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AASM Membership Sections Newsletter
■
Issue #6
The patient and family returned to the
sleep clinic 2 years later at the age of 10 years
and now had concerns of seizure activity
and persistent daytime sleepiness. The family
was prompted to return for a neurological
evaluation after teachers reported that the
patient had frequent staring spells and
head drops. Parents still reported excessive
daytime sleepiness (modified ESS 19/24),
snoring and frequent “kicking at night”.
The patient was now sleeping with parents
because he would commonly report that
he saw a stranger outside his own room as
he was falling asleep, a likely hypnogogic
hallucination, and woke more during the
night. He denied sleep paralysis, dream
enactment and nightmares but did report
vivid dreams. Father did note that the patient
would bob head up and down without any
clear precipitant and that this had been
present for over 2 years. The father believed
this to be a manifestation of the sleepiness.
On further questioning, the patient recalled
isolated instances in the last one year when
he had to sit down with laughter because
he felt weak in the legs. Medication: MVI
with iron. Exam was notable for obesity
BMI 37.7 kg/m2 but otherwise unchanged.
No evidence of precocious puberty noted.
A repeat PSG and MSLT were ordered for
evaluation of narcolepsy. The patient was
positive for HLA DQB1*06:02 and negative
for HLA DRB1*1501 haplotypes.
A repeat PSG was ordered (April 2014)
and was again notable for a short sleep
latency of 5 minutes and REM onset latency
of 2 minutes (Figure 2a). Sleep efficiency was
mildly reduced compared to prior at 90%
and reported WASO increased to 58 minutes.
Sleep architecture reflected some changes
since last study with less N3 sleep and more
REM sleep: 17% N1 sleep, 42% N2, 14% N3,
and 27% REM. Arousal index was 11/hour.
Total RDI was 1/hour and no evidence of gas
exchange abnormalities. Again, a periodic
limb movement index was noted at 29/hour
(4/hour associated with arousals). Ferritin
level was 43 ng/ml. MSLT results revealed a
mean sleep latency of 4.7 minutes and four
sleep-onset REM periods (Figure 2b).
Outcome:
The patient was diagnosed with
narcolepsy with cataplexy (narcolepsy type
1). The parents refused medication treatment
and he is currently managed with scheduled
naps. Academically, he is doing well but
still has an ESS of 18/24 and mild cataplexy
occurring daily.
Discussion:
The diagnosis of narcolepsy
type 1 can be challenging in a pediatric
population given the presence of atypical
cataplexy, staggered presentation of core
narcolepsy symptoms, co-morbidities of
narcolepsy that may lead to alternative
diagnoses and the difficulty in obtaining
an accurate history with pediatric patients
who may not be able to understand or
describe symptoms in detail. Such features
may contribute to the well documented
discordance between age of diagnosis and
symptom onset
1
which has been reported
to range between 1-60 years, with a median
of 10.5 years
2
. Certainly, this case highlights
these diagnostic challenges and we discuss
these issues in more detail below.
While cataplexy is generally precipitated
by strong emotions such as laughter, children
with narcolepsy type 1 have been reported
to present early in the disease course with
facial or generalized hypotonia, droopy
eyelids, jaw slackening (with and without
tongue protrusion) and/or gait unsteadiness;
these manifestations of hypotonia are not
related to emotion
3
. Furthermore, facial
movements may occur that mimic motor
tics or dyskinesias. In retrospect, the
family reports “head bobbing” (without
precipitant) close to the onset of excessive
daytime sleepiness (EDS). A year later he
reported the development of more classic
cataplexy symptoms with bilateral leg
weakness associated with laughter. Such
staged presentation of cataplexy symptoms
exemplifies the rostral to caudal trajectory
of cataplexy development that affects axial
structures
4
,
5
.
Though excessive daytime sleepiness is
almost always one of the first presenting
symptoms of narcolepsy, the true incidence
of REM-related core characteristics
of narcolepsy such as hypnogogic
hallucinations, sleep paralysis and cataplexy
are unclear in the pediatric population.
One study estimated the incidence of
hypnogogic hallucinations as 39% and sleep
paralysis as 29% in a clinical population
6
.
The incidence of cataplexy varies in studies
including children ranging from 40-80%
6
,
7
.
Furthermore, core narcolepsy symptoms may
appear years after the initial presentation of
excessive daytime sleepiness contributing to
diagnostic challenges
8
. In our patient, more
classic cataplexy triggered by emotion and
more recently described nocturnal sleep
disturbances associated with the narcolepsy
9
developed almost 2 years after the first sleep
study evaluation.
Commonly reported co-morbidities
with narcolepsy in children include rapid
onset weight gain
10
, precocious puberty
11
,
REM behavior disorder
12
and periodic limb
movements of sleep
13
. Even more relevant
to our case is a recent report that sleep
disordered breathing and periodic limb
movements of sleep are highly prevalent
among patients with narcolepsy type 1,
14
suggesting that a differential diagnosis should
still include narcolepsy in the setting of a
child with excessive daytime sleepiness and
evidence of other sleep disorders.
What was helpful in this case was the
finding of a nocturnal REM onset period
in the first and second polysomnograms.
A nocturnal sleep onset REM period
(SOREMP) is defined as a REM period ≤ 15
min from sleep onset and is now permitted
to count towards one of the two required
SOREMPS on PSG and MSLT in the ICSD
3 manual
15
. A nocturnal SOREMP is highly
specific to narcolepsy with cataplexy
16
with a
reported high specificity of 95.4 % ; 95% CI
(90.4-98.3%) in a large clinical population
though sensitivity was low (57.4%; 95%
