• A febrile
seizure, also known as a fever fit or febrile
convulsion, is a convulsion associated with a significant rise
in body temperature. They most commonly occur in children between the ages
of 6 months and 5 years of age. They are
more common in boys than girls.
• Since
early in the 20th century, people have debated about whether these children would
benefit from daily anticonvulsant therapy.
• Epidemiologic
studies have led to the division of febrile seizures into 3 groups, as follows:
– simple
febrile seizures,
– complex
febrile seizures, and
– symptomatic
febrile seizures.
v Simple
febrile seizure
• The
setting is fever in a child aged 6 months to 5 years.
• The
single seizure is generalized and lasts less than 15 minutes.
• The
child is otherwise neurologically healthy and without neurological abnormality
by examination or by developmental history.
• Fever
(and seizure) is not caused by meningitis, encephalitis, or other illness
affecting the brain.
• "Simple
febrile seizures" last <15 minutes, are generalized, and occur only
once per 24 hours.
v Complex
febrile seizure
• Age,
neurological status before the illness, and fever are the same as for simple
febrile seizure.
• This
seizure is either focal or prolonged (ie, ³15
min), or multiple seizures occur in close succession.
• "Complex
febrile seizures" last ³
15 minutes, have a focal onset, or occur more than once per 24 hours.
v Symptomatic
febrile seizure
• Age
and fever are the same as for simple febrile seizure.
• The
child has a preexisting neurological abnormality or acute illness.
CAUSES OF FEBRILE SEIZURES
• Infection — Febrile
seizures can occur as a result of the fever that accompanies bacterial or viral
infections, especially human herpesvirus-6 (also called roseola or sixth
disease).
• Immunizations — Fever
can occur as a side effect of certain vaccines, particularly after measles mumps
rubella (MMR) vaccination. The fever typically occurs 8 to 14 days after the
injection.
• Risk
factors — A family history of febrile seizures increases a
child's risk of febrile seizures.
Pathophysiology
• The
exact mechanism by which fever causes seizures is not known. But there are
various theories put forward to explain it.One theory states that respiratory
alkalosis which accompanies fever is the cause for seizures. Fever can cause
hyperventilation especially in children. This causes increase in the pH within
the brain. The increased pH increases the excitability and causes seizures.
This also explain why febrile seizures occur in children – they are more prone
for hyperventilation.Another theory states that increased temperature
causes down regulation of GABA ( gamma-aminobutyric acid ) a
receptors on the neuronal cell membrane. The inhibition of neuronal firing is
removed and this results in increased excitability an seizures.
Epidemiology
• Febrile
seizures occur in 2-5% of children aged 6 months to 5 years in industrialized
countries. Among children with febrile
seizures, about 70-75% have only simple febrile seizures, another 20-25% have
complex febrile seizures, and about 5% have symptomatic febrile seizures. Children
with a previous simple febrile seizure are at increased risk of recurrent
febrile seizures; this occurs in
approximately one third of cases. Children younger than 12 months at the time
of their first simple febrile seizure have a 50% probability of having a second
seizure. After 12 months, the probability decreases to 30%.Children who have
simple febrile seizures are at an increased risk for epilepsy. The rate of epilepsy by age 25 years is
approximately 2.4%, which is about twice the risk in the general population.The
literature does not support the hypothesis that simple febrile seizures lower
intelligence (ie, cause a learning disability) or are associated with increased
mortality .Sex: Males have a slightly (but definite) higher
incidence of febrile seizures.Age: Simple febrile seizures occur most
commonly in children aged 6 months to 5 years.
Clinical Presentation
• The
general approach the patient with febrile seizures is delineated in Figure 1.Each
child who presents with a febrile seizure requires a detailed history and a
thorough general and neurologic examination.These are the cornerstones of the
evaluation. Febrile seizures often occur in the context of otitis media,
roseola and human herpesvirus 6 (HHV6) infection, shigella, or similar
infections, making the evaluation more demanding. Several investigations need
to be considered.
• Children
with simple febrile seizures are neurologically and developmentally healthy
before and after the seizure.They do not experience a seizure in the absence of
fever.The seizure is described as either a generalized clonic or a generalized
tonic-clonic seizures.Signs of a focal seizure during the onset or in the
postictal period (eg, initial clonic movements of 1 limb or of the limbs on 1
side, a weak limb postictally) would rule out a simple febrile seizure.Similarly,
simple febrile seizure activity does not continue for more than 15 minutes,
although a postictal period of sleepiness or confusion can extend beyond the
15-minute maximum.Simple febrile seizures often occur with the initial
temperature elevation at the onset of illness. The seizure may be the first
indication that the child is ill. While no clear cutoff is known, a rectal
temperature under 38°C should raise concern that the event was not a simple
febrile seizure.
7.2- Physical Exam
• Physical
examination findings reveal a neurologically and developmentally healthy child.It
is especially important that the child have no signs of meningitis or
encephalitis (eg, stiff neck or persistent mental status changes).
Simple febrile seizures:
• are the most common. Typically, the child
loses consciousness and has a convulsion or rhythmic twitching of the arms or
legs.Most seizures do not last more than one to two minutes, although they can
last up to 15 minutes.After the seizure, the child may be confused or sleepy,
but does not have arm or leg weakness.
Complex febrile seizures
• are
less common and can last more than 15 minutes (or 30 minutes if in a series).The
child may have temporary weakness of an arm or a leg after the seizure
6.3- Laboratory Studies
• No
specific studies are indicated for a simple febrile seizure.Physicians should
focus on diagnosing the cause of fever.Other laboratory tests may be indicated
by the nature of the underlying febrile illness. For example, a child with
severe diarrhea may benefit from blood studies for electrolytes.
7.4-Lumbar Puncture (LP)
• LP
is recommended in children <12 mo of age after their first febrile seizure
to rule out meningitis.It is especially important to consider if the child has
received prior antibiotics that would mask the clinical symptoms of the
meningitis.The presence of an identified source of fever, such as otitis media,
does not eliminate the possibility of meningitis. Seizures are the major sign
of meningitis in 13-15% of children presenting with this disease, and 30-35% of
such children have no other meningeal signs.
7.4-Lumbar Puncture
• According
to the American Academy of Pediatrics (AAP) practice parameter, it is strongly
recommended in infants <1 yr of age because other signs of the
infection might not be present.A child between 12 and 18 mo of age should
also be considered for lumbar puncture because the clinical symptoms of
meningitis may be subtle in this age group. For the well-appearing child after
a febrile seizure, the yield of lumbar puncture is very low.For children
>18 mo of age, a lumbar puncture is indicated in the presence of clinical
signs and symptoms of meningitis (e.g., neck stiffness, Kernig sign, Brudzinski
sign) or if the history and/or physical examination otherwise suggest
intracranial infection.
7.5- Imaging Studies
• Neither
computed tomography (CT) nor magnetic resonance imaging (MRI) is indicated in
patients with simple febrile seizures.According to the AAP practice parameter,
a CT or MRI is not recommended in evaluating the child after a first simple
febrile seizure.
7.6- Other Tests
• EEG
is not indicated in children with simple febrile seizures. Published studies
demonstrate that the vast majority of these children have a normal EEG.In
addition, some of those with an abnormal EEG have remained free of seizures for
the duration of their follow-up. On the other hand, some of the children with a
normal initial EEG have experienced 1 or more afebrile seizures subsequent to
the EEG.Finally, no evidence indicates that beginning anticonvulsant therapy
for a child with simple febrile seizures and an abnormal EEG will alter the
child's eventual outcome.In general, antiepileptic therapy, continuous or
intermittent, is not recommended for children with one or more simple febrile
seizures. Parents should be counseled about the relative risks of recurrence of
febrile seizures and recurrence of epilepsy, educated on how to handle a
seizure acutely, and given emotional support.If the seizure lasts for
>5 min, then acute treatment with diazepam, lorazepam, or midazolam is
needed.Rectal diazepam is often prescribed to be given at the time of
recurrence of febrile seizure lasting >5 min:
–
<5ys: Rectal
0.5mg/kg
–
6-11 ys:
Rectal 0.3mg/kg
–
>12 ys:
0.2mg/kg
–
IV: 0.2-
0.5mg/kg
Some authors recommend 0.3 to
0.5 mg/kg (not to exceed 10 mg) per rectum.
Treatment
• If
the parents are very anxious concerning their child's seizures, intermittent
oral diazepam can be given during febrile illnesses (0.33 mg/kg every
8 hr during fever) to help reduce the risk of seizures in children known
to have had febrile seizures with previous illnesses. Intermittent oral
nitrazepam, clobazam, and clonazepam (0.1 mg/kg/day) have also been used.Other
therapies have included intermittent diazepam prophylaxis (0.5 mg/kg
administered as a rectal suppository every 8 hr), phenobarbital
(4-5 mg/kg/day in 1 or 2 divided doses), and valproate (20-30 mg/kg/day
in 2 or 3 divided doses).In the vast majority of cases it is not justified to
use these medications owing to the risk of side effects and lack of
demonstrated long-term benefits, even if the recurrence rate of febrile
seizures is expected to be decreased by these drugs.
• Antipyretics
can decrease the discomfort of the child but do not reduce the risk of having a
recurrent febrile seizure, probably because the seizure often occurs as the
temperature is rising or falling.
• Chronic
antiepileptic therapy may be considered for children with a high risk for
later epilepsy. Currently available data indicate that the possibility of
future epilepsy does not change with or without antiepileptic therapy.
• Iron
deficiency has been shown to be associated with an increased risk of
febrile seizures, and thus screening for that problem and treating it appears
appropriate.
RECURRENT FEBRILE SEIZURE
• Children
who have a febrile seizure are at risk for having another febrile seizure; this
occurs in approximately 30 to 35 percent of cases. Recurrent febrile seizures
do not necessarily occur at the same temperature as the first episode, and do
not occur every time the child has a fever. Most recurrences occur within one
year of the initial seizure and almost all occur within two years.
• The
risk of recurrent febrile seizures is higher for children who:
– Are
young (less than 15 months)
– Have
frequent fevers
– Have
a parent or sibling who had febrile seizures or epilepsy
– Have
a short time between the onset of fever and the seizure
– Had
a low degree of fever before their seizure
• Home
treatment — Parents who witness their child's febrile seizure
should take a number of steps to prevent the child from harming him or herself.Place
the child on their side but do not try to stop their movement or convulsions.
Do not put anything in the child's mouth.Keep an eye on a clock or watch.
Seizures that last for more than five minutes require immediate treatment. One
parent should stay with the child while another parent calls for emergency
medical assistance, available by dialing 911 in most areas of the United
States.Parents of a child who is at risk of having a recurrent febrile seizure
can be taught to give treatment at home for seizures that last longer than five
minutes. Treatment usually involves giving one dose of diazepam gel (Diastat®)
into the rectum. One dose is generally all that is required to stop a seizure.Preventive
treatment — In most cases, treatment to prevent future seizures
is not recommended; the risks and potential side effects of daily antiseizure
medications outweigh their benefit. In addition, giving medication (eg,
acetaminophen or ibuprofen) to prevent fever is not
recommended in a child without fever (eg, if the child has a cold but no fever)
because it does not appear to reduce the risk of future febrile seizures.Treatment
for fever (temperature greater than 100.4ºF or 38ºC) is acceptable but not
always required; parents should speak with their healthcare provider for help
in deciding when to treat a child's fever. Prognosis for normal neurologic
function is excellent.About one third of children who experience a single
simple febrile seizure will have another. The lifetime rate of epilepsy in
these children is slightly above that of the general population.A Danish
population-based study by Norgaard et al found little association between
febrile seizures and cognitive function. Data linked from health-care databases
and conscript records of Danish men born from 1977-1983 showed that, of the
18,276 eligible conscripts, 507 (2.8%) had a record of hospitalization with
febrile seizures and no known history of epilepsy. Compared with conscripts
with no record of febrile seizures, the adjusted prevalence ratio for having a
Boerge Prien intelligence test score in the bottom quartile was 1.08 (95%
confidence index [CI], 0.94-1.25). The adjusted prevalence ratios were 1.38
(95% CI, 1.07-1.79) for febrile seizures with an onset age of 3 months to <
1 year, 0.98 (95% CI, 0.80-1.18) for febrile seizures with an onset age of 1-2
years, and 1.14 (95% CI, 0.79-1.66) for an onset age of 3-5 years.
FOLLOW-UP
• Intelligence
and other aspects of brain development do not appear to be affected by a
febrile seizure, whether the seizure was simple, complex, or recurrent or
whether it occurred in the setting of infection or after immunization.Epilepsy
occurs more frequently in children who have had febrile seizures. However, the
risk that a child will develop epilepsy after a single, simple febrile seizure
is only slightly higher than that of a child who never has a febrile seizure.
