Neurology
A 2 year old is brought to the Emergency Department by his parents. They describe him having a seizure that lasted "a few minutes". They describe tonic-clonic like movements. He has never had any episode like this before. Twenty minutes later he had returned to his normal self. He has had a dry cough and coryza for the last 48 hours. His temperature is 38.2°C and his other observations are within normal limits for his age. His examination is unremarkable. What is the next step in this patient's management?
Answer:
No investigations are indicated in a simple febrile seizure, where the focus of infection can be identified clinically and the child returns to baseline mental state. Investigations for the source of fever, including lumbar puncture, should be guided by the nature of the presentation and age of the child.Febrile Seizure
Neurology
Last Updated: 18th July 2021
A febrile seizure is a seizure accompanied by fever (temperature higher than 38°C by any method), without central nervous system infection, which occurs in infants and children aged 6 months to 6 years.
Classification
- Simple febrile seizures are isolated, generalised, tonic-clonic seizures lasting less than 15 minutes, that do not recur within 24 hours or within the same febrile illness, with complete recovery within 1 hour.
- Complex febrile seizures have one or more of the following features: a partial (focal) onset or focal features during the seizure; duration of more than 15 minutes; recurrence within 24 hours, or within the same febrile illness; or incomplete recovery within 1 hour.
- Febrile status epilepticus describes a subgroup of complex febrile seizure where a febrile seizure lasts for 30 minutes or longer, or there are a series of seizures without full recovery in between that last for 30 minutes or longer.
Causes
The exact cause of febrile seizures is unknown, but is thought to be an age-dependent response of the immature brain to fever, in combination with underlying genetic and environmental factors.
Any febrile illness may cause febrile seizures, including:
- Viral infection — this is the cause of fever in 80% of cases, with human herpesvirus 6 (HHV-6) which causes roseola infantum (sixth disease) and influenza being common triggers
- Other infections — viral upper respiratory infections, otitis media, lower respiratory tract infection, urinary tract infection, and gastroenteritis are also common causes
- Post-immunisation (rare) — vaccination with diphtheria-tetanus-pertussis and measles-mumps-rubella, for example, may be associated with an increased risk of febrile seizure
About 50% of children who present with a febrile seizure have no identified risk factors, but possible risk factors for a first febrile seizure include:
- Family history of febrile seizure in first-degree relatives
- The peak temperature (rather than the rapidity of the temperature rise)
- Zinc and iron deficiency
Clinical features
Suspect a diagnosis of febrile seizure if a child has a fever or febrile illness and a reported or witnessed seizure. Typical features of a simple febrile seizure include:
- The child is aged 6 months to 6 years.
- The seizure usually lasts 2–3 minutes, and rarely lasts more than 10 minutes.
- The seizure is a generalised tonic-clonic type (muscle stiffening followed by rhythmical jerking or shaking of the limbs, which may be asymmetrical); twitching of the face; rolling back of the eyes; staring and loss of consciousness.
- There may be foaming at the mouth, difficulty breathing, pallor, or cyanosis.
- A brief postictal period of drowsiness, irritability, or confusion, with complete recovery within 1 hour.
- The child may have had a previous febrile seizure.
Differential diagnosis
Other conditions that may present similarly to a febrile seizure include:
- With fever
- Central nervous system infection such as bacterial meningitis/meningococcal disease or encephalitis - red flags include irritability, neck stiffness, petechial rash, photophobia, bulging fontanelle, decreased level of consciousness, prolonged post-ictal period, and focal neurological deficit (lasting more than one hour)
- Rigors or delirium (acute confusional state)
- Shivering (may occur with or without fever)
- Febrile myoclonus
- Without fever
- Syncope - characterised by a rapid onset, short duration, and spontaneous complete recovery
- Breath-holding spells or reflex anoxic seizures - may present with pallor or cyanosis and low tone, with possible loss of consciousness and transient tonic clonic movements if the apnoea is prolonged
- Head injury
- Hypoglycaemia or other metabolic disorders, such as a mitochondrial cytopathy
- Drug use or withdrawal
- Epilepsy — suspect if there is no compelling history of fever, the seizure was complex, there were postictal signs, or there is neurodevelopmental delay
- Other neurological conditions such as cerebral palsy or neurocutaneous syndromes where seizures may form part of the condition
Parental advice
Provide advice and education to parents/carers about the nature of febrile seizures:
- Febrile seizures are not the same as epilepsy, and the risk of a child developing subsequent epilepsy is low.
- Short-lasting seizures are not harmful to the child.
- About 1 in 3 children will have another febrile seizure.
- The risk of febrile seizure reduces with age as the brain matures, and they are rare beyond 6 years of age.
Provide written advice on the management of any future febrile illness:
- Advise that the intermittent use of antipyretics such as paracetamol and/or ibuprofen at the onset of fever is not recommended, as this does not reduce or prevent febrile seizure recurrence.
- Advise on the use of paracetamol and/or ibuprofen to reduce fever if the child is uncomfortable or distressed, and on measures to prevent dehydration.
- Advise on when to seek immediate medical help if a serious or life-threatening cause of fever is suspected.
- Advise parents/carers to ensure the child completes all childhood immunisations, even if the febrile seizure followed an immunisation.
Advise parents/carers that if a child is having a suspected acute febrile seizure:
- Give immediate first aid to the child:
- Monitor the duration of the seizure by noting the time it starts.
- Protect the child from injury during the seizure by:
- Cushioning their head with your hands or soft material.
- Removing harmful objects from nearby, or if this is not possible, moving the person away from immediate danger.
- Do not restrain the child or put anything in their mouth.
- Check the airway and place the child in the recovery position when the seizure has stopped.
- Observe the child until they have recovered.
- Examine for, and manage, any injuries.
- If tonic-clonic movements last for more than 5 minutes:
- Call an emergency ambulance, or
- Give emergency benzodiazepine rescue medication if this has been advised by a specialist for a child with recurrent febrile seizures.
Prognosis
Following a first febrile seizure, approximately 30% of children will have recurrent seizure.
Risk factors for recurrent febrile seizures include:
- Early onset under 18 months of age
- Family history of febrile seizures or epilepsy in a first-degree relative
- Low-grade fever associated with seizure onset (less than 39°C)
- Short duration of fever before the seizure (less than 1 hour)
- History of complex febrile seizure
- Multiple seizures in 24 hours or during the same febrile episode
- Prolonged febrile seizure (lasting more than 15 minutes)
- Attendance at a day care nursery — presumed increased viral exposure and frequent febrile illness
Febrile seizures are generally benign with a normal cognitive outcome. Possible complications following febrile seizure include:
- Parental/carer anxiety
- Febrile status epilepticus
- Epilepsy
- Cognitive impairment
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- Biochemistry
- Blood Gases
- Haematology
| Biochemistry | Normal Value |
|---|---|
| Sodium | 135 – 145 mmol/l |
| Potassium | 3.0 – 4.5 mmol/l |
| Urea | 2.5 – 7.5 mmol/l |
| Glucose | 3.5 – 5.0 mmol/l |
| Creatinine | 35 – 135 μmol/l |
| Alanine Aminotransferase (ALT) | 5 – 35 U/l |
| Gamma-glutamyl Transferase (GGT) | < 65 U/l |
| Alkaline Phosphatase (ALP) | 30 – 135 U/l |
| Aspartate Aminotransferase (AST) | < 40 U/l |
| Total Protein | 60 – 80 g/l |
| Albumin | 35 – 50 g/l |
| Globulin | 2.4 – 3.5 g/dl |
| Amylase | < 70 U/l |
| Total Bilirubin | 3 – 17 μmol/l |
| Calcium | 2.1 – 2.5 mmol/l |
| Chloride | 95 – 105 mmol/l |
| Phosphate | 0.8 – 1.4 mmol/l |
| Haematology | Normal Value |
|---|---|
| Haemoglobin | 11.5 – 16.6 g/dl |
| White Blood Cells | 4.0 – 11.0 x 109/l |
| Platelets | 150 – 450 x 109/l |
| MCV | 80 – 96 fl |
| MCHC | 32 – 36 g/dl |
| Neutrophils | 2.0 – 7.5 x 109/l |
| Lymphocytes | 1.5 – 4.0 x 109/l |
| Monocytes | 0.3 – 1.0 x 109/l |
| Eosinophils | 0.1 – 0.5 x 109/l |
| Basophils | < 0.2 x 109/l |
| Reticulocytes | < 2% |
| Haematocrit | 0.35 – 0.49 |
| Red Cell Distribution Width | 11 – 15% |
| Blood Gases | Normal Value |
|---|---|
| pH | 7.35 – 7.45 |
| pO2 | 11 – 14 kPa |
| pCO2 | 4.5 – 6.0 kPa |
| Base Excess | -2 – +2 mmol/l |
| Bicarbonate | 24 – 30 mmol/l |
| Lactate | < 2 mmol/l |
