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Febrile Seizures

Febrile seizures are the most common form of childhood seizures, affecting between 2% and 4% of children. Febrile seizures are age specific seizures. The increased susceptibility to seizures is due to fever. The peak incidence of febrile seizures is at approximately 1 years of age. Febrile seizure is a seizure in association with a febrile illness in the absence of a CNS infection or acute electrolyte imbalance in children older than 1 month of age without prior afebrile seizures. Febrile seizures can be classified as either simple or complex. A simple febrile seizure is isolated, brief, and generalized. Conversely, a complex febrile seizure is focal, multiple (more than one seizure during the febrile illness), or prolonged, lasting either more than 10 or 15 minutes. Most febrile seizures are simple. The majority of febrile seizures do not occur at the onset of the fever.

Risk Factors for Recurrent Febrile Seizures:
Overall, approximately one-third of children with a first febrile seizure will experience a recurrence; 10% will have three or more febrile seizures. The most consistent risk factors reported are a family history of febrile seizures and onset of first febrile seizure at 18 months of age. Other risk factors for recurrence are low peak temperature and duration of fever. In general, the higher the peak temperature, the lower is the chance of recurrence. The other risk factor related to the acute illness is duration of recognized fever, with a shorter duration of recognized fever associated with a higher risk of recurrence. Children with multiple risk factors have the highest risk of recurrence.

Genetic influence for febrile seizures is evident in several studies. A positive family history of febrile seizures is a definite risk factor for both a first febrile seizure and recurrent febrile seizures. There may be a subset of children with an autosomal dominant mode of inheritance.

Risk Factors for Subsequent Epilepsy:
2% to 10% of children who have febrile seizures will subsequently develop epilepsy. Following a single simple febrile seizure, the risk of developing epilepsy is not substantially different from the risk in the general population. Family history of epilepsy and the occurrence of a complex febrile seizure are associated with an increased risk of subsequent epilepsy. The occurrence of multiple febrile seizures, very prolonged febrile seizures (i.e., febrile status epilepticus), and shorter duration of fever is associated with an increased risk of subsequent epilepsy. Children with neurodevelopmental abnormality also are at risk for subsequent epilepsy.

It is controversial whether febrile seizures are simply an age-specific marker of future seizure susceptibility or have a causal relationship with the subsequent epilepsy.

Morbidity and mortality:
There is no evidence of permanent motor deficits following febrile seizures or febrile status epilepticus. No reports of acute deterioration of cognitive abilities have been noted following febrile seizures. Even prolonged febrile seizures are not associated with adverse cognitive outcomes.

Meningitis, encephalitis, serious electrolyte imbalance, and other acute neurological illnesses must be excluded in order to make the diagnosis of a febrile seizure. A detailed history and physical and neurological examinations are essential.

Lumbar puncture if febrile seizures:
The most common evaluation issue is whether a lumbar puncture is necessary to exclude meningitis. Features noted in children with meningitis are: seizures on arrival to the emergency room; focal seizure; suspicious findings on physical or neurological examination. In the absence of risk factors there is a low yield for routine lumbar puncture. A lumbar puncture should be strongly considered in infants less than 12 months of age. In the absence of suspicious findings on history or examination, a lumbar puncture is not necessary in children above 18 months of age. A lumbar puncture is recommended in children with a first complex febrile seizure, as well as in any child with persistent lethargy.

EEG in febrile seizures:
Electroencephalograms (EEG) are of limited value in the evaluation of the child with febrile seizures. The clinical significance of EEG abnormalities in febrile seizures is unclear. There is no evidence so far that EEG abnormalities help predict either recurrence of febrile seizures or the development of subsequent epilepsy.

Febrile seizures and mesial temporal sclerosis (MTS):
Studies suggest that prolonged febrile seizures (> 30 min duration) can cause acute hippocampal injury in 2030% of cases and that these may lead to hippocampal volume loss and MTS.

Febrile seizures are benign and hence the aim is to abort febrile seizures to prevent status epilepticus. If the child has a seizure on arrival to hospital, initiating therapy with intravenous diazepam is effective in most cases. Rectal diazepam or diazepam gel is appropriate for use in a prehospital setting, such as an ambulance, and in cases where intravenous access is difficult. The majority of febrile seizures are brief, lasting less than 10 minutes, and no intervention is necessary.

Preventing a Febrile Seizure:
Intermittent medications at time of fever can prevent febrile seizures in high risk children. Aggressive treatment with antipyretic medication can reduce the risk of having a febrile seizure. Benzodiazepines like diazepam, given orally or rectally or clobazam given orally at the time of onset of a febrile illness reduce the probability of a febrile seizure.

Daily Medications:
Phenobarbital and valproate are effective in reducing the risk of recurrent febrile seizures. These medications have concerns about potential long-term adverse effects on cognition and behavior. Valproate can cause idiosyncratic hepatotoxicity. Chronic phenobarbital or valproate therapy is rarely indicated, as the risks seem to outweigh the benefits in most cases.

Preventing Epilepsy after febrile seizures:
Preventing febrile seizures with daily antiepileptic medications does not reduce the risk of getting subsequent epilepsy hence this is not recommended.

The best treatment for simple febrile seizures is reassurance of the parents regarding their benign though frightening nature. Treatment is only rarely indicated for a simple febrile seizure. Counseling and Education is important for parents.