Febrile Seizures

Question 1

Defintion of febrile seizures

Answer 1

Seizure occurring in febrile children between the ages of 6 and 60 months who do not have an intracranial infection, metabolic disturbance or a hx of afebrile seizures.

Question 2

Epidemiology of febrile seizures

Answer 2

Common in childhood. Incidence is between 2%-5% in the US and Western Europe, between 6% and 9% in Japan and 14% in India and Guam. 14% in Mariana Islands. Higher rates in the Pacific, may be explained by genetic factors or epidemic fevers. In Asia, most common cause is influenza A, especially prevalent in epidemics. 1.6 boys : 1 girl is the ratio.

Question 3

Etiology of Febrile Seizures

Answer 3

Viral infections triggering fever are most common with bacteraemia as an infrequent cause. Human herpesvirus (HHV-6) infection was commonly associated with febrile status epilepticus. Influenza A is the most common cause in Asian countries. Adenovirus, respiratory syncytial virus, herpes simplex virus, rotavirus are also causes.

Question 4

Pathophysiology of febrile seizures

Answer 4

Febrile seizures are dependent upon a threshold temperature. Age plays an important role in susceptibility of febrile seizures, the risk of recurrence of seizure declines with growing older.

Question 5

Classification of febrile seizures

Answer 5

A simple febrile seizure is characterized by generalised tonic-clonic activity without focal features for less than 10 minutes, without a recurrence in the subsequent 24 hours and resolving spontaneously.

Complex febrile seizures: defined by one or more of the following features: a focal onset or focal features during the seizure, prolonged duration (greater than 10 to 15 minutes) and recurrent within 24 hours or within the same febrile illness.

Question 6

Risk factors for febrile seizures

Answer 6

Strong:
Temperature elevation - risk doubles for each degree above 37.8 degrees celsius
Young age
Family history of febrile seizures
Viral or bacterial infection outside CNS e.g. otitis media, certain viruses, viral infections, proinflammatory cytokines and immune response → temperature elevation is the main trigger

Weak:
Male sex
Vaccinations 
Antenatal exposure to nicotine 
Iron deficiency
Complications of pregnancy, labour and delivery

Question 7

Hx and Examination of febrile seizure

Answer 7

Common:
Presence of risk factors (listed above)
Febrile illness (immediately before or at seizure onset)
Seizure
Other diagnostic factors:
Normal postictal exam: neurological examination normal postictally

Question 8

Investigations of febrile seizures

Answer 8

Diagnosis is clinical. Tests may be required to identify the source of fever. Result: seizures associated with fever.

Consider:

1. Lumbar puncture → indicated to rule our meningitis or encephalitis. Result: normal cells, protein and glucose
2. Viral Studies → may be useful in patients with complex febrile seizures and sx of encephalitis or encephalopathy. Result: may be positive
3. Blood culture → bacteremia is rare but meningitis should always be considered. Result: bacteremia may be present.
4. EEG. Result: possible focal EEG slowing or attenuation following febrile status epilepticus
5. Brain MRI → may show hippocampal oedema or sclerosis with complex, prolonged and focal febrile seizures. Result: may show acute hippocampal oedema or chronic hippocampal sclerosis
6. Serum sodium → hyponatremia may increase the risk for multiple seizures during the same febrile illness. Result: may be low (<130mmol/L or 130mEq/L)
7. FBC - not routinely recommended but may be required to determine the cause of fever. Result: variable
8. Serum glucose: usually normal. Result: usually normal
9. Iron studies → consider testing if clinically indicated. Result: may reveal deficiency

Question 9

Management of febrile seizures

Answer 9

1st line: consultation with paediatric neurologist or paediatric intensivist

Acute:
First simple febrile seizure and first complex seizure
1st line: antipyretic
Primary options: ibuprofen: children 6 months - 12 years of age: 5-10 mg/kg orally Q6-8H when required, maximum 40 mg/kg/day
OR paracetamol: 10-15mg/kg orally/rectally Q6-8H when required, max 75mg/kg/day

Adjunct: Anticonvulsant
Primary options:
Diazepam: children <2y/o : consult specialist for guidance of dose
Children 2-5 y/o : 0.5mg/kg rectally as single dose, may repeat in 4-12H if required
Children 6-11 y/o: 0.3 mg/kg rectally as single dose: may repeat in 4-12H if required

Midazolam: children 1-2 months of age: 300 micrograms/kg (maximum 2.5mg/dose) buccally as single dose, repeat after 10 minutes if required
Children 3-11 months: 2.5 mg buccally as single dose, repeat after 10minutes f required
1-4 y/o: 5mg buccally as single dose, repeat after 10 minutes if required
5-9 y/o: 7.5 mg buccally as single dose, repeat after 10 minutes if required
10-17 y/o: 10mg buccally as a single dose, repeat after 10 minutes if required

Secondary options:
Fosphenytoin: infants and children: 15-20mg/kg (phenytoin equivalent) IV as single dose: consult specialist about dose

Tertiary options:
Diazepam: infants and children: 0.1 to 0.3mg/kg IC as a single dose, may repeat after 5-10 minutes if required, maximum 10mg/dose
Lorazepam: infants and children : 0.05 to 0.1mg/kg IV as a single dose may repeat every 10-15 minutes if required, maximum 4mg/dose

Ongoing febrile illness with prior hx of simple seizure or 1 complex seizure:

1st line: antipyretic:
Ibuprofen: children 6 months-12 years of age: 5-10mg/kg orally Q6-8H when required, maximum 40 mg/kg/day
OR
Paracetamol : 10-15mg/kg orally/rectally Q4-6H when required, maximum 75mg/kg/day

Adjunct:
Prophylactic diazepam:
Children >6 months: 0.3mg/kg orally Q8H

Hx of 2 or more complex febrile seizures with ineffective diazepam

Long term anticonvulsant treatment may be considered in consultation with a neurologist