Febrile seizures
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Martin L. Kutscher, MD; Departments of Pediatrics and Neurology, New York Medical
College, Valhalla, NY.
Introduction
Febrile seizure are very common, and occur in 3-4% of all children. They have an
average age of onset of 24 months, and are rare <6 months or >5-6 years of age. They
usually occur within 24 hours of onset of fever to >39 degrees. Febrile seizures can be
classified as simple, complex, or atypical.
"Simple febrile seizures" last <15 minutes, are generalized, and
occur only once per 24 hours.
"Complex febrile seizures" last >15 minutes, have a focal onset, or
occur more than once per 24 hours.
"Atypical febrile seizures" differ in some other way from the above,
such as a lower temperature than usual, unusual age of the child, etc. The more the
seizure diverges from the classical syndrome, the better it is to call the events
"seizures with fever." Such a label reminds us that we do not yet have a
diagnosis. Febrile seizures should rarely be diagnosed in children who have afebrile
seizures.
Although usually benign, febrile seizures are very frightening to the parents. It may
not seem like a major deal to us--now that the child is better and we have the backup of
all of our equipment and staff--but the parents were likely convinced that they just
witnessed the impending death of their child. Reassurance is key--both by careful medical
evaluation and by our words.
Diagnostic Studies
Lumbar Puncture
According to the AAP practice parameter, about 15% of children with meningitis present
with seizures; and, in 1/3 of these children (primarily <18 mo.) meningeal sx and
symptoms may be missing.(AAP Practice Parameter1) In contrast, another study
found a low incidence of clinically unsuspected meningitis in patients with seizures and
fever (Green2). It should be additionally noted that a recognized source of
fever does not exclude meningitis (nor does a previous febrile seizure). Risk factors for
meningitis are given in Table 1, along with the risk factors for failure to diagnose CNS
infection (Table 2). Indications for lumbar puncture in the setting of seizures with fever
are given in Table 3.
Table 1.
Risk factors for meningitis
in seizures with fever
suspicious physical or neurological findings
complex febrile seizure
physician visits within 48 hours before the seizure
seizures on arrival to the ER
prolonged post ictal state
initial seizures >3 years old.
Table 2.
Risk factors for failure to diagnose
meningitis in seizures with fever
children <18 months old
less-experienced doctor
poor follow up
Table 3.
Indication for lumbar puncture
Recognizing that practice differs, this author would suggest a lumbar puncture:
routinely if child is < 24 months. [The AAP practice parameter for first febrile
seizures is slightly less cautious. They recommend that a LP be "strongly
considered" for children who were previously on antibiotics or for children <12
mo, "considered" for children 12-18 mo., and recommended if intracranial
infection is suspected for children >18 mo.]
history or physical suggestive of intracranial infection
if patient was or will be placed on antibiotics
if patient will be sedated with anticonvulsants
Atypical or complex febrile seizures are at a higher risk of serious pathology, and
generally need CT scan, lumbar puncture, and admission.
Note: Some physicians suggest lumbar puncture for all first febrile seizures.
Bloods
CBC and routine chemistries not indicated for simple febrile seizures unless suggested
by patient’s history, physical, or need for evaluation of the fever itself (per AAP).
However, most physicians get them, anyway.
EEGs, CTs, and MRIs
EEGs, CTs, and MRIs are not recommended in a neurologically healthy child with a first
simple febrile seizure. They are usually obtained if the seizures are complex or atypical,
the child is neurologically abnormal, or if there are multiple febrile seizures. Even so,
studies fail to show the usefulness of EEGs of predicting epilepsy in these cases. CTs and
MRIs are discussed above.
Hospitalization
Children with typical simple febrile seizures are usually not hospitalized, assuming
they look well, do not need hospitalization for general pediatric reasons, have been
observed for several hours, and have reliable caretakers who are comfortable watching the
child at home. Atypical or complex features place the children at risk for underlying
pathology, and usually indicate the need for in-patient observation or treatment.
Risks and Treatment Options
In order to make logical decisions about long term treatment, the caregiver and parents
need some underlying information. Although febrile seizures may well recur, even prolonged
ones are unlikely to cause damage or epilepsy. The data underlying these issues are
discussed in Table 4.
Armed with this information, we can make logical choices with the family regarding
appropriate long term treatment options. Since the risk of developing epilepsy after
febrile seizures is low, it does not make sense to treat a child with long term
anticonvulsants just in case a few percent might develop epilepsy years into the future.
Thus, most treatment options are aimed at preventing recurrent febrile seizures--events
which we have seen are unlikely to cause damage. Options include rectal diazepam (table 5)
and phenobarbital prophylaxis (table 6). Valproate (Depakane (TM)) prophylaxis is also
effective for febrile seizure prophylaxis, but is rarely used in this setting because of
its risks in this age range. Phenytoin (Dilantin (TM)) is not felt to be effective in the
treatment of febrile seizures. Treatment should also include instruction on first aid for
seizures and agressive temperature control. AAP recommendations regarding pertussus
immunizations are found in the "Red Book."
Table 4.
Risks of Febrile Seizures
Take Home Message
for Families and Caregivers |
Supporting Data |
| Febrile seizures recur in 1/3 of children who have had a
febrile seizure. [Nelson] |
The risk ranges from 50% recurrence if they start before 1
year of age, to 10% if they start after age 3 years. Berg identified 4 risk factors for
recurrence of febrile seizures:
age of onset < 18 months
low fever < 102 degrees
brief duration of fever < 1 hour
family history of febrile seizures.
14% of children with no risk factors will recur, vs. a risk of 64% with with 3 or 4
risk factors [Berg]. |
| Epilepsy is uncommon after febrile seizures. |
Children with febrile seizures have only a 0.9% chance of
developing epilepsy (compared to 0.5% in the general population). Even children with a
risk factors such abnormal neurological status, complex febrile seizures, or family
history of epilepsy have only a 2-4% chance of developing epilepsy. |
| Febrile seizures are unlikely to cause mental retardation or
death. |
Even febrile status is associated with a 98% chance of no
identifiable long term neurological damage. [Shinnar] Other studies have shown a higher
incidence of neurological sequelae of febrile status up to 24% .[Van Esch] |
| Febrile status epilepticus has only a 3% chance of recurring
as status in a normal child. The risk rises to 1/3 for children with neurological
abnormalities. [Freeman].
|
Berg showed that children with 3-4 of the following risk
factors have a 72% chance of febrile status epilepticus recurring as status:
low fever <102
brief duration of fever < 1 hour
age < 18 months
family history of febrile seizures. [Berg]
|
Table 5.
Indication for rectal diazepam in febrile seizures
Commonly used indications:
May be offered to any child with febrile seizures.
Children with prolonged febrile seizures.
Children with multiple febrile seizures.
Children with high risk of recurrent seizures.
Dosage:
Diazepam diazepam 0.2 mg/kg per rectum (usual max. 5mg) prn seizure longer than 3
minutes.
Some authors recommend 0.3 to 0.5 mg/kg (not to exceed 10 mg) per rectum.
In children with high risk of recurrence, the use of rectal diazepam prn fever itself
may be appropriate.
Important points:
Parents must be carefully instructed on the use of rectal diazepam.
Lorazepam (Ativan (TM)) is not recommended rectally for status since it may take 45
minutes to be absorbed.
Diastat (TM) brand of rectal diazepam suppositories is FDA approved, although the
intravenous preparation of diazepam is often used "off label" via a TB syringe
with the needle off.
Sedation and rarely respiratory depression are possible side effects.
Table 6.
Indication for phenobarbital prophylaxis
in febrile seizures
Usual indications:
Neurologically abnormal children with prolonged febrile seizures.
Many practitioners would also prophylax neurologically normal children with prolonged
febrile seizures for several weeks to several months.
Rarely, children with multiple febrile seizures or with high risk of recurrent
seizures.
Dosage:
phenobarbital 5 mg/kg/day divided bid (starting dose not to exceed 90mg total per day)
Important points:
Phenobarbital given orally PRN seizures is not effective.
Most common side effects are hyperactivity, sedation, or rash.
__________________________
1AAP, "Practice Parameter: The Neurodiagnostic Evaluation of the Child with
a First Simple Febrile Seizure." Pediatrics 97 (5) 769-75. May 1996.
2Green S, "Can Seizures Be the Sole Manifestation of Meningitis in Febrile
Children?" Pediatrics. 92 (4) 527-34. Oct. 1993.
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