The Turkish Journal of Pediatrics
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Nonconvulsive status epilepticus during childhood: clinical and electroencephalographic features
Yüksel Yılmaz, Oğuzhan Onultan, Mustafa Berber
Division of Child Neurology, Department of Pediatrics, Marmara University Faculty of Medicine, İstanbul, Turkey
|Yılmaz Y, Onultan O, Berber M. Nonconvulsive status epilepticus
during childhood: clinical and electroencephalographic features. Turk J Pediatr
2008; 50: 449-455.
Nonconvulsive status epilepticus (NCSE) is a medical emergency, which
is diagnosed most frequently with the routine use of EEG in the pediatric
emergency and intensive care units.
Data from eight patients, ranging from 2.8-15 years old (median 8.7 years),
treated with the diagnosis of NCSE were evaluated on clinical basis. The
patients attended the hospital with acute confusional state ranging from
sudden onset of verbal cooperation insufficiency to aimless-meaningless
behavior and confusion without any motor component of seizure. While five
of the cases were diagnosed and followed up with epilepsy, the other three
had no history of epilepsy. No reason was detected that could cause acute
encephalopathy. EEG examinations during acute confusional state showed
partial or generalized continuous electrographic seizure activity lasting at
least 30 minutes without clinical seizure activity. After administration of
intravenous antiepileptic medication, the confusional states of the patients
recovered, and the EEG examinations showed normal baseline activity with
significantly diminished discharges or complete normal waveform.
Nonconvulsive status epilepticus should be considered in all children admitted
to the hospital with acute unexplained encephalopathy, whether they have a
history of epilepsy or not. Emergent EEG examination should be a routine part
of evaluation in these children for the diagnosis and treatment of NCSE.
nonconvulsive status epilepticus, childhood.
|Nonconvulsive status epilepticus (NCSE),
characterized by a cognitive or behavioral
change that lasts for at least 30 minutes with
electroencephalographic (EEG) evidence of
seizures, is a medical emergency, which is
diagnosed most frequently with extensive use
of EEG in the pediatric emergency and intensive
care units[1-4]. However, the diagnostic criteria,
classification, EEG findings and treatment
strategies are controversial[2,5-7]. We report the
clinical findings of eight children treated with
the diagnosis of NCSE, and aim to discuss the
clinical importance of NCSE during childhood.|
|Material and Methods |
|Eight patients, aged between 2.8-15 years
(median 8.7 years), admitted to the pediatric
emergency unit between April 1999 - January
2004 with acute alteration of consciousness for
a minimum of 30 minutes, ranging from lack
of verbal cooperation to coma associated with
or without behavior change, and unattributable
to any etiology, were evaluated. A detailed
history including epileptic symptomatology
was taken; thorough physical and neurological
examinations were performed. Any potential
causes of an acute encephalopathy, including
intoxication, acute metabolic and infectious
etiologies, and any possible causes of acute
cerebral damage, were all considered in the
differential diagnosis and eliminated.
The EEG recordings were performed during and
after an intravenous anticonvulsant medication
with a 14-channel electroencephalogram (Nihon
Cohden) using the International 10-20 system
of electrode placement and clinical follow-up
was done. NCSE was described as “acute
confusional state at the time of EEG discharges
consistent with electrophysiological status
lasting more than 30 minutes, which were abated
with intravenous antiepileptic medication”.
Standard dose intravenous anticonvulsant drugs
including diazepam, midazolam, phenobarbital
(PB) and diphenylhydantoin (DPH) were
selected based on the clinical and EEG findings.
The clinical features and electrophysiological
findings of the patients were evaluated.
|The clinical and ictal EEG findings of patients
are presented in Table I. The patients presented
with an acute onset of consciousness change
ranging from lack of verbal cooperation to coma
(n: 7) or bizarre, purposeless behavior despite
the ability of limited verbal communication
(n: 1). None of the patients had convulsive
seizure before the onset of these clinical
findings. Motor component consistent with
convulsion was not observed. Three patients
did not have a previous history of seizure;
the other five patients had been treated with
the diagnosis of epilepsy. The EEG recordings
of the patients revealed generalized (n: 1)
or predominant in particular areas (n: 7)
continuous slow wave, and spike-and-slow
wave discharges with high amplitude. After
the administration of intravenous medication,
the consciousness and behavior change of
the patients resolved and the EEG findings
normalized or discharges were significantly
diminished within 30 minutes (Figs. 1, 2).
| ||Fig. 1. EEG examination of patient no. 6 (A: Ictal EEG before intravenous antiepileptic drug (IV AED) showed
generalized 3-3.5 Hz spike and wave discharges especially prominent on frontal areas with some irregularly shaped
waveform and fragmentations; B: After IV AED therapy).|
| ||Fig. 2. EEG examination of patient no. 7 (A: Ictal EEG
before intravenous antiepileptic drug (IV AED) revealed
asymmetry with prominent delta waves on left hemisphere
and continuous sharp and spike wave discharges on right
hemisphere; B: After IV AED therapy).|
| ||Table I. Clinical and EEG Findings of the Patients|
|Status epilepticus (SE) is “longer than 30
minutes of continuous seizure activity or
two or more sequential seizures without full
recovery of consciousness between the seizure”,
and SE is divided into convulsive SE and
NCSE[2,8]. NCSE is defined as “the presence of
seizure activity on EEG associated with changes
of consciousness and/or behavior without
convulsive movements and often showing a good
response to anticonvulsant medication”, but the
definition and diagnostic criteria differ between
some authors[2,3,9-11]. According to Kaplan, NCSE
is “an epileptic state in which there is some
impairment of consciousness associated with
ongoing seizure activity on EEG”. The current
definition reported by Kaplan is “multiple
seizures or continuous seizure activity on
EEG with a nonconvulsive clinical correlate
(typically cognitive or behavioral change with
minor facial myoclonus unaccompanied by
frank convulsive movements) without return
to baseline state”.
There is a clear overlap of encephalopathies
with different etiologies; patients with
metabolic, infectious, toxic encephalopathies
and acute cerebral injury also show the same
or a very similar clinical picture considering
consciousness and EEG findings, including
partial or generalized continuous epileptiform
discharges[12-14]. However, as Kaplan indicated,
NCSE should be considered as an epileptic
state. The patients with metabolic, toxic
or infectious encephalopathies and acute
intracranial pathologies were not included in
this series. The mainstay of our study was to
consider NCSE as a differential diagnosis in
patients with encephalopathy that is not caused
by any metabolic or infectious or another
identifiable etiology. Although these etiologies
readily show a similar clinical picture and EEG
patterns, the underlying cause of change in
consciousness is difficult to claim, whether
a result of the underlying cause or a result
of the electrophysiological discharges. The
diagnosis of NCSE is difficult in some cases
because there are no specific clinical features
or laboratory test other than EEG examination.
For the accurate diagnosis, the presence of
seizure activity on EEG in addition to variable
clinical findings without convulsive movements
should be demonstrated[1,2].
The real incidence of NCSE is unknown and
it is accepted that NCSE is an underestimated
clinical entity due to failure to diagnose[1,3,4,15].
Another problem in determining the incidence
is the confusion regarding its definition.
It is postulated that 25% of patients who
experience SE have NCSE, either absence or
complex partial SE[3,16]. In the study of Towne
et al., which was conducted in unselected
comatose patients, NCSE was found as an
under-recognized cause of coma, occurring in
8% of all comatose patients without signs of
seizure activity. Alehan et al. investigated the
role of EEG in the pediatric emergency unit,
and reported that seven patients of a total of
56 children with new-onset seizures or known
epilepsy presenting with worsening seizures
and altered mentation or with acute confusional
states were diagnosed as NCSE. Saengpattrachai
et al. reported that the diagnosis of NCSE
was made in 23 of 141 children with an
unexplained decrease in level of consciousness
and no overt clinical seizures.
Nonconvulsive status epilepticus may be the
first seizure in healthy children without a
history of epilepsy; on the other hand, epileptic
children may present NCSE with or without
any preceding factor[2,3,9,18]. Three of our eight
patients had no previous history of seizure,
whereas five of them had been treated with
the diagnosis of epilepsy; three of these five
patients had symptomatic epilepsy (Sturge-
Weber syndrome, operated brain tumor and
focal cortical dysplasia), whereas the etiology of
epilepsy was unknown in the other two patients.
NCSE may occur as both generalized and partial
epilepsies, similarly both in symptomatic and
Clinical findings of NCSE are quite variable during
childhood; children with NCSE may be admitted
to the emergency units because of strange
behavior, acute confusional state, or coma[3,9]. One
of our patients (patient number 6) presented with
only bizarre behaviors, meaningless talking and
laughing, but she could obey simple commands
and limited verbal communication was possible.
The other seven patients were non-cooperative,
ranging from mild-moderate confusional state
to coma. Current pediatric emergency practice
for a confused child includes investigations to
detect any metabolic, toxic or infectious etiology,
as well as intracranial pathologies. Children
admitted to the hospital with acute, unexplained
consciousness or behavior change, with or
without a history or diagnosis of epilepsy,
should be evaluated by EEG for the diagnosis
and treatment of NCSE. Emergent EEG was
defined as any EEG examination requested for
immediate performance during non-business
hours or any EEG done to exclude NCSE with
24-hours-a-day, 7-days-a-week availability and
after approval by the neurology or neurosurgery
services[19-21]. The role of emergent EEG has
been studied both for adults and children[4,19,22].
EEG monitoring has been an inevitable part
of pediatric intensive units. We believe
that emergent EEG examination should be
a part of diagnostic studies in the pediatric
The EEG findings of NCSE are heterogeneous;
generalized or focal (temporal, temporo-frontal)
spike-and-slow wave complexes, polyspike
discharges, irregular sharp or slow waves
may be seen[2,3]. Classification of NCSE is
not yet clear[3,5,6]. Previously, NCSE has been
generally divided into two types: absence SE
and complex partial SE. With the advent
of electrophysiological and neuroradiological
methods, new classification schemes have been
proposed. According to Kaplan, NCSE may
be classified as
1) localization-related NCSE,
2) generalized NCSE, and
or intermediate NCSE.
(localization-related) NCSE has been classified
based on the localization of epileptic discharges
as NCSE of temporal origin and NCSE of
extratemporal origin, and electroclinical varieties
of NCSE subtypes have been reported. The
accurate subclassification of NCSE can be
difficult, not only in children without previous
diagnosis of epilepsy but also in patients
with localization-related epilepsy. Emergent
EEG examinations of seven of our eight
patients revealed epileptic discharges with
focal dominance, whereas only one patient
had bilateral synchronous discharges. Based
on the emergent EEG findings, we could not
make thorough sub-classification of NCSE free
of any doubt. Clinical data including types
of new seizures obtained during a long-term
follow-up period, as well as ictal and interictal
video EEG monitoring may be helpful for the
The therapy regimens of NCSE are controversial;
benzodiazepines, DPH and PB are believed to
be effective[3,12,25-27]. Midazolam, propofol, and
topiramate have been found as effective in
patients with refractory status epilepticus[25,28,29].
In our series, diazepam was selected as the drug
of first choice in six patients, but clinical and
EEG findings disappeared only in one patient.
In four patients unresponsive to diazepam, PB
or DPH had to be administered as second drug,
and in four patients, midazolam was used as
third anticonvulsant. Our experiences do not
allow us to propose the drug of first choice;
however, it should be taken into consideration
that diazepam might not be effective as the
first choice in the treatment of NCSE.
The prognosis of NCSE is still inconclusive[30-34].
A few basic scientific studies demons-trated
that NCSE may produce long-term behavioral
deficits and functional changes in neurons
that alter electrical excitability in neuronal
circuits despite the absence of neuronal
damage[35,36]. Recently, persistent abnormality
on magnetic resonance imaging after NCSE was
reported. The outcome from de novo NCSE
in ambulatory patients has not been studied
in detail. All children with NCSE should be
followed carefully, since the data collected to
the present is not satisfactory.
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