Clinical commentary with video sequences
Epileptic Disord 2009; 11 (1): 90-4

Copyright © 2019 John Libbey Eurotext. Téléchargé par NYU LANGONE MED CTR SCH OF MED HEALTH SCIENCES LIBRARY le 11/04/2019.

Electrophysiological
characterisation of myoclonicatonic seizures in symptomatic
continuous spike-waves during
slow sleep syndrome
Pascal Vrielynck1,2, Pierre Defresne3
1

Service de neurologie, Hôpital de Jolimont, Haine Saint-Paul, Belgium
Centre neurologique William Lennox, Université Catholique de Louvain, Ottignies LLN,
Belgium
3
Service de pédiatrie, Hôpital de Jolimont, Haine Saint-Paul, Belgium
2

Received February 19, 2008; Accepted February 17, 2009

ABSTRACT – Sudden epileptic falls are frequently reported in continuous spikewaves during slow sleep (CSWS) syndrome. Inhibitory seizures are usually considered as the underlying mechanism. However, published polygraphic recordings are rare. We report the case of a 22 month-old boy suffering from a
symptomatic CSWS syndrome associated with a perinatal stroke involving the
right middle cerebral artery territory. He presented with psychomotor regression
and daily multiple falls related to myoclonic-atonic seizures. Neurophysiological
examination showed secondary generalized myoclonus systematically correlated
with a bilateral spike spreading from the right central area. This confirms that positive myoclonus, in addition to negative myoclonus, may be responsible for epileptic falls in CSWS syndrome. [Published with video sequences]
Key words: epileptic falls, myoclonic-atonic seizures, continuous spike-waves
during slow sleep, video-EEG

90

however, polygraphic studies are
rare. We report the case of a 22
month-old boy presenting with symptomatic CSWS and daily multiple falls
related to myoclonic-atonic seizures
demonstrated by polygraphy.

Case report
The patient is a 22 month-old boy,
born at term, after an uneventful pregnancy and delivery, with healthy parents and an unremarkable family history. After a few months, the parents

Epileptic Disord Vol. 11, No. 1, March 2009

doi: 10.1684/epd.2009.0251

Correspondence:
P. Vrielynck
Service de neurologie,
Hôpital de Jolimont,
159 rue Ferrer,
7100 Haine-Saint-Paul,
Belgium
<vrielynckp@hotmail.com>

Epileptic falls are mainly observed in
Lennox-Gastaut syndrome and epilepsy with myoclonic astatic seizure.
They are also described in continuous
spike-waves during slow sleep
(CSWS) syndrome. CSWS is a well
characterized age-dependant electroclinical pattern associated with cognitive regression and variable seizure
types including epileptic falls. These
are found in up to 44.5% of cases
(Tassinari et al. 2005), and negative
myoclonus is usually considered the
cause (Galanopoulou et al. 2000,
Guerrini et al. 1998). Unfortunately

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Myoclonic-atonic seizures in CSWS

noticed a slight left motor asymmetry but no medical
work-up was performed at this time. Independent walk
was achieved at 18 months. At this time, he was able to
speak a few words. When he was 22 months old, he was
admitted to hospital because of unsteadiness, daily multiple (see video sequence 3) falls and language regression.
Clinical examination revealed left hemiparesia predominating in the upper limb and a global developmental delay
with autistic features. Cerebral MRI demonstrated a large
stroke lesion in the right middle cerebral artery territory
(figure 1).
Electrophysiological findings
A prolonged polygraphic examination was performed
over 24 hours before treatment introduction, including
video-EEG with 19 electrodes placed according to the
10-20 international system, and concomitant surface
EMG recording of deltoid muscle activity.
During wakefulness, abundant focal, high voltage, interictal diphasic spikes and spike waves were observed.
Amplitude mapping showed tangential dipoles consistent
with a right precentral generator, with a centrotemporal
negativity and a frontal positivity. These interictal epileptic abnormalities were strongly activated during slow
sleep, and then bilaterally spread from the right side to
the left frontal area (figure 2). “Spike and wave index”
(SWI), calculated in accordance with Galanopoulou
et al. (2000), reached 72%. Neither tonic seizures nor

rapid rhythm discharges were noted during sleep. Sleep
spindles were rarely present and were found lateralized
to the left side.
Fourteen massive myoclonic jerks were recorded, only
during wakefulness, mostly involving proximal muscles
in the upper limbs (see video sequence 2). Deltoid EMG
showed that they were either lateralized to the left or bilateral with asymmetry, occurring earlier on the left side
(figure 3). While standing or sitting, a brief electromyographic silent period followed the positive myoclonus,
associated with a sudden fall of the head and the whole
body (see video sequence 1). This silent period was
recorded on the deltoid EMG, and loss of tonus in the
axial cervical musculature is suspected on the video.
Duration of the myoclonic jerk measured between 110
and 180 ms, while the post myoclonic electromyographic
silent period varied from 140 to 220 ms.
Myoclonic jerks were systematically time-locked to a
bilateral high-voltage diphasic spike. Symptomatic
“pre-myoclonic” spikes tend to spread more than asymptomatic ones and have greater amplitude, of more than
300 μV (figure 4). The latency between the right centrotemporal spike and the controlateral homologous spike
was constant, from 25 to 30 ms.
Follow-up
Treatment with sodium valproate, 20 mg/kg, was followed
by a decrease in falls and EEG abnormalities. Levetiracetam,

Figure 1. Cerebral MRI showing a large sequellar lesion in the right middle cerebral artery territory, sparing the thalamus.

Epileptic Disord Vol. 11, No. 1, March 2009

91

P. Vrielynck, P. Defresne

FP2
F4
C4
P4
O2

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F8
T4
T6
FZ
CZ
PZ
FP1
F3
C3
P3
O1
F7
T3
T5
ECG

Figure 2. Sleep EEG before any treatment. Nearly continuous diffuse asymmetrical spike-waves, predominant on the right side (300 μV, 1 sec).

40 mg/kg, was later added. Seizures disappeared and the
EEG dramatically improved during sleep and wakefulness.
Only sporadic right centrotemporal and left frontal spikes
were noted during slow sleep. However, no improvement

in neurological development, language or autistic behaviour was noted to date, 8 months following treatment.

Discussion
C4
800 µv

L. DELTOID
1 000 µv

C3
800 µv

R. DELTOID
1 000 µv

1 second

Figure 3. Secondary generalized epileptic myoclonus, followed by
brief silent period. The onset of the myoclonus is time-locked to the
peak of the negative spike on the controlateral central electrode.
“Premyoclonic” spike and myoclonus are clearly asynchronous.

92

The clinical history and EEG features of our patient support a diagnosis of CSWS syndrome. However, strict criteria according to the ILAE proposal (Engel 2001) are not
fulfilled due to an asymmetric spike wave and a SWI
below 85%. Moreover, it is difficult to clearly establish a
cognitive deterioration, as classically described in this
epileptic condition, in such a young child. The parents
report the correct use of a few words between 12 and
20 months which disappeared thereafter. At the time of
the first meeting, no more language was noticed and the
boy presented autistic features.
Atypical benign partial epilepsy (ABPE) might also be considered on account of the similarity in electroclinical
characteristics. Some authors (Dalla Bernardina et al.
2005) emphasize the nosological overlap between these
entities in which a combination of genetic and lesional
factors may be implicated. Indeed, in these epileptic syndromes, the abnormal electrical activity occurs during
childhood and disappears during adolescence, testimony
to the involvement of maturation factors. On the other
hand, lesions involving the cortex or the thalamus are
found in 30 to 60% of CSWS cases (Galanopoulou et al.

Epileptic Disord Vol. 11, No. 1, March 2009

Myoclonic-atonic seizures in CSWS

FP2-F4
F4-C4
C4-P4
P4-O2
FP2-F8

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F8-T4
T4-T6
T6-O2
FZ-CZ
CZ-PZ
FP1-F3
F3-C3
C3-P3
P3-O1
FP1-F7
F7-T3
T3-T5
T5-O1
ECG
R. Deltoid
L. Deltoid

Figure 4. Awake EEG, no treatment. Three massive myoclonic jerks were recorded on deltoid EMG, correlating with the negative spike component of a bilateral spike and wave complex predominant on the right centrotemporal region (500 µV, 1 sec). The third spike-wave discharge is asymptomatic.

2000) and are also described, although more rarely, in
ABPE (Aicardi 2000). Congenital strokes, like that
reported in the present case, represent a part of these
reported neuroradiological abnormalities.
In these syndromes, several seizure types have been
described: focal motor, tonic-clonic, atypical absences,
and seizures with falls. Polygraphic studies analysing
falls in CSWS and related syndromes are sparse. They
consist mainly of drop attacks, attributed to negative
myoclonus correlated with epileptic discharges, either
the spike or the slow wave following the spike. Loss of
muscular tone may be bilateral (Guerrini et al. 1998) or
focal, involving a lower limb (Capovilla et al. 2000;
Fernandez-Torre et al. 2004). de Saint-Martin et al.
(2001) classified these brief inhibitory phenomena as
“spike and wave related symptoms”. Positive myoclonias were also published in a case report (de SaintMartin et al. 1999), although involving only the face,
without leading to a fall. Similar to the patient in the
present study, symptomatic “interictal” spikes were
characterized by greater amplitude than asymptomatic
discharges.
Unlike these previous reports however, falls in the present case were provoked by positive massive bilateral
myoclonic jerks and probably the subsequent brief atonia
in deltoids and axial muscles of the neck and the trunk.

Epileptic Disord Vol. 11, No. 1, March 2009

The falls are thus consistent with myoclonic-atonic seizures. Each myoclonus is induced by a bilateral asynchronous spike spreading from a right centrotemporal
focus, with latency compatible with secondary bilateral
synchrony. Deltoid EMG revealed that bilateral myoclonus was also asynchronous, with a constant leading side,
consistent with secondary generalized myoclonus
(Guerrini et al. 2005).
Falls related to myoclonic-atonic seizures have previously
been reported in ABPE. In particular, Deonna et al. (1986)
published a series of six children presenting myoclonicastatic seizures and idiopathic partial epilepsy.
However, this study and the two other ABPE main series
contained no polygraphic recordings (Aicardi and
Chevrie 1982, Hahn et al. 2001).
Atonia following myoclonus could be related to a postmyoclonic inhibition phenomenon, first described by
Gastaut (1961). An active motor cortex inhibition related
to the slow wave component of the epileptic discharge
could also occur, previously suggested as the pathophysiological mechanism of negative myoclonus in ABPE
(Parmeggiani et al. 2004).
In conclusion, this polygraphic study shows numerous
epileptic falls in a child with symptomatic CSWS syndrome, related to massive myoclonic jerks and
myoclonic-atonic seizures. The neurophysiological

93

P. Vrielynck, P. Defresne

dromes in infancy, childhood and adolescence.. London: John
Libbey, 2005: 203-25.

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Legends for video sequences
Video sequence 1. Myoclonic-atonic seizure while
the child is sitting and playing, leading to unbalance.
Polygraphic recording of this seizure is shown in
figure 4, second picture.
Video sequence 2. Positive massive myoclonic jerk
with left-side predominance, correlating with an asymmetrical bilateral spike and wave discharge.
Video sequence 3. Sudden fall associated with spike
and wave discharge, not analysed with polygraphy.
Consequently, the mechanism is unknown: negative or
positive myoclonus, or perhaps a mixed phenomenon.

pattern is consistent with secondary generalized cortical
myoclonus. This thereby confirms that positive myoclonus, as well as inhibitory seizures, may be responsible
for the epileptic falls in CSWS syndrome.

□

Acknowledgments.
We thank Dr Maria Paola Valenti and Prof. Edouard Hirsch for their
helpful comments on the manuscript.

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