Causes of SE and associated risk
SE is classified according to etiology. Definitions of common types of SE
are presented in Table 1. Acute symptomatic SE, which is SE caused by an acute
central nervous system (CNS) insult, poses the highest risk for mortality and
morbidity. This type of SE may occur during meningitis, encephalitis,
electrolyte disturbance, sepsis, hypoxia, trauma, or intoxication.
Increased long term risk of mesial temporal sclerosis is associated with
febrile SE, which is SE provoked by a febrile illness (eg, upper respiratory
infection, sinusitis), excluding direct CNS infection (eg, meningitis or
encephalitis). Febrile SE involves seizures in response to fever in children as
a result of genetic susceptibility.
Remote symptomatic SE may occur in patients with chronic encephalopathy
without an acute provocation and may involve a previous traumatic brain injury,
a chromosomal disorder, or CNS malformation. SE in children with known epilepsy
carries a lower risk of morbidity and mortality. Risk is increased in cases with
previous neurological injury and new onset seizures. A first seizure in children
who are experiencing SE without a definable cause (ie, cryptogenic SE), however,
poses a lower risk.
New recommendations
Prior to the 2006 practice parameter, specific guidelines for diagnostic
assessment of SE in children were not available. Earlier consensus based
guidelines addressed initial treatment of SE for adults and children,[2] but
provided limited recommendations on evaluation of SE causes. Identifying
specific etiology of SE is important, since specific treatment may be needed in
addition to anticonvulsant therapy.
The new practice parameter includes evidence based recommendations on the
following diagnostic tests for children with SE: blood culture and lumbar
puncture (LP), antiepileptic drug (AED) levels, toxicology screening, metabolic
and genetic studies, EEG, and computed tomography (CT) or magnetic resonance
imaging (MRI) studies. The new practice parameter does not offer recommendations
on the complete blood count (CBC) and chemistry profiles (glucose, sodium,
calcium, magnesium, and blood urea nitrogen), since these tests are now
routinely obtained in children with SE. The practice parameter also does not
address evaluation of neonatal seizures, febrile SE, and refractory
SE.
Blood cultures and LP
Infectious illnesses, such as meningitis or encephalitis, may trigger
seizures by directly affecting CNS, or the brain may be affected by systemic
involvement. In pre-existing epilepsy, a systemic illness also may lower the
seizure threshold.
The recommendations support the common practice of obtaining blood
cultures when infection is clinically suspected, and performing LP when a CNS
infection is suspected, especially in cases of pediatric SE with fever. However,
the practice parameter authors conclude that available data are insufficient to
support or refute the routine need for these tests.
AED levels
SE in children with epilepsy treated with AEDs may occur when AED levels
are too low. Based on the available data, the authors conclude that checking AED
levels should be considered in children with SE who take these
medications.
Toxicology testing
Review of studies found that toxic ingestion was diagnosed in at least
3.6% of children presenting with SE, which was considered sufficiently high.
Since determining this diagnosis is critical to prompt treatment, the authors
recommend that toxicology testing may be considered in cases when SE etiology is
not immediately apparent.
The authors also caution that a routine urine toxicology screening will
only detect drugs of abuse. If a specific toxin is suspected, such as
theophylline, lindane, carbamazepine, or chemotherapy, a specific serum
toxicology level is needed.
Metabolic and genetic testing
Seizures may be caused by inborn errors of metabolism (IEM), such as
disorders of amino acid, ammonia, and organic acid metabolism, as well as
disorders involving mitochondrial and peroxisomal functions. When SE etiology
cannot be established through initial evaluation, IEM studies may be considered,
particularly in children with historic features that suggest a metabolic
disorder (see Table 2). Specific metabolic studies should be guided by the
history and clinical examination. Due to insufficient evidence, the
recommendations could not support or refute performing IEM studies on a routine
basis.
Although specific chromosomal or genetic disorders also may cause SE,
data are not available to recommend or refute routine chromosomal or molecular
testing in children with SE.
EEG
An EEG performed during SE can establish whether the abnormalities are
focal or generalized. Since this distinction affects treatment choices, and
studies found EEG abnormalities in 62% of children with SE, the authors conclude
that EEG may be considered in children with new onset SE.
An EEG also may be considered when pseudostatus epilepticus is suspected,
which is a nonepileptic event that resembles SE. In data reviewed, 21% of
children originally believed to have convulsive SE had
pseudoseizures.
An EEG also can identify nonconvulsive status epilepticus (NCSE), which
is electrographic SE with altered awareness that may occur with or without overt
clinical signs. NCSE may be found in children after convulsive SE is controlled,
although data on specifically pediatric prevalence of NCSE are not available.
For this reason, recommendations could not be made on whether routine EEG would
be useful to demonstrate NCSE.
Neuroimaging studies
CT or MRI can demonstrate the structural abnormalities causing SE, and
may be considered in children with SE if clinically indicated or if the etiology
is unclear. The child must be stabilized and SE controlled before neuroimaging
studies are performed. Data were insufficient, however, to recommend routine use
of neuroimaging in evaluating children with SE.
Neuroimaging can be used to exclude the need for neurosurgery in children
with new onset SE who do not have prior history of epilepsy, and in cases with
SE that is unresponsive to treatment. Neuroimaging also can show transient focal
changes, as well as changes that are secondary to a focal seizure, which helps
to identify the origin of the focus (see Figure 1). Although MRI is more
sensitive, CT generally is more easily available in emergencies.
Conclusion
The new evidence-based recommendations reinforce the need for immediate
clinical evaluation to determine the specific etiology of SE in children, in
order to provide appropriate treatment as quickly as possible. It is especially
critical to rapidly identify SE caused by an acute treatable CNS insult, which
may occur during meningitis or encephalitis, since this etiology poses the
highest risk for mortality and morbidity. Future prospective studies will be
needed to establish the factors that may precipitate SE in children, as well as
the value of various diagnostic studies in guiding treatment
decisions.
REFERENCES
[1.] Riviello JJ Jr, Ashwal S, Hirtz D, et al. Practice Parameter:
Diagnostic assessment of the child with status epilepticus (an evidence based
review): Report of the Quality Standards Subcommittee of the American Academy of
Neurology and the Practice Committee of the Child Neurology Society. Neurology
2006;67:1542-1550.
[2.] Dodson WE, DeLorenzo RJ, Pedley TA, et al. The treatment of
convulsive status epilepticus: Recommendations of the Epilepsy Foundation of
America's Working Group on Status Epilepticus. JAMA 1993;270:854-859. | 
