The role of EEG in the diagnosis and classification of the epilepsy syndromes: a tool for clinical practice by the ILAE Neurophysiology Task Force ...
←
→
Page content transcription
If your browser does not render page correctly, please read the page content below
Seminar in Epileptology
Epileptic Disord 2017; 19 (4): 385-437
The role of EEG in the
diagnosis and classification
of the epilepsy syndromes:
a tool for clinical practice
by the ILAE Neurophysiology
Task Force (Part 2)*
Michalis Koutroumanidis 1 , Alexis Arzimanoglou 2,3 ,
Roberto Caraballo 4 , Sushma Goyal 5 , Anna Kaminska 6 ,
Pramote Laoprasert 7 , Hirokazu Oguni 8 , Guido Rubboli 9 ,
William Tatum 10 , Pierre Thomas 11 , Eugen Trinka 12 ,
Luca Vignatelli 13 , Solomon L. Moshé 14
1 St Thomas’ Hospital, London, UK
2 University Hospitals of Lyon (HCL), Department of Paediatric Clinical Epileptology,
Sleep Disorders and Functional Neurology, Member of the European Reference Centre
EpiCARE, Lyon, France
3 Epilepsy Unit, Department of Paediatric Neurology, San Juan de Deu Hospital, Member
of the European Reference Centre EpiCARE, Barcelona, Spain
4 Hospital J P Garrahan, Neurology, Capital Federal, Buenos Aires, Argentina
5 Evelina Hospital for Children, London, UK
6 APHP, Hopital Necker-Enfants Malades, Department of Clinical Neurophysiology, Paris,
France
7 Children’s Hospital, Neurology, Aurora, Colorado, 80045, USA
8 Tokyo Women’s Medical University, Department of Pediatrics, Shinjuku-ku, Tokyo,
Japan
9 Danish Epilepsy Centre, Department of Neurology, Dianalund, Denmark
10 Mayo Clinic, Neurology, Jacksonville, Florida, USA
11 Hopital Pasteur, Neurology, Hôpital Pasteur 24C, Nice, France
12 Paracelsus Medizinische Privatuniversitat, Salzburg, Austria
13 IRCCS Istituto delle Scienze Neurologiche di Bologna, Bologna, Italy
14 Albert Einstein College of Medicine, Neurology, Neuroscience, and Pediatrics, Bronx,
New York, USA
*This report was written by experts selected by the International League Against Epilepsy
doi:10.1684/epd.2017.0952
FIGURES ONLINE
(ILAE) and was approved for publication by the ILAE. Opinions expressed by the authors,
however, do not necessarily represent the policy or position of the ILAE.
Correspondence:
Michalis Koutroumanidis Part 1 was published in the September 2017 issue of Epileptic Disorders : Koutroumanidis
St Thomas’ Hospital, M, Arzimanoglou A, Caraballo R, et al. The role of EEG in the diagnosis and classification
London, UK of the epilepsy syndromes: a tool for clinical practice by the ILAE Neurophysiology Task
Force (Part 1). Epileptic Disord 2017; 19(3): 233-98.
Epileptic Disord, Vol. 19, No. 4, December 2017 385M. Koutroumanidis, et al.
ABSTRACT – The concept of epilepsy syndromes, introduced in 1989,
was defined as “clusters of signs and symptoms customarily occurring
together”. Definition of epilepsy syndromes based on electro-clinical fea-
tures facilitated clinical practice and, whenever possible, clinical research
in homogeneous groups of patients with epilepsies. Progress in the fields
of neuroimaging and genetics made it rapidly clear that, although crucial,
the electro-clinical description of epilepsy syndromes was not sufficient to
allow much needed development of targeted therapies and a better under-
standing of the underlying pathophysiological mechanisms of seizures.
The 2017 ILAE position paper on Classification of the Epilepsies recognized
that “as a critical tool for the practicing clinician, epilepsy classification must
be relevant and dynamic to changes in thinking”. The concept of “epilepsy
syndromes” evolved, incorporating issues related to aetiologies and comor-
bidities. A comprehensive update (and revision where necessary) of the EEG
diagnostic criteria in the light of the 2017 revised terminology and concepts
was deemed necessary. Part 2 covers the neonatal and paediatric syndromes
in accordance with the age of onset. [Published with educational EEG plates
at www.epilepticdisorders.com].
Key words: epilepsy syndromes, EEG and epilepsy diagnosis, EEG protocols,
EEG Telemetry, EEG Atlas
1. Introduction specific genetic syndromes (such as GGE/IGE, progres-
sive myoclonus epilepsy, or Dravet syndrome [DS]),
Part 2 of this work includes the main neonatal and but others, such as the commonly encountered focal
paediatric epilepsy syndromes, presented according spikes in association or not with focal slowing, are in
to age at onset (Scheffer et al., 2017). CAE (Childhood keeping with aetiologies as diverse as genetic, struc-
Absence Epilepsy) and Eyelid Myoclonia with or with- tural, or unknown (see also section 1.6 of Part 1). In the
out Absences have already been discussed in Part 1 latter case, the EEG may localize the focus, highlight
(Koutroumanidis et al., 2017a) amidst the genetic (idio- the high probability of a structural lesion, and guide
pathic) generalized epilepsies (GGE/IGE). brain imaging studies.
As in Part 1, the structure of each chapter includes: There is a dominant maturational element in the
– (i) a brief overview of the presented syndrome; clinical and EEG presentation of the structural focal
– (ii) a description of the symptoms and semiology of epilepsies during childhood (Nordli et al., 2001), which
each of the seizure types that are associated with the may render localization and even lateralization of
syndrome; the responsible lesion very difficult, particularly in
– (iii) an EEG section with the pertinent background, younger children. In children up to 2-3 years of age,
interictal and ictal characteristics in the awake state and for example, the repertoire of seizure manifestations
sleep; has been shown to be limited, with four seizure
– (iv) recording protocols developed according to the types (epileptic spasms, tonic, clonic, and hypermotor
evidence presented in the preceding EEG section to seizures) constituting up to 80% of the total ictal semi-
maximize diagnostic yield at two levels of complexity ologies (Hamer et al., 1999). In addition, the interictal
(see section 1.5 of Part 1); and ictal EEG findings in infants and young children are
– (v) levels of EEG diagnostic confidence in accordance frequently diffuse, even when the responsible struc-
with the strength of the EEG findings (see section 1.3 tural lesion is small (supplementary figures 1.01-1.03),
of Part 1). a phenomenon presumably related to age-dependent
The importance of adequate pertinent clinical infor- hyperexcitability. Such bilateral or diffuse/generalized
mation for the use of the appropriate recording epileptic discharges may not per se preclude epilepsy
protocol and the correct interpretation of the EEG find- surgery (Wyllie et al., 2007; Arzimanoglou et al., 2016)
ings and clinically useful final EEG report across all ages or, on the other hand, prompt unsuitably early inva-
cannot be overemphasized (figure 1.01 of Part 1). sive procedures. It is important to emphasize that
In contrast to the important role of the EEG in the in this period of life, regional interictal background
clinical diagnosis and the characterization of epilepsy abnormalities, such as polymorphic delta activity (PDA)
syndromes, its contribution for the diagnosis of the (supplementary figure 1.04), are much more important
underlying aetiology is overall moderate. Certain indicators of the epileptic focus and the associated
EEG patterns and combinations may strongly indicate underlying structural lesion (Noh et al., 2013). As in
386 Epileptic Disord, Vol. 19, No. 4, December 2017The role of EEG in the diagnosis and classification of the epilepsies
Abbreviations
ABFEC: atypical benign partial epilepsy of childhood IED: interictal epileptic discharges
BFIE: benign familial infantile epilepsy IPS: intermittent photic stimulation
BFNE: benign familial neonatal epilepsy IS: infantile spasms
BFNIE: benign familial neonatal-infantile epilepsy LKS: Landau-Kleffner syndrome
BFNIS: benign familial neonatal-infantile seizures LGS: Lennox-Gastaut syndrome
BIE: benign infantile epilepsy MAE: myoclonic-atonic epilepsy
BRE: benign rolandic epilepsy MAS: myoclonic absence seizures
CAE: childhood absence epilepsy MEI: myoclonic epilepsy in infancy
CSWS: continuous spike-and-wave during slow sleep MS: myoclonic seizure
CTS: centrotemporal spikes OE-G: occipital childhood epilepsy of Gastaut
DS: Dravet syndrome OLE: occipital lobe epilepy
ED: epileptic discharge OS: Ohtahara syndrome
EIMFS: epilepsy of infancy with migrating focal seizures PDA: polymorphic delta activity
ELMA: eyelid myoclonia with absences PKD: kinesigenic dyskinesia
EMA: epilepsy with myoclonic absences PPR: photoparoxysmal responses
EMAS: epilepsy with myoclonic-atonic seizures PS: Panayiotopoulos syndrome
EME: early myoclonic encephalopathy RMEI: reflex myoclonic epilepsy in infancy
ESES: electrical status epilepticus during sleep S-B: suppression burst
FOS: fixation-off sensitivity SES: status epilepticus during sleep
FS: febrile seizure SSW: slow spike-waves
GSPWD: generalized spike/polyspike-and-wave discharges SWI: spike-wave index
GSWD: generalized spike-and-wave discharges TA: typical absences
GTCS: generalised toni-clonic seizure TLE: temporal lobe epilepsy
HV: hyperventilation WS: West syndrome
ICCA: infantile convulsions and paroxysmal choreoathetosis
the adolescent and the adult patient, sleep recordings 2. NEONATAL SEIZURES AND
should be pursued because they can activate epileptic SYNDROMES
discharges, which acquire higher lateralizing and local-
izing value during rapid eye movement (REM) sleep
2.1 Overview of neonatal seizures and epilepsies
(Ochi et al., 2011).
Clinical-EEG presentation changes with brain matura- Neonatal seizures require rapid diagnosis, aetiological
tion such that by the age of 6-7 years and in adolescents, workup, and therapy, as delayed recognition of a treat-
seizure symptoms and semiology, as well as interic- able cause can have a significant impact on the child’s
tal and ictal EEG findings, become similar to those neurodeveloment. In conjunction with advances in
in adults, providing valuable information about the neuroimaging, metabolic, and genetic testing, electro-
topography of the primary neural network that gen- clinical characterization with video-EEG recording
erates focal seizures. allows more rapid determination of seizure aetiol-
Neonatal structural focal epilepsies are comprehen- ogy and implementation of targeted treatment (e.g. in
sively discussed in Section 2 of this paper, while EEG metabolic disorders with treatable conditions such as
changes in specific paediatric epilepsy syndromes that pyridoxine- and pyridoxal 5 -phosphate dependent
may also relate to structural brain lesions (such as epilepsy) (for review see Pearl, 2016).
West syndrome [WS] or Lennox Gastaut syndrome Major aetiologies of neonatal seizures are acute cere-
[LGS]) are fully covered in the relevant chapters bral injury including hypoxic-ischaemic encephalopa-
here. Structural epilepsies in adults (also applicable thy, intracranial haemorrhage and infarctions, central
to adolescents and older children) have already been nervous system infection, metabolic disturbances,
described in Part 1 under specific lobar syndromes. congenital structural brain lesions, and drug with-
A specific chapter on structural focal epilepsies in drawal (Kang and Kadam, 2015; Arzimanoglou and
infancy and early and late childhood across the vari- Duchowny, 2018). Epilepsies beginning in the neona-
ous aetiologies is not included in this paper, but will tal period represent, therefore, an uncommon but
be the topic of a later publication. Readers are referred not rare cause of neonatal seizures (Mizrahi and
to the relevant chapters of excellent textbooks (Bureau Kellaway, 1998; Co et al., 2007; Volpe, 2008; Sands and
et al., 2012; Arzimanoglou et al., 2016). McDonough, 2016).
Epileptic Disord, Vol. 19, No. 4, December 2017 387M. Koutroumanidis, et al.
Stereotyped focal seizures beginning in the neonatal essentially the same (Ohtahara and Yamatogi, 2003;
period in the absence of metabolic or infectious distur- Aicardi and Ohtahara, 2005). EME is typically asso-
bances may reveal an underlying structural anomaly, as ciated with metabolic disorders and a degree of
focal cortical dysplasia or cortical tubers in tuberous familial occurrence (i.e. pyridoxine-dependency, non-
sclerosis complex (TSC), or more diffuse anomalies ketotic hyperglycinaemia, methylmalonic academia,
associated with major congenital brain malforma- proprionic acidaemia, molybdenum co-factor defi-
tions, such as hemimegalencephaly or lissencephaly. ciency, sulphite oxidase deficiency, Menkes disease,
Advances in identification of genetic causes of cerebral and Zellweger syndrome), while in OS, congenital or
dysgenesis in recent years include somatic mutation acquired structural brain lesions are more frequent
associated with hemimegalencephaly, type IIb Focal (hemimegalencephaly, lissencephaly, polymicrogyria,
Cortical Dysplasia, and Tuberous Sclerosis Complex Aicardi syndrome, dentato-olivaro dysplasia, and dif-
resulting from mutations in various components of the fuse cerebral migration disorders) (Schlumberger et
mTOR pathway (D’Gama et al., 2015). al., 1992; Miller et al., 1998; Ohtahara and Yamatogi,
Beside the focal structural epilepsy with neonatal 2006; Arzimanoglou and Duchowny, 2018). Numerous
onset, three electroclinical syndromes with neona- mutations have been associated with OS, including
tal onset are recognized by the International League ARX, mitochondrial glutamate transporter, SLC25A22,
Against Epilepsy (ILAE). One of these, Benign Famil- STXBP1, and SCN2A (Weckhuysen and Korff, 2014).
ial Neonatal Epilepsy, is characterized by transient Evolution to WS or multifocal epilepsy occurs more
seizures and good neurodevelopmental outcome. The frequently in OS. Both syndromes, EME and OS, are
two other syndromes belong to the encephalopathies fairly similar in terms of age at onset, EEG aspect
with epilepsy, are associated with a burst suppression of suppression-burst, and overlapping seizure types,
EEG pattern, and their prognosis is in most patients and therefore their distinction is often difficult and
extremely poor with high mortality during the first sometimes impossible in the beginning of the disease
months of life and severe development impairment. (Schlumberger et al., 1992). Moreover, some children
present motor manifestations during the bursts of
In neonatal-onset epilepsies without metabolic or activity that may be impossible to classify.
structural alteration, at least three groups with
related functions were identified: ion channels (i.e.
KCNQ2), regulators of forebrain development (e.g. Seizures: symptoms and semiology
ARX), and regulators of synaptic function (e.g. STXBP1) In the two syndromes, seizures begin very soon after
(Weckhuysen and Korff, 2014). Epilepsy with Infantile birth, usually within the first month of life (Yamatogi
Migrating Focal Seizures (EIMFS) (with de novo gain- and Ohtahara, 2002).
of-function mutation of KCNT1 as the most common In OS, the most characteristic seizures are epilep-
cause) can present near the end of the neonatal period. tic spasms and tonic seizures, in clusters or isolated
In addition to anamnestic, clinical, and imaging data, (Ohtahara and Yamatogi, 2006). They can be lateralized,
ictal and interictal EEG can direct to a possible aeti- or generalized but asymmetric particularly in neonates
ology, which helps determine the degree of cerebral with lateralized structural lesions. Other seizure types
dysfunction and prognosis, but also in the evaluation such as focal motor seizures and hemiconvulsions
of treatment response. The neonatal EEG recording occur in about a third of patients (Yamatogi and
should be at least 60 minutes long (to include wake- Ohtahara, 2002).
fulness and sleep) with elementary polygraphy (ECG, In contrast, myoclonic seizures (MS) (axial, segmen-
respiration) and bilateral EMG if abnormal movements tary, or erratic) are typical in EME and rare in OS. In EME,
are suspected (Beal et al., 2017). the frequency of seizures is variable but can be almost
continuous. Erratic and segmentary myoclonus occur
2.2 Neonatal epileptic encephalopathies: early on, often within the first few days or month of
Early-Infantile Epileptic Encephalopathy with life (Guerrini and Aicardi, 2003). In erratic myoclonus,
suppression-burst pattern (Ohtahara syndrome) jerks appear to shift randomly from one area of the
and Early Myoclonic Encephalopathy (EME) body to another, mainly involving the face or extrem-
ities. Axial myoclonus is less common. Focal clonic or
Overview subtle seizures may follow myoclonus.
Early Myoclonic Encephalopathy (EME) and Ohtahara Not infrequently, however, complex ictal movements
syndrome (OS) are severe neonatal or early infan- that are usually stereotyped in the given child and asso-
tile epileptic/developmental encephalopathies. They ciated with EEG bursts of paroxysmal activity can be
share some types of seizure and also a pertinent difficult to classify as either spasms or myoclonias.
EEG feature, namely the suppression-burst (S-B) pat- Focal seizures occur more or less equally in both
tern. The strategy for diagnostic EEG recording is conditions and are very common. These may be
388 Epileptic Disord, Vol. 19, No. 4, December 2017The role of EEG in the diagnosis and classification of the epilepsies
motor with deviation of the eyes, tonic posturing, or transient evolution into hypsarrhythmia in middle to
hemiconvulsions. Subtle seizure with autonomic phe- late infancy (Ohtahara and Yamatogi, 2006).
nomena, such as flushing or apnoea, can also occur
(Yamatogi and Ohtahara, 2002; Beal et al., 2017). Ictal EEG
Epileptic spasms. EEG during tonic spasms princi-
EEG section pally shows desynchronization with or without evident
rapid activity (Yamatogi and Ohtahara, 2002). Using
Background
video-EEG with surface electromyographic recordings
In EME, EEG can be normal at the onset of the seizures,
from deltoid muscles, Fusco and co-workers found
and repetitive EEGs may be necessary for the diagno-
each burst to be associated with tonic contraction of
sis (Ozyurek et al., 2005). When the presentation is
variable duration (Fusco et al., 2001) (supplementary
complete, there is no spatial or temporal organization
figure 2.03A and B). The erratic myoclonus usually has
(background rhythms are not different between cere-
no EEG correlate, while limb/axial myoclonus is usu-
bral areas and do not cycle/change with time and state
ally associated with bursts of spikes and polyspikes
of vigilance), and there are no physiological features
within the bursts of the S-B pattern (supplementary
in either wakefulness or sleep. S-B is the prevailing
figure 2.04).
interictal pattern, however, clinical seizures conco-
Complex stereotyped movements that are difficult to
mitant with the bursts have been reported (Fusco
classify as either spasms or myoclonias are also asso-
et al., 2001).
ciated with bursts of activity (high-amplitude spikes,
polyspikes, waves, and sharp waves). There is no clear
Interictal abnormalities correlation between the duration of the burst and the
In EME and OS, the suppression-burst (S-B) pattern type of seizure (supplementary figure 2.05 and 2.06).
consists of bursts of high-voltage asynchronous delta Focal seizures are associated with focal discharges
or theta waves, mixed with spikes and polyspikes of spikes or sharp waves, clinically associated with
(from 150 up to 350 V) that last from 1 to tonic eye deviation, unilateral clonic contractions, or
6 seconds and alternate with inter-burst intervals subtle or subclinical phenomena (supplementary fig-
of low-voltage (M. Koutroumanidis, et al.
B. High diagnostic certainty (probable) of life (in neonates born at full-term) or at around
The EEG shows stable/invariant S-B pattern without 40 post-menstrual weeks in premature neonates; rare
seizures. This also applies to basic level recording cases with seizure onset after the first four weeks
given the specificity of S-B in the absence of other of life have also been described. Prenatal and peri-
conditions that can show a similar/reminiscent EEG natal history is unremarkable and there is family
picture (hypoxia, phenobarbital, fentanyl, etc.-see dif- history of neonatal seizures. Two autosomal domi-
ferential diagnosis below). nant epilepsy syndromes may present with neonatal
C. Low diagnostic certainty (possible) seizures: BFNE and benign familial neonatal-infantile
No S-B is registered on the EEG, which may have been epilepsy/seizures (BFNIE/BFNIS) (Zara et al., 2013).
recorded too early during the course of the disease.
Note. BFNE was the first proper genetic epilepsy
Repeat basic or advanced recordings once seizures are
described, hence some more information on its genet-
established to register the typical S-B pattern/seizures
ics was deemed appropriate. Genetic mutation in BFNE
and move diagnostic certainty to probable or confir-
is found in around 90% of cases, with the KCNQ2
matory level.
encoding the voltage dependent K+ channel subunit
being the most common gene; occasionally KCNQ3
Differential diagnosis and SCN2A mutation were found in BNFE families
– (1) A discontinuous EEG pattern that may have some (Grinton et al., 2015). KCNQ2 mutations have also
similarities to S-B can be seen in neonatal hypoxic been found in families, in which one or more fam-
ischaemic encephalopathy. However, in this condition, ily members had more severe outcome, including
the pattern is usually transient and can be reactive or a variable degree of intellectual disability, suggest-
unstable in character. ing that the clinical disease severity may be related
– (2) A pattern reminiscent of S-B may be secondary to to the extent of the mutation-induced functional K+
treatment for neonatal status epilepticus with medica- channel impairment. Recently, de novo KCNQ2 muta-
tion, such as midazolam infusion and sometimes with tions were found in patients with neonatal-onset
opioids such as sufentanyl and fentanyl. drug-resistant seizures, psychomotor retardation, and
important interictal abnormalities including “suppres-
Indications for repeating advanced video-EEG sion burst” and abnormal neuroradiological features,
recording level thus defining a so-called “KCNQ2 encephalopathy”
– (1) Failure to record seizures. and the variable phenotype of KCNQ2-related epilep-
– (2) Clinical suspicion of other types of seizure and/or sies (Weckhuysen et al., 2012; Kato et al., 2013).
epileptic syndrome (focal structural epilepsy).
Note. Repeat video-EEG basic level recording to mon- Seizures: symptoms and semiology
itor response to treatment for possible metabolic Seizures usually start with tonic posture, head or eye
causes. deviation or staring, apnoea, and other autonomic
features, and often progress to unilateral or bilateral
Atypical EEG/video-EEG features to be highlighted clonic movements. The postictal state is brief, interic-
tal examination is unremarkable and feeding is normal.
in the EEG report, which may cast doubts on (or
Biochemical examinations and cerebral imaging are
refute) the diagnosis of a neonatal epileptic normal (Hirsh et al., 1993; Ronen et al., 1993; Grinton et
encephalopathy al., 2015).
Low amplitude of bursts, rare or absent spikes, Seizure remission in BFNE occurs at around 4-6 months
and moderate flattening during the hypoactivity of age, irrespective of treatment. Development is usu-
period would suggest other causes of neonatal ally normal and febrile or afebrile seizures are widely
encephalopathy. known to occur later in life after a prolonged seizure-
Persistence of physiological background features dur- free period in approximately 15-25% of BFNE cases
ing wakefulness and sleep. (Grinton et al., 2015).
2.3 Benign familial neonatal epilepsy (BFNE) EEG section
Overview Background
Benign Familial Neonatal Epilepsy (BFNE), previously Normal or subnormal.
known as Benign Familial Neonatal Seizures, belongs
to a group of autosomal dominant benign epileptic Interictal abnormalities
syndromes with onset during the first year of life. Interictal recordings are normal or show minor
Seizures typically start on the second or third day epileptiform or non-epileptiform focal or multifocal
390 Epileptic Disord, Vol. 19, No. 4, December 2017The role of EEG in the diagnosis and classification of the epilepsies
abnormalities (Grinton et al., 2015). A pattern called (For both basic and advanced recording levels)
“theta pointu alternant” can rarely occur in children Recording of typical ictal and interictal patterns.
with BFNE. It is defined as a dominant theta activ- B) High diagnostic certainty (probable)
ity that is non-reactive, alternating or discontinuous, (For both basic and advanced recording levels)
may be intermixed with sharp waves, and frequently Normal background activity but no seizures recorded.
shows inter-hemispheric asynchrony. It is present dur- C) Low diagnostic certainty (possible)
ing active and quiet sleep, impeding precise definition (For both basic and advanced recording levels)
of maturational age. “Theta pointu alternant” can be Slightly abnormal background activity with few focal,
found in other conditions and therefore is not consid- mostly multifocal, spikes or sharp waves), or atypical
ered as specific for BFNE. seizures recorded
Ictal EEG Indications for repeating advanced level video-EEG
Focal seizures with initial tonic phase. When recorded
recording
on video-EEG, semiology is typical and stereotyped
– (1) Failure to record seizures.
with initial diffuse hypertonia (symmetric or asymmet-
– (2) Clinical suspicion of other types of seizures
ric), associated with apnoea/cyanosis and followed by
or of acute underlying pathologies, such as hypoxia-
clonic movements, unilateral or involving the whole
ischaemia, infectious processes, metabolic distur-
body, symmetric or not. The semiology may also
bances, or diseases or other epileptic syndromes
consist of “staring” with the arrest of activity being
(structural focal epilepsies).
associated with autonomic or oculo-facial features
without clonic movements. Pure clonic seizures are
rare. Generalized seizures have never been reported Atypical EEG/video-EEG features to be highlighted
in this syndrome. Seizures are brief and last for less in the EEG report, which may cast doubts on or
than two minutes and may be very frequent, with up eliminate a diagnosis of BFNE
to 30 seizures per day. – Abnormal background activity
On the EEG, seizures begin with diffuse bilateral, – Abundant focal or multifocal interictal abnormalities
eventually asymmetric, flattening of the background – Suppression-burst pattern
activity for 5-20 seconds (which corresponds to the – Focal seizures without typical features of BFNE
tonic and/or apnoeic phase), followed by focal or bilat- – Epileptic spasms
eral rhythmic, high-amplitude slow waves, and then by – Myoclonias
sharp waves over the frontal, temporal or central areas
(corresponding to vocalizations, chewing, or unilateral
or bilateral clonic movements). The preponderance of 2.4 Focal structural epilepsy of neonatal onset
the ictal EEG changes and associated motor manifes-
tations may vary between the left and right side, from Overview
one seizure to the next, in the same child (Ronen et Among neonatal epilepsy syndromes, focal struc-
al., 1993; Hirsch et al., 1993) (supplementary figure 2.10 tural epilepsies are rare and may overlap with OS,
and 2.11). as both can share similar electroclinical presen-
tation. Indeed, studies focusing on electroclinical
aspects of focal structural epilepsies with neonatal
Recording protocols
onset other than those on epileptic encephalopathies
Basic level
with suppression-burst (S-B; see relevant chap-
Attempt to record during wakefulness and sleep, if ter) are scarce. Among 38 infants with seizures
possible with polygraphy (ECG, respiration, and bilat- beginning within the first two months (mean: 0
eral deltoid EMG to record autonomic and other ictal months), not related to acute symptomatic causes
signs). Seizures are expected to occur within a few (anoxic-ischaemic encephalopathies, neonatal stroke,
hours, as they are very frequent at onset and before metabolic, or infectious), the main seizure types were
treatment, sometimes amounting to status epilepticus. focal (76%) and epileptic spasms (24%) (Akiyama
Advanced level et al., 2010); 34 of those (89%) had focal seizures
Perform long video-EEG recordings for up to 24 hours and epileptic spasms in combination, with the sec-
to recover seizures. Polygraphy, as described in the ond seizure type appearing after a median of three
basic level, is mandatory. months. Multiple correspondence analysis, performed
on electroclinical features, showed that the presence
Levels of EEG diagnosis or absence of S-B pattern and of an asymmetry in
A) Confirmatory of suspected BFNE in neonates with the EEG background were the most meaningful vari-
relevant family history ables to separate these very-early-onset epilepsies into
Epileptic Disord, Vol. 19, No. 4, December 2017 391M. Koutroumanidis, et al.
subgroups, thus confirming the relevance of the S-B consist of minimal motor manifestations, with or with-
pattern in the classification of neonatal-onset epilepsy out autonomic signs.
syndromes (Akiyama et al., 2010; Yamamoto et al., Autonomic. These seizures manifest with a variety of
2011). While the asymmetry in interictal EEG was often paroxysmal autonomic changes such as alterations in
associated with the presence of a structural brain breathing, heart rate or blood pressure, salivation,
abnormality, the S-B pattern was also associated with sweating, and colour changes. Autonomic manifesta-
cerebral lesions in around half of the patients, as tions are often encountered in association with seizure
previously reported for OS (see relevant section and discharges that originate from the temporal areas
Aicardi and Ohtahara [2005], Akiyama et al. [2010], and (Watanabe et al., 1982), and have also been described
Yamamoto et al. [2011]). in subtle seizures.
Typically, the presence of a focal lesion is suggested by
stereotyped focal seizures, electrographically arising EEG section
from the same region (but potentially multifocal in the
Background
case of tuberous sclerosis complex), or by asymmetries
The background is usually normal on the non-
in voltage or frequency of background activities (Beal
affected hemisphere, but shows variable alterations
et al., 2017), however, interictal EEG can also be normal.
on the affected side that range from mild to com-
Although EEG findings can sometimes be fairly
plete absence of physiological features and contain
characteristic (for instance periodic focal abnormal-
paroxysmal abnormalities, or hemi-suppression-burst
ities in focal cortical dysplasia or cortical tubers
(supplementary figure 2.12 and 2.13).
[Domańska-Pakieła et al., 2014; Kotulska et al., 2014]),
or high-voltage monomorphic theta or delta activity in
lissencephaly), precise diagnosis relies on neuroimag- Interictal abnormalities
ing. Typically, treatment relies on epilepsy surgery, but The interictal paroxysmal patterns depend on the
response to medical treatment may be good (Kröll- type and the extent of the lesion. Spikes, polyspikes
Seger et al., 2007). and sharp waves, but also slow delta waves, some-
times of pseudo periodic occurrence (supplementary
figure 2.14), and focal rapid rhythms may be found
Seizures: symptoms and semiology over the affected side. Abnormalities may also include
Ictal semiology relates to the topography of the epilep- hemi-suppression bursts concerning the whole hemi-
tic discharge. Seizures may be tonic or clonic, or sphere, in which case they are highly suggestive of
exhibit only subtle motor manifestations or autonomic focal cortical dysplasia or hemimegalencephaly (sup-
symptoms, or be sub-clinical, especially when aris- plementary figure 2.15A). Nevertheless, absence of EEG
ing from temporal regions (Volpe, 1989; Mizrahi and abnormalities does not exclude the diagnosis of struc-
Kellaway, 1987; Mizrahi and Kellaway, 1998; Beal et al., tural focal epilepsy.
2017).
Focal clonic. These seizures consist of rhythmic Ictal EEG
(usually one to three jerks per second), repetitive Focal seizures may or may not be associated with
movements of the face, proximal or distal limb, or axial epileptic spasms in the given patient. Focal seizures
muscles. always begin in the same side or area of the brain and
Focal tonic. Sustained posturing of a limb or later- show stereotyped electroclinical course that relates
alized axial flexion characterizes these seizures that to the topography of the lesion, however, those in
can also be accompanied by sustained conjugate eye neonates with tuberous sclerosis complex may be
deviation to one side. Like focal clonic seizures, tonic multifocal. Coexistent epileptic spasms are usually
seizures are usually associated with synchronized EEG asymmetric and may precede, follow a focal seizure, or
discharges. occur during its evolution (supplementary figure 2.15B
Myoclonic. These seizures manifest as sudden brief and C).
irregular, single or multiple contractions of muscles The ictal EEG depends on the seizure type with focal
or muscle groups in the face, the proximal and distal flattening in focal tonic seizures, rhythmic, periodic
parts of the limbs, or the trunk. or irregular spiking in clonic seizures (supplemen-
Epileptic spasms. Spasms manifest as sudden flexion, tary figure 2.15C and 2.16), and rhythmic or periodic
extension or mixed flexion and extension of limbs, very-low-amplitude slow-wave discharges in “subtle”
neck, and body, which can be bilateral symmetric or subclinical seizures (supplementary figure 2.17).
or asymmetric, or focal. A spasm is longer than a Focal myoclonic jerks, unilateral or predominating on
myoclonic jerk, but less sustained than a tonic seizure. one side, may be present in cortical malformations
Motor automatisms. Also called “subtle”, these that involve central areas (supplementary figure 2.18
seizures occur frequently in the new-born and and 2.19).
392 Epileptic Disord, Vol. 19, No. 4, December 2017The role of EEG in the diagnosis and classification of the epilepsies
Recording protocols beyond the age of two years. The term “infantile
Basic and advanced level recordings are exactly the spasms”, particularly when used synonymously to
same as for neonatal epileptic encephalopathies with “West syndrome” should be reserved to very young
suppression-burst (see relevant chapter). children. The recent ILAE classification included the
term “epileptic spasms” when this seizure type is
Levels of EEG diagnosis observed at other ages. Hypsarryhthmia can also be
Clinical suspicion of focal structural epilepsy in incidentally recorded in the absence of spasms.
untreated neonates after exclusion of the most fre- In the vast majority of cases, IS are associated
quent causes of acute symptomatic neonatal seizures, with structural brain abnormalities, including perina-
which are mostly focal (such as in stroke) or multifocal tal ischaemia/hypoxia, congenital or early acquired
(such as in neonatal hypoxic ischaemic encephalopa- infections, abnormalities of cortical development,
thy). neurocutaneous conditions, etc., while familial cases
A. Confirmatory of diagnosis are rare. Prognosis depends on aetiology and is better
(For both basic and advanced recording levels) in children without apparent structural cause. In nearly
Recording of typical ictal and interictal features. half of the patients, WS evolves into LGS or multifocal
epilepsies.
B. High diagnostic certainty (probable)
(For both basic and advanced recording levels)
Typical focal interictal abnormalities, but no seizures Seizures: symptoms and semiology
recorded. Proceed with, or repeat advanced level EEG Epileptic spasms (ES) are the defining seizure type,
to register seizures and move diagnostic certainty to although they are not exclusive for WS (see also sec-
level A. tion on neonatal epileptic encephalopathies). ES are
C. Low diagnostic certainty (possible) brief muscle contractions that predominate in prox-
(For both basic and advanced recording levels) imal and truncal muscles and cause sudden flexion
(also known as “salaam spasms”), extension, or mixed
Bilaterally abnormal background activity with focal,
movements. EEG-EMG polygraphy recordings have
multifocal or diffuse interictal epileptiform abnormali-
shown that a spasm reaches the maximum contrac-
ties, or non-stereotyped seizures with multifocal onset
tion more slowly compared to myoclonia, but faster
(see below).
compared to a tonic seizure (Vigevano et al., 2001). ES
may be isolated but most frequently occur in clusters.
Indications for repeating advanced level video-EEG The intensity and frequency of the sequential ES in
recording each cluster often increase gradually to a peak, and
– (1) Failure to record seizures. then progressively decrease until they stop. ES can
– (2) Clinical suspicion of other types of seizure or of be “subtle”, limited to only grimacing, eye deviation,
acute underlying pathologies (as cited above). and head nodding, or even be subclinical. ES may be
asymmetric, or asynchronous, associated with various
Atypical EEG/video-EEG features to be highlighted focal components that may involve the limbs, head, or
in the EEG report, which may cast doubts on a eyes, or show compartmental and vegetative features
diagnosis of focal structural epilepsy (Watanabe et al., 2001). ES may be preceded or followed
Multifocal interictal abnormalities and multifocal and by, or intermixed with, focal seizures (Gaily et al., 1995).
non-stereotyped seizures. Stereotyped focal seizures preceding epileptic spasms
suggest a focal lesion and polygraphic video recording
is required for detailed analysis.
3. INFANCY/EARLY CHILDHOOD Focal seizures. Occur mainly in infants with overt cere-
bral lesions and can be multifocal. A focal seizure may
3.1 Infantile Spasms (IS) and West Syndrome (WS) trigger a cluster of spasms, or occur independently of
them.
Overview
WS is a unique, age-dependent epilepsy that fre- EEG section
quently presents in the first year of life, most
commonly between the first three to nine months Background
of life. Traditionally, the triad of clusters of epileptic Continuously abnormal during wakefulness and sleep.
spasms, developmental regression, and hypsarrhyth-
mia on the EEG is termed as WS. It is now recognized Interictal abnormalities
that infantile spasms (IS) may not always be associ- Hypsarrhythmia, a term coined by Gibbs and Gibbs
ated with the prototypical hypsarrythmic EEG pattern in their atlas of electroencephalography in 1952,
and can also affect children later in life, though rarely describes a high-voltage (hypsos=height), completely
Epileptic Disord, Vol. 19, No. 4, December 2017 393M. Koutroumanidis, et al.
disorganized and chaotic (without any discernible – (ii) a low-amplitude brief fast discharge;
normal background rhythm=arrhythmia) EEG pattern – (iii) a short-lasting diffuse flattening of ongoing activ-
(supplementary figure 3.01), which is the characteristic ity (supplementary figure 3.08 and 3.09).
interictal presentation in WS. At onset, hypsarrhythmia The frequency of occurrence of these three pat-
may be present only during drowsiness and light sleep, terns and their terminology has varied according to
but it soon becomes abundant during wakefulness. different authors, but the first pattern may be the
Wakefulness. The main (typical) pattern of hypsar- most frequent (Fusco and Vigevano, 1993; Vigevano
rhythmia occurs during wakefulness: it consists of et al., 2001). A transient disappearance or reduction
random high-amplitude slow wave and spikes that vary of the hypsarrhythmic pattern is usually seen during
from moment to moment, both in duration and loca- a cluster of ES (supplementary figure 3.08). Symmet-
tion (supplementary figure 3.01). Occasionally, spike ric epileptic spasms (supplementary figure 3.10) may
discharges appear to be focal, or multifocal, but never be idiopathic or of structural origin. Infants with brain
as a rhythmically repetitive and highly organized pat- lesions may show an asymmetry of the ictal high-
tern. The abnormality is almost continuous, but early amplitude slow wave, reflecting the pathologically
during the clinical course, the age-dependent physio- more involved hemisphere. Focal or unilateral fast dis-
logical background may be intermittently preserved. charges immediately preceding the high-voltage slow
Most frequently, hypsarrhythmia may predominate wave are highly suggestive of focal cortical lesion.
over the posterior head regions, while anterior pre-
dominance is rare and only seen after the first Recording protocols
year of age. Basic level
Sleep. Hypsarrhythmia remains maximal in sleep Stage Time: any time of the day, but preferentially dur-
1, but becomes less continuous during sleep Stages 2 ing spontaneous sleep and after feeding (planning
and 3, and disappears during REM sleep. During Stages arrangements with parents are essential).
2 and 3, a tendency of the multifocal spike and sharp Activation: sleep is strongly recommended, and if
wave discharges to group results in a quasi-periodic achieved, further recording of at least 10 minutes after
appearance of the paroxysmal activity (supplemen- awakening is required, as ES occur very often in that
tary figure 3.02). Physiological graphoelements of sleep period.
(vertex sharp transients, spindles, and K-complexes) Polygraphy: bilateral deltoid EMG is desirable, even at
are usually absent. the expense of complete 10-20 EEG cover.
A number of different variants of hypsarrhythmia Advanced level
have been reported beyond its typical presen-
Time: anytime of the day, but lengthy recordings are
tation (Hrachovy and Frost, 2003). These include
recommended to include spontaneous sleep and a
hypsarrhythmia with increased inter-hemispheric syn-
period after feeding; if necessary induce sleep. Allow
chronization (examples in supplementary figure 3.02
the patient to reach Stage 2 for at least 10-15 minutes
and 3.03), asymmetric hypsarrhythmia (supplementary
and record for at least 30 minutes after awakening.
figure 3.04), hypsarrhythmia with episodes of voltage
Polygraphy: bilateral deltoid EMG is mandatory.
attenuation (supplementary figure 3.05), hypsarrhyth-
mia with a consistent focus of epileptic discharges
(supplementary figure 3.06) or focal slowing, and other Levels of EEG diagnosis
patterns. Clinical suspicion of IS/WS in untreated infants
An underlying structural origin can be suspected A. Confirmatory of IS/WS
when the EEG reveals atypical hypsarrhythmia: for Ictal recording of epileptic spasms with interictal EEG
instance, predominating focal spikes or spike-waves showing typical hypsarrhythmia or any of its variants.
or slow complexes may indicate a focal lesion, addi- Recording of hypsarrhythmia and history of ES in clus-
tional abnormal rhythms (i.e. diffuse high-voltage ters upon awakening are sufficient for diagnosis of WS
theta-alpha activity) may indicate lissencephaly or at level 1 (if video-EEG is not available or if epilep-
pachygyria, and persistent asymmetry or asynchrony tic spasms do not occur during the recording; asking
may indicate a focal lesion or agenesis of the corpus parents to bring along video recordings of the typical
callosum; asymmetric ictal patterns or interspersing spasms on portable phones will allow clinical confir-
focal seizures (supplementary figure 3.07A to 3.07B) mation; there is no need for SD recording level 2
may be of similar significance (see ictal EEG below). (however, see clinical indications below).
B. High diagnostic certainty
(Probable IS/WS, for both recording levels 1 and 2).
Ictal EEG No hypsarrhythmia or spasms recorded, but presence
Ictal discharges associated with ES include: of multifocal spike discharges during sleep record-
– (i) a diffuse high-amplitude triphasic slow wave; ing and history of epileptic spasms in clusters upon
394 Epileptic Disord, Vol. 19, No. 4, December 2017The role of EEG in the diagnosis and classification of the epilepsies
awakening: repeat recordings level 1 and 2 (if possible) seizure freedom remains an exception, while patients
to record epileptic spasms or hypsarrhythmia. remain cognitively impaired, often severely. Early mor-
C. Low diagnostic certainty tality, sometimes due to sudden unexpected death in
(Possible IS/WS, for both recording levels 1 and 2). epilepsy (SUDEP), occurs in about 10% of patients.
No hypsarrhythmia, but presence of multifocal spike DS is a channelopathy due to mutation in the
discharges during sleep recording and history of pos- SCN1A gene which encodes the alpha 1 subunit
sible (subtle) epileptic spasms (for instance, head of the voltage-gated sodium channel. SCN1A abnor-
nodding or eye deviation): Repeat recordings level 1 malities (mostly mutations and deletions) in DS are
and 2 (if possible) to record the ictal EEG of the attacks reported in 80% of patients. Identifying SCN1A muta-
and confirm the diagnosis of IS by showing that the tions might be helpful in some patients as a means
ictal EEG pattern is compatible with that of epileptic of supporting an early diagnosis of DS. However,
spasms. SCN1A aberrations can be associated with several
epilepsy syndromes, ranging from mild phenotypes
Indications for repeating advanced level SD found in families with genetic epilepsy with febrile
recording seizures plus (GEFS+) to the severe infant-onset DS.
Thus, diagnosis of DS is still based on the constel-
– (1) First EEG (recording level 1 or 2) normal or incon-
lation of the many different seizure types and their
clusive.
EEG characteristics, and their evolution, as described
– (2) Resistance to appropriate AED (vigabatrin,
by Dravet.
adrenocorticotropine, predonine).
Indications for video telemetry Seizures: symptoms and semiology
– (1) Clinical suspicion of additional seizure type. Seizures start in the first year of life in previously
– (2) Confirm the treatment response. healthy children. Initial seizures are unilateral or gen-
eralized convulsive, mainly clonic or tonic-clonic and
3.2 Dravet syndrome (DS) often prolonged (>10 min), evolving into status epilep-
ticus. They are typically triggered by fever (giving
Overview initially the impression of atypical febrile convulsions),
Dravet Syndrome is an infantile-onset epilepsy syn- or occur after immunization, but may also be afebrile.
drome, first described in 1978 by Charlotte Dravet Other types of seizure, mostly afebrile, occur in the
as “severe myoclonic epilepsy in infancy”. Estimated second or third year of life in addition to the convul-
prevalence is around 1% of epilepsy syndromes in sive seizures that are present throughout the evolution
infancy and childhood with males being more often (Bureau and Dalla Bernardina, 2011; Dravet et al., 2012).
affected. The natural course of DS during childhood Myoclonic seizures may be absent at the first stages of
is traditionally divided into an early phase (roughly the syndrome (Guerrini and Aicardi, 2003).
corresponding to the first year of life) and a steady A. Convulsive seizures are traditionally classified into:
phase within the next 2-5 years, during which the – (i) “Unilateral” with clear hemi-clonic or tonic
full electroclinical picture becomes established. In convulsions that, on different occasions, may alter-
the early phase, prolonged hemi- or generalized nate sides in the same child; such alternating unilateral
convulsive seizures occur, typically associated with seizures can offer a significant clue to early diagnosis
fever, while some children show generalized pho- of DS. These seizures become rarer with age.
toparoxysmal responses (PPR) to photic stimulation, – (ii) “Generalized tonic-clonic” seizures as in
an unusual finding for this age. During the steady IGE/GGE, although of somewhat shorter duration.
phase, MS, atypical absences, complex partial seizures – (iii) “Falsely generalized” and “unstable” seizures.
(CPS), and episodes of non-convulsive status may also These are bilateral convulsive but with asymmetric
appear, while cognitive development slows leading clonic or tonic movements and postures, at times pre-
to moderate/severe intellectual disability usually after dominating on one side, or switching sides during the
the age of 4-5 years; some children may also show seizure. For falsely generalized seizures, the descrip-
non-progressive ataxia, pyramidal signs, or hypoto- tion reported by the family appears to correspond to
nia. Seizure evolution may vary in some children; for a generalized tonic-clonic seizure (GTCS), but poly-
instance, clear association with fever may be lacking graphic video-EEG recordings have shown that the
and myoclonic or CPS may start early. Such course onset of the bilateral motor manifestations may lag
variability and the overall seizure polymorphism, as behind a brief period of eye opening and unrespon-
well as the largely non-specific interictal EEG findings, siveness, associated or not with eye deviation and facial
may delay diagnosis. Long-term outcome is invari- jerking. The EEG onset is bilateral synchronous but
ably unfavourable. DS is highly pharmaco-resistant and often asymmetric in the falsely generalized seizure
Epileptic Disord, Vol. 19, No. 4, December 2017 395M. Koutroumanidis, et al.
and focal in the unstable seizure (see EEG section). Sleep. Normal patterns, at least initially.
Both these types tend to mainly occur during non-REM After the first year, there is usually a gradual slowing
sleep. of the background activity, more marked if seizures
B. Focal seizures, usually of the complex partial are frequent. Theta band waves predominate over the
type, are frequently associated with autonomic symp- central areas with persistence of physiological patterns
tomatology (pallor, cyanosis, respiratory changes, and (supplementary figure 3.12). Physiological sleep phe-
drooling), oral automatisms and hypotonia, and some- nomena and organization generally remain preserved,
times with eyelid or distal jerks. They last from one unless frequent nocturnal seizures occur.
to a few minutes; when longer they can evolve into a
unilateral motor or secondary generalized seizure. Interictal abnormalities
C. Myoclonic seizures can be either massive axial Interictal abnormalities may be present at onset
movements leading to falls or mild (isolated or (22% of patients) and increase during evolution
grouped) manifesting as a few jerks. Erratic myoclonias (77%) (Specchio et al., 2012). Generalized, focal and
may also occur. multifocal abnormalities, spikes, and spike-wave or
D. Atypical absences may be at times associated with polyspike-wave discharges, symmetric or not, are more
a myoclonic component. frequent over the frontal and central areas, but also
E. Non-convulsive status epilepticus (NCSE), also occur over the temporal and occipital areas (supple-
known as obtuntation status: NCSE episodes consist mentary figure 3.13).
of prolonged (hours or days) impairment of con- Interictal abnormalities are usually enhanced during
sciousness with loss of contact or variably reduced sleep (supplementary figure 3.14). Generalized PPR
responsiveness, hypotonia and somnolence, and occur in 9% of patients at onset, increasing to 22-
erratic or segmental myoclonus. Obtundation status 44% during evolution (Specchio et al., 2012; Caraballo
may be initiated, punctuated or terminated by gener- and Fejerman, 2006). Slow waves occur mainly over
alized tonic-clonic seizures, or be combined with other the central regions at onset and tend to diffuse dur-
seizure types, such as axial myoclonic, myoclonic- ing evolution. Both generalized and focal spikes and
atonic or clonic. spike-wave discharges and slow waves are enhanced if
F. Tonic seizures are exceptional. seizures are more numerous.
Seizures may be triggered by intermittent photic stim- There is no homogeneous evolution of the EEG aspects
ulation (IPS), visual patterns, hot water immersion, and with age, with the overall pattern in the individual
physical effort (Dravet et al., 2012), and sensitivity to patient being dependent on the number and dura-
photic or pattern stimulation is noted in approximately tion of seizures. A distinctive EEG pattern of frontal
40% of patients, particularly in younger children. slow bi- or triphasic spikes, followed or not by slow
Status epilepticus or at least worsening of seizures may waves when awake and activated by sleep with dif-
be provoked by inappropriate AEDs (carbamazepine, fuse 5-10-second discharges of 8-9-Hz polyspikes, has
lamotrigine, and vigabatrin). In adults, MS, atypical been noted in a minority of adolescents with DS,
absences, and focal seizures tend to remit, but long- some of whom had tonic seizures (Nabbout et al.,
lasting clonic seizures or short tonic-clonic seizures 2008); despite some similarities with LGS, this pattern
may persist, particularly during sleep (Ohki et al., 1997). does not indicate transition of DS to LGS (see also
section on LGS).
EEG section
Although abnormalities are non-specific, interictal Ictal EEG
EEG is helpful for differential diagnosis and patient A. Convulsive seizures
management. Moreover, sequential EEG recordings – (i) Unilateral. These are frequent at the onset of
may demonstrate the evolution of DS, while ictal the disease. The ictal discharge is characterized by
recordings with EMG polygraphy document seizure rhythmic (2-3/second) bilateral slow waves of higher
polymorphism, which is diagnostically very important. amplitude over the hemisphere contralateral to the
clinical manifestations and intermixed with 10/second
Background recruiting rhythms.
Wakefulness. Background activity is normal at onset In other focal unilateral seizures, the EEG pattern can
despite the frequent seizures; rhythmic theta activities be variable with onset over the frontal or frontal-
of 4-5 Hz may be present over the central-parietal areas central regions of one hemisphere, or with bilateral
and vertex. Diffuse or asymmetric slowing may be seen asymmetric onset, but always predominant over the
if EEG is performed immediately after a seizure; some- frontal areas (supplementary figure 3.15A, B). The EEG
times, focal postictal abnormalities may linger on for a onset consists of “pseudo-rhythmic” spikes and waves,
few days (supplementary figure 3.11). contralateral to the clinical manifestations, and may be
396 Epileptic Disord, Vol. 19, No. 4, December 2017The role of EEG in the diagnosis and classification of the epilepsies
periodically interrupted by a 1-2-second flattening of Recording protocols
the EEG. Basic level
– (ii) Generalized tonic-clonic seizures (See section on Planned recording during wakefulness and sleep with
IGE/GGE). polygraphy (ECG, respiration, bilateral deltoid EMG)
– (iii) “Falsely generalized” and “unstable” seizures. with hyperventilation (HV) and IPS. IPS is important to
In the falsely generalized seizures, the EEG discharge record early photoparoxysmal responses.
is of bilateral symmetric or asymmetric onset with a Advanced level
slow spike or SW, sometimes followed by a brief atten- Long-duration video-EEG with polygraphy, as above
uation, and fast activities intermixed with slow waves. (with at least bilateral deltoid EMG). Include IPS and
These seizures can be preceded by isolated massive HV, as in level 1. Hospitalization of the child during a
jerks for several minutes, increasing progressively in cluster of febrile or afebrile seizures provides a good
frequency and amplitude. opportunity.
Unstable seizures are characterized by varying topo- Sleep is important to enhance the probability of
graphic changes of the ictal discharge. The seizure can recording interictal discharges and unstable and
start over one area of one hemisphere and then spread falsely generalized seizures. More extensive EMG
to another area of the same hemisphere or to the entire polygraphy will better demonstrate the ictal polymor-
hemisphere, or asymmetrically to both hemispheres. phism of these seizure types.
The pattern of propagation is variable from one seizure Repeat sleep EEGs when clinically indicated (i.e.
to another in the same patient. appearance of a new seizure type) to better document
In general, polygraphic video-EEG recordings of both the evolution of the syndrome.
these seizure types have documented complex ictal
evolution and a degree of discrepancy between
Levels of EEG diagnosis
clinical and EEG manifestations (for further details
As already discussed, diagnosis of DS relies on the
see Bureau and Dalla Bernardina [2011] and Dravet
clinical evolution and is supported by serial (and as
et al., 2012).
frequent as possible) video-EEG evidence that will
B. Focal (complex partial) seizures
document seizure polymorphism. Early EEG photo-
Ictal EEG consists of a rhythmic sequence of fast
sensitivity and video-recorded falsely generalized or
polyspikes intermixed with theta activity during the
unstable seizures provide pertinent diagnostic clues. It
last part of the seizure, involving, for the duration
follows that confirmatory (level A) and probable (level
of the seizure, the temporal-parietal-occipital region
B) levels are not applicable here, as for most of the
of one hemisphere or more rarely a frontal region
other syndromes; in DS, there are no specific interictal
(Bureau and Dalla Bernardina, 2011) (supplementary
features, and seizure polymorphism is unlikely to be
figure 3.16).
shown by even an ictal EEG.
C. Myoclonic seizures
In the untreated child with suspected DS, the first
These are accompanied by generalized spike- or EEG (both basic and advanced recording levels) can
polyspike-wave discharges at 3Hz or more, lasting 1-3 increase diagnostic certainty if it shows a combination
seconds and of higher voltage over the central-parietal of the following:
areas (supplementary figure 3.17 and 3.18).
– (1) Background showing focal or diffuse slowing
D. Atypical absences in postictal recordings, following repeated admissions
These are associated with generalized regular or irreg- for atypical febrile seizures (FS) or status epilepticus.
ular spike-wave discharges at 2-3.5 Hz, lasting 3-10 – (2) Early-onset photosensitivity.
seconds, and are accompanied by impaired con-
– (3) Myoclonic and either unstable or falsely general-
sciousness and sometimes a myoclonic component
ized seizures.
(supplementary figure 3.19).
C) Low diagnostic certainty (possible)
E. NCSE (obtuntation status)
(For both basic and advanced recording levels)
EEG background activity is replaced by diffuse delta
Monomorphic epilepsy syndrome with only
slow waves, superimposed with multifocal spikes
myoclonus.
and spike-waves, sharp waves, and generalised spike-
Development remains unaffected.
and-wave discharges (GSWD) predominating over
frontal-central areas, associated with myoclonic jerks
or without a clinical correlate (atypical absence status). Indications for video-EEG telemetry
F. Tonic seizures – (1) Worsening with suspicion of minor status epilep-
These occur only exceptionally and are associated with ticus.
diffuse discharges of polyspikes at 8-9 Hz (Nabbout et – (2) Clinical suspicion of other types of seizures
al., 2008). and/or epilepsy syndrome.
Epileptic Disord, Vol. 19, No. 4, December 2017 397You can also read
