Simple vs. complex febrile seizures
A febrile seizure is defined by the International League Against Epilepsy
as "an epileptic seizure associated with a febrile illness not caused by an
infection of the central nervous system (CNS ), without previous neonatal
seizures or a previous unprovoked seizure, and not meeting criteria for other
acute symptomatic seizures."[2] Febrile seizures are classified as either simple
or complex.
Simple febrile seizures have the following features[3]:
- They are brief (lasting less than 15 minutes) and
resolve spontaneously.
- They typically occur as isolated events and not more
than once in 24 hours.
- They are characterized by generalized convulsions of the body.
In contrast, complex febrile seizures have 1 or more of the following
features[4]:
- They are prolonged (greater than 15 minutes) and may
not resolve spontaneously.
- They occur more than once in 24 hours during a
febrile illness.
- There is focal convulsion of 1 side of the body.
Epidemiology and risk factors
The incidence of simple febrile seizures is 2%–4% in children in
United States and
Western Europe.[5] They are most common between
the ages of 6 months and 5 years, and have a peak incidence at 18 months of age.
Timing of fever with respect to seizure onset can be variable. Studies have
found that while the majority (57%) of children experience a seizure 1–24 hours
after fever onset, children can also have a seizure either prior to or more than
24 hours after the onset of fever.[6,7]
There is convincing evidence for a genetic basis for febrile seizures,
with 24%–40% of patients reporting a positive family history.[8] There is a
higher concordance rate among monozygotic than dizygotic twins.[3] The mode of
inheritance may be multifactorial. Susceptibility foci for febrile seizures have
been identified on chromosomes 2, 5, 6, 8, 18 and 19.[9]
Risk factors associated with experiencing a first simple febrile seizure
include[3,10]:
- First or second degree relative with a history of
febrile convulsions
- Developmental delay
- Day care attendance
- V iral infections (eg, influenza A, human herpesvirus
6)
- Vaccinations (eg, DTaP and MMR)
After a first simple febrile seizure, approximately 30% of children will
have a recurrence and 10% will have 3 or more febrile convulsions.[3]
Risk factors associated with recurrence include[3,10]:
- Family history of febrile seizures
- O nset of simple febrile seizures at less than 12
months of age
- Temperature at less than 40 C
Aside from a high rate of recurrence, simple febrile seizures have not
been shown to place children at risk for long-term complications.[1] Studies
have not identified cognitive declines, lower school performance, attention
difficulties, nor behavioral abnormalities as an outcome of recurrent simple
febrile seizures. There are no reports of death as a result of a simple febrile
seizure.
The risk of developing epilepsy after a single simple febrile seizure is
not substantially different than the risk in the general population. Features
associated with an increased risk include[1,3]:
- Family history of epilepsy
- Occurrence of complex febrile seizure
- Occurrence of multiple simple febrile seizures
- O nset of simple febrile seizures at less than 12 months of age
Evaluation
In order to make a diagnosis of simple febrile seizure, other provocative
etiologies such as electrolyte imbalance and primary neurological insults
(meningitis or encephalitis) must be excluded. A detailed history and physical
examination can aid in eliminating other causes for a child's seizure. A
practice parameter has been issued by the American Academy of Pediatrics (AAP) for evaluation
of a child between the ages of 6 months and 5 years who presents within 12 hours
of the first simple febrile seizure.[11] Routine blood work including serum
electrolytes, calcium, phosphorous, magnesium, complete blood count or blood
glucose are of limited value in the absence of a suspicious history (eg,
vomiting) or physical examination (eg, suggestive of dehydration). Laboratory
work should be directed towards identifying the source of fever rather than
evaluating the seizure.[11]
The AAP evaluation guidelines recommend that a lumbar puncture be
strongly considered in infants less than 12 months of age. Lumbar puncture
should be considered in children between 12 and 18 months of age because
clinical signs of meningitis may be subtle. In children older than 18 months,
lumbar puncture is recommended in the presence of history or physical
examination findings suggesting intracranial infection. A lumbar puncture is
recommended after a first complex febrile seizure, in a child with persistent
lethargy, and in a child who has received prior antibiotic
treatment.[11]
Electroencephalograms (EE Gs) are not recommended in the evaluation of a
neurologically healthy child after a first febrile seizure. EE Gs are more
likely to be abnormal in children with complex febrile seizure or children with
family history of febrile seizures. However, EEG abnormalities are not
predictive of the recurrence of febrile seizures or development of epilepsy.[3]
The AAP does not recommend neuroimaging in the form of computed tomography or
magnetic resonance imaging scans in the evaluation of children with simple
febrile seizure.[11]
Treatment
Simple febrile seizures are brief and self-resolving and no intervention
is usually necessary. Persistent seizure activity upon arrival to the Emergency
Department warrants therapeutic intervention since typically, this seizure
activity has been continuing for longer than 15 minutes. This type of prolonged
seizure would no longer be categorized as a simple febrile seizure. Intravenous
diazepam or lorazepam or rectal diazepam can be used as the first line
medication.[3] Persistence of seizure activity warrants initiation of full
status epilepticus protocol.
Since the major risk after simple febrile seizures is recurrence,
numerous studies have evaluated the use of antipyretic and anticonvulsant drugs
for preventing febrile seizures. No study has demonstrated that antipyretics
(aspirin, acetaminophen or ibuprofen), in the absence of anti-convulsant drugs
reduce the recurrence risk of febrile seizures.[12,13]
The role of anticonvulsant drugs including phenobarbital, valproic acid,
carbamazepine, phenytoin and diazepam in preventing recurrent febrile seizures
has been studied.[1,14] Phenobarbital, valproic acid, and intermittent diazepam
administration have all been shown to reduce the recurrence of subsequent
febrile seizures.[1,14] Carbamazepine and phenytoin have not been shown to be
effective in preventing the recurrence of febrile seizures.
However, anti-convulsants have significant side-effects and toxicities[1]
(Table 1) and there is no evidence that prevention of febrile seizures reduces
the risk of developing subsequent epilepsy.[3] There is also no evidence that
links simple febrile seizures to development of cognitive disabilities or
premature death. Thus, the AAP does not recommend the use of continuous or
intermittent antiepileptic therapy, given that the potential toxicities
associated with these medications outweigh the relatively minor risks posed by
simple febrile seizures.[1,14]
Counseling
After a child experiences a simple febrile seizure, parents can feel
anxious and frightened by this episode. During the episode, they may feel
helpless as they are unable to stop the seizure. They may worry that the child
will die during the convulsion or that the child may suffer neurological injury
secondary to the simple febrile seizure. In these situations, physician
reassurance and parental education are very important. Basic facts about simple
febrile seizures and how to keep a child safe during an episode should be
presented to the family. Specific information on management of seizures should
be discussed including when to take the child to the Emergency Department or
call the physician's office.
Conclusion
Simple febrile seizures are a common type of childhood seizures. When
evaluating a child, diagnostic studies should be aimed at exploring the cause of
fever as clinically indicated. Given the generally favorable prognosis
associated with simple febrile seizures, anticonvulsant therapy is not
indicated. Counseling and parental education are important to attempt to reduce
parental anxiety.
References
[1.] American Academy of Pediatrics: Steering Committee
on Quality Improvement and Management, Subcommittee on Febrile Seizures. Febrile
seizures: Clinical practice guideline for the long-term management of the child
with simple febrile seizures. Pediatrics 2008;121:1281-1286.
[2.] Commission on Epidemiology and Prognosis, International League
Against Epilepsy. Guidelines for epidemiologic studies on epilepsy. Epilepsia
1993;34:592-596.
[3.] Shinnar S, Glauser TA. Febrile Seizures. J Child Neurol
2002;17:S44-S52.
[4.] Berg AT, Shinnar S. Complex febrile seizures. Epilepsia
1996;37:126-133.
[5.] Verity CM, Butler NR, Golding J. Febrile convulsions in a national
cohort followed up from birth. I. Prevalence and recurrence in the first 5 years
of life. BMJ 1985;290:1307-1315.
[6.] Berg AT, Shinnar S, Hauser WA, et
al. Predictors of recurrent febrile seizures: A prospective study of the
circumstances surrounding the initial febrile seizure. N Engl J Med
1992;327:1122-1127.
[7.] Berg AT, Shinnar S, Darefsky AS,
et al. Predictors of recurrent febrile seizures. Arch Pediatr Adolesc Med
1997;151:371-378.
[8.] Hauser WA, Annegers JF,
Andersen VE, Kurland LT. The risk of seizure
disorders among relatives of children with febrile convulsions. Neurology
1985;35(9):1268-1273.
[9.] Nakayama J, Arinami T. Molecular genetics of febrile seizures.
Epilepsy Research 2006;S190-S198.
[10.] Jones T, Jacobsen SJ. Childhood febrile seizures: Overview and
implications. Int J Med Sci 2007;4(2):110-114.
[11.] American Academy of Pediatrics: Provisional
Committee on Quality Improvement. Practice parameter: The neurodiagnostic
evaluation of the child with a simple febrile seizure. Pediatrics
1996;97:769-775.
[12.] Camfield PR, Camfield CS, Shapiro S, et al. The first febrile
seizure — Antipyretic instruction plus either phenobarbital or placebo to
prevent a recurrence. J Pediatr 1980;97:16-21.
[13.] van Stuijvenberg M, Derksen-Lubsen G et al. Randomized, controlled
trial of Ibuprofen syrup administered during febrile illness to prevent febrile
seizure recurrences. Pediatrics 1998;102;e51.
[14.] Baumann RJ, Duffner PK. Treatment of children with simple febrile
seizures: The AAP Practice Parameter. Pediatric Neurol 2000;23:11-17. | 
