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According to the World Health Organization, status epilepticus (SE)
is defined as seizures that are sufficiently frequent or prolonged
to produce an “enduring epileptic condition.”1 Implicit
in this definition is the concept that the event’s duration renders
it physiologically distinct from other seizure types and, therefore,
it requires specialized workup and management.
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Although there is no well-determined absolute duration beyond
which a prolonged seizure is definitively distinct from shorter
ones, in practice SE is defined as continuous seizures, or a cluster
of seizures without return to consciousness, lasting 30 minutes
or more. With this definition, the incidence of SE in children approximates
18 to 38 per 100,000 persons/year.2 More than
40% of SE cases occur in children younger than 2 years
of age.3
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A reasonable and more inclusive definition of SE takes into account
observations that individual seizures rarely last longer than 5
minutes, and that in clinical practice seizures longer than 5 minutes
are often treated acutely. Accordingly, there is a trend toward
reducing the duration required for diagnosis of SE, with some reports
defining minimal SE duration as 5, 10, or 20 minutes; incidence
of SE by these definitions has not been extensively studied.4
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The recent trend toward reducing seizure duration in the definition
of SE is supported by clinical and experimental data. For instance,
Shinnar and colleagues found a bimodal distribution of new-onset
seizure durations in children clustered around 2 means: 3.6 minutes (76% of
cases), and 31 minutes (24% of cases).5 This
corroborates the observation that seizures lasting longer than 5
minutes are likely to continue for at least several minutes longer,
and fits well with the widely accepted practice to administer anticonvulsants
acutely for seizures lasting 5 minutes or more. The rationale for
earlier treatment of SE is also supported by data from animal seizure
models that show loss and dysfunction of GABAA receptors
and reduced sensitivity to benzodiazepines after prolonged seizures
in rats.6-9
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Numerous seizure types, if prolonged, can comprise SE. With some
overlap, these can be divided into convulsive and nonconvulsive
subgroups. Prolonged primary or secondary generalized tonic-clonic
seizures, including febrile seizures, are the most common form of
convulsive SE in children.
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Nonconvulsive SE (NCSE) is a relatively heterogenous group of
disorders.11 The clinical picture is often that
of depressed consciousness ranging from confusion to coma. Particularly
in the intensive care unit (ICU), NCSE is now becoming more widely
recognized, in part due to increased use of electroencephalogram
(EEG) monitoring. In a recent report, EEG ordered to evaluate unresponsiveness
in the pediatric ICU showed a pattern consistent with NCSE in 33% of 178
cases.12 Prolonged absence seizures (absence status)
are also a form of NCSE characterized by altered consciousness,
at times lasting hours until the diagnosis is made by EEG. Another
form of NCSE, one in which consciousness is typically ...