Febrile Convulsion (Seizures)
Seizure is defined as a paroxysmal involuntary disturbance of brain function that may be manifested as impairment or loss of consciousness, behavioral abnormalities, abnormal motor, sensory or autonomic function due to abnormal excessive, hyper synchronous discharges of CNS neurons.
What is febrile convulsion?
Febrile seizures are defined as epileptic seizures precipitated by fever, not due to an intracranial infection or other definable CNS cause in a genetically predisposed child of age between 6 months to 5 years.
Febrile seizures occur in 3% of all children between 6 months to 5 years of age. Majority occurs in the first 3 years of age. 3% of epileptic patients suffer from febrile seizure and 3% of febrile seizures turns into true epilepsy. (Rule of 3)
This is due to imbalance between the convulsant and anticonvulsant system in the brain triggered by fever in whom the convulsant threshold is not static to changes in temperature.
A strong family history of febrile seizure in siblings and parents suggest a genetic predisposition. Autosomal dominant inheritance is the most common mode of inheritance.
- Simple febrile seizure (70%-75%)
- Complex febrile seizure (25-30%)
Clinical feature of Simple Febrile Seizures: When we say “Febrile Seizures” it means simple febrile seizures. Below the diagnostic criteria for febrile seizure is given.
Criteria for Diagnosis of Febrile Seizure:
- Age of onset: Occurs mainly between 6 months to 5 years. Mostly around 18-20 months of age. Peak age of onset is 14-18 months.
- Physical Status: It occurs in otherwise normal children without any preexisting neurological and developmental deficit.
- Family history: fifty percent have family history of febrile seizures. Mode of inheritance is autosomal dominant, demonstrated in some families.
- Sex: The incidence is slightly higher in boys than in girls.
- Infection: 90% of cases are due to viral infection. Common infections are pharyngitis, otitis media, pneumonia, UTI, roseola.
- Vaccination: Especially DPT- may cause seizures.
- Pyrexia: 80% of simple febrile seizures occurs during first 24 hours. Mostly within 12 hours of onset of fever.
- Seizures: Onset within 24 hours of illness mostly within 12 hours.
Type of seizure- Generalized
Duration- Usually 10 minutes but not more than 15 minutes.
Number of attacks: The seizure is not repeated during the same illness. Usually one seizure at each episode and rarely two.
- Recurrence: 50% under 1 year and 30% in other situation. Frequency decreases after 5 years of age.
- Postictal phase: There is usually no residual weakness of limbs or disability except a brief period of drowsiness.
- Physical Examination: On examination no positive findings of meningitis or neurological abnormalities.
- EEG: EEG done within a week after a febrile convulsion may be abnormal, but after a week it usually shows no abnormality. EEG should not be advised routinely, as EEG change does not alter the course of febrile seizure or subsequent development of epilepsy.
Differential Diagnoses of Febrile Convulsion:
- Typhoid fever
- Blood: CBC (Blood sugar, serum electrolytes, blood culture if indicated)
- CSF- If indicated
- EEG, CT, MRI if not otherwise indicated
Lumbar puncture (LP) is not indicated in all cases of febrile convulsion. It depends on the experience and judgment of the doctor concerned. However if a child is below one year of age and coming with first episode or if the age is more than five years, LP should always be considered. In addition, if there is even slightest doubt of CNS infection as evidenced by undue prolongation of postictal state, it is always better to do an LP.
- Explanation and reassurance of parents.
- Removal of excess clothing
- Reduction of body temperature by tepid sponging. It is better to use normal tap0water and use a fan, rather than using ice-cold water.
- Paracetamol 10-15 mg/kg/dose can be given orally or rectally 4-6 hourly, when the temperature is more than 100 F
- In rare cases, when the temperature does not subside with paracetamol, Ibuprofen 5 mg/kg/dose three times daily can be given orally.
- The source of infection should be looked for and treated.
- Control of convulsion: Diazepam 0.3 mg/kg/dose can be given very slowly IV or 0.5 mg/kg PR. Required amount of diazepam is taken in 3 cc disposable syringe. The nozzle is attached to a 6 FG nasogastric tube (or to a tube of a butterfly needle), which is introduced into the rectum. Diazepam is now pushed into the rectum, and then 2 cc of normal saline is pushed through the tube. The tube is then withdrawn and the buttocks are approximated by hands or leucoplast for sometime. Nowadays, diazepam is available is suppositories, which can be used easily.
- The risk of recurrence can be reduced by diazepam 1 mg/kg/day (maximum 10 mg) PO 8 hourly for 2-3 days to be started at the onset of each febrile illness. Alternatively, oral Clobazam 1 mg/kg/day (max 20 mg) can be used considering same efficacy, single daily dose, and less ataxia and drowsiness compared to diazepam.
- Short-term anticonvulsant prophylaxis in not indicated.
- Prolonged anticonvulsant prophylaxis for preventing recurrent febrile convulsion is no longer recommended. Phenytoin and carbamazepine have no effect on febrile seizures. Phenobarbitone is ineffective, may decrease cognitive function. Sodium valproate is effective in the management of febrile seizures, but the potential risks of the drug do not justify its use in a disorder with an excellent prognosis irrespective of treatment.
Good. No adverse effect is seen on academic, or behavioral activity even if seizures are recurrent. Seizure type, treatment modalities, EEG changes do no alter eventual outcome as epilepsy.
Atypical Febrile convulsions:
Convulsion associate with fever persists for more than 15 minutes, occurs Tours more than once in 24 hours, focal or unilateral in nature and /or is followed by Todd’s paralysis, but no significant other reason or CNS infection cannot be found for the fit, it may be called atypical febrile convulsion. In these children, the EEG may remain abnormal for 2 weeks or more following the attack. In these cases, continuous prophylaxis therapy may be given.
Criteria for prophylactic Anticonvulsant therapy:
- Patient under 18 months of age with previous abnormal development or abnormal neurological sigs.
- Atypical febrile seizures.
- Recurrent febrile seizures.
- High level of parental anxiety.
Continuous daily prophylaxis can be given with sodium valproate 30-60 mg/kg/day in two divided doses, to be continued for at least 2 year fit-free or until the child is 6 years old, whichever comes earlier.