Febrile Convulsions

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

There is no definition of "febrile" in this context, but consensus guidelines agreed:²

• Axillary temperature > 37.8°C.
• OR: clinical history and examination indicative of febrile seizure.

Types of febrile seizure³

The recognised categories are:

1. Simple febrile seizures are generalised, tonic–clonic seizures lasting less than 15 minutes, that do not recur within 24 hours or within the same febrile illness.
2. Complex febrile seizures 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.
3. Febrile status epilepticus is a febrile seizure lasting for longer than 30 minutes.

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 outcome 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:

• Viral infections
• Otitis media
• Tonsillitis

• Meningitis and septicaemia
• Urinary tract infection
• Lower respiratory tract infection
• Cerebral malaria (if relevant)⁵

Other causes of fever with seizure are:

• Gastroenteritis
• Post-immunisation

• If the child is still convulsing or drowsy: check blood glucose, check and maintain Airway, Breathing, Circulation (see management).
• History, including:
  • Eye witness account of the seizure: conscious level prior to seizure, duration, focal or generalised, time taken to recover and state of child afterwards.
  • Symptoms of meningitis or septicaemia, such as: rapid onset of illness, abnormal behaviour or cry, stiff or floppy, vomiting, (and meningism in older children). Early symptoms are: leg pains, cold hands and feet, pallor or mottled skin.⁶
  • 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 to the normal range for child's age).^7,8
  • The NICE traffic light system can help assess likelihood of serious illness in a child with fever.⁷

Who needs urgent referral or admission?

From the community or A&E, refer to paediatrician if³

• First febrile seizure.
• Serious illness not excluded.
• Previous history of febrile seizure, with:
  • Child < 18 months of age (meningitis harder to detect in this age group).
  • Diagnostic uncertainty about cause of present seizure.
  • A complex seizure (as defined above - these are more likely to recur or be due to intracranial infection compared to 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 found (for a period of observation and to investigate for UTI).
• Others may be managed at home if:
  • 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.

At hospital assessment²

• Admit and treat as meningitis if any "serious features":
  • Drowsy before seizure or 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), if:
  • Under age 18 months
  • Complex seizure
  • Child has had antibiotics
  • Consider admission if no focus of infection 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: full blood count, ESR, glucose, U&E, coagulation, PCR, culture
• Urine microscopy/culture if: age < 18 months, complex seizure or no focus of infection found
• Lumbar puncture (LP) should be considered for:
  • Child < 12 months - LP advised unless paediatric registrar decides against LP and will review within 2 hours
  • Child 12-18 months - have a low threshold for LP
  • Any "serious features" (see hospital assessment above)
• Contraindications to LP are:
  • Reduced consciousness (GCS < 13 or falling conscious 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 (e.g. 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 seizure lasted >10 minutes; usually have temperature < 38°C)
• Other cause of seizures, e.g. epilepsy, head injury, encephalitis, hypoglycaemia, hypocalcaemia, poisoning, other metabolic disorders, neurological disorders
• Afebrile seizures with gastro-enteritis¹ (see above)

• Review child and address parents' questions.
• Consider out-patient referral if:
  • An alternative cause for seizures is suspected, e.g. epilepsy or a neurodevelopmental condition.
  • Prophylaxis with anticonvulsants is being considered (see below).
  • Parental request or concerns.
• Prophylaxis of febrile seizures may be considered for situations such as prolonged seizures or 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 antiepileptic drugs in this scenario.

Generally the prognosis is good:

• By definition, febrile seizures do not recur beyond age 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, 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).

• Immunizations 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.
• Antiepileptic 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.