiratory (cough, sore throat, pulling of ears, ear ache), gastrointestinal (diarrhea, abdominal pain, vomiting), genitourinary (dysuria, increased frequency of urination) and recent immunization (8).

Seizures can be classified into simple or complex (1)

30-35% of febrile seizures have one or more complex features (3).

Febrile status epilepticus – a subgroup of complex febrile seizure where the seizure duration exceeds 30 minutes, or there are multiple seizures lasting a total of 30 minutes without recovery between each one (1).

Important questions to remember

• Has the child been vaccinated?
• Are they currently at school?
• Previous treatment with antimicrobials?
• Any history of trauma or toxin ingestion?
• Any family history?
• Developmental history?

Examination

The focus of the examination is to ensure that the child is safe after their seizure and to find the source of the infection.

Examine from head to toe with special emphasis on:

• External ear examination with auroscope – to look for any signs of otitis externa or otitis media (red bulging tympanic membrane etc.)
• Throat examination – for signs of URTI (inflamed tonsils etc.)
• Full respiratory examination – looking for signs of LRTI
• Check fontanelles (raised anterior fontanelles with no pulsation felt in infants can be a sign of meningitis or raised ICP)
• Brudzinski’s or Kernig’s sign, (signs of meningitis, though less reliable in infants)
• Nuchal rigidity (neck stiffness)
• Mental status of the child (irritable, playful)
• Full neurological examination
• Cardiovascular examination
• Abdominal examination
• Urine dipstick and microscopy
• Any superficial infective skin lesions

Differential Diagnosis

• CNS infection – such as meningitis
  • Look out for red flag symptoms – fever, headache, neck stiffness, photophobia, bulging fontanelles, decreased consciousness, focal neurology.
• Delirium
  • This is more commonly seen in geriatrics however can also be seen in children and can be associated with fever. This is known as febrile delirium.
  • Look out for cognitive changes, changes in the behavior of the child, emotional disturbances and a lack of awareness of surroundings.
• Syncope
  • A loss of consciousness due to decreased perfusion to the brain. Described as having a rapid onset, short duration and a quick complete recovery.
• Epilepsy
  • Be suspicious if the history of fever is unconvincing, the seizure is complex, focal in nature, and if the child has past history of any neurological problems including developmental delay, structural brain pathology or afebrile seizure.

(1,2,8,9)

Investigations

General observations should be undertaken (e.g. temperature, heart rate, respiratory rate, oxygen saturation, mental status etc.) to confirm fever and monitor for signs of sepsis etc.

Other investigations are usually unnecessary with a simple febrile convulsion where there is a clear source of infection.

The overall risk of bacterial meningitis is 0.2% in children with an apparent first simple febrile seizure, and 0.6% in children following a complex febrile seizure (10). If the source of infection is unknown, the child is >1 year old, or they have symptoms of intracranial infection, then you can consider:

• Bedside testing – urinalysis.
• Bloods – FBC, CRP, U&E, corrected calcium, glucose, magnesium, and blood cultures.
• Stool cultures.
• Lumbar puncture – Not recommended in straightforward cases of simple febrile seizure. Green et al (11) reviewed over 500 cases of meningitis in children aged 2 months to 15 years and found that meningitis was associated with seizures in 23% of cases, but all of these patients presented with signs in addition to the fever and seizure. Bear in mind that signs of meningitis may be minimal in an infant less than 18 months of age.
• Imaging – chest X- Ray is the recommended initial imaging.
• CT/MRI/EEG are not generally done with simple febrile seizures but should be considered in complex seizures, especially if they recur without fever or there are neurological signs or deficits

(2,5,7).

Management

Most children who have had a febrile seizure present to the emergency department after the seizure has occurred (1). Short febrile seizures of less than 5 minutes do not need any specific treatment.

Acute management

• Always follow ABCDE (Airway, Breathing, Circulation, Disability and Exposure) approach.
• General measures such as monitoring the child and preventing injuries by cushioning the head and removing nearby potential hazardous objects are very important (1).
• Keep the child well hydrated (7).
• Paracetamol or ibuprofen – helpful in reducing the temperature and distress but does not decrease recurrence (7).
• In-depth explanation – spend adequate time explaining the diagnosis as it can be a traumatic experience for both the parents and child (8, 12).

Prolonged febrile convulsions or recurrent seizure without complete resolution in between must be treated (8). A seizure longer than 5 minutes should be treated as it is unlikely to spontaneously resolve (1,13).

• If the seizure lasts for >5 minutes give emergency benzodiazepine rescue treatment (1), then continue to follow the APLS guideline for status epilepticus (14).

Further treatment

Criteria for admission to hospital can vary depending on the hospital trust, however in general:

• All complex febrile seizures should be admitted to hospital, as well as children who have received medication to stop the seizure (12).
• A child with a first presentation of simple febrile seizure in good practice should be admitted, however often they may be sent home the same day (after a period of observation (7)) provided the child has been reviewed by a senior clinician except:
  • Infants less than 18 months old.
  • Where there is no obvious source of infection.
  • Where there is significant parental anxiety (or they request it).

(12,14)

Complications

Up to a third of the children with febrile seizure may have a recurrence, with majority recurring within the first year after the first febrile seizure (17).

Risk factors for recurrent febrile seizures

• Age at onset under 18 months.
• Shorter duration of fever before seizure (<1 hour).
• Relatively lower grade of fever associated with seizure (<40C).
• Multiple seizures during the same febrile illness.
• Day nursery attendance.
• Family history of febrile seizure in a first degree relative.

Children meeting all of these risk factors having up to 80% risk of recurrence.

Risk of epilepsy

Most febrile seizures have no long term sequelae, however there is an association with epilepsy. Studies have shown an overall risk of 2-7% of a child developing epilepsy following febrile seizures. There also appears to be a difference between simple and complex febrile seizures. The risk ranges from 2.4% among children with simple febrile seizures, to 6-8% among children with febrile seizures with a single complex feature (13,18).

Risk factors predicting development of future epilepsy are different to the risk factors predicting recurrence of febrile seizure. The three main risk factors predicting development of future epilepsy are:

• Family history of epilepsy.
• Complex focal seizure.
• Neurodevelopmental impairment.

References