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Epileptic Disord, Vol. 19, No. 3, September 2017 233

FIGURES ONLINE

Correspondence:Michalis KoutroumanidisGSTT, Clin Neurophysiology andEpilepsiesSt Thomas’ Hospital, London, UK

Seminar in EpileptologyEpileptic Disord 2017; 19 (3): 233-98

The role of EEG in thediagnosis and classificationof the epilepsy syndromes:a tool for clinical practiceby the ILAE NeurophysiologyTask Force (Part 1)*

Michalis Koutroumanidis 1, Alexis Arzimanoglou 2,Roberto Caraballo 3, Sushma Goyal 4, Anna Kaminska 5,Pramote Laoprasert 6, Hirokazu Oguni 7, Guido Rubboli 8,William Tatum 9, Pierre Thomas 10, Eugen Trinka 11,Luca Vignatelli 12, Solomon L Moshé 131 GSTT, Clin Neurophysiology and Epilepsies, St Thomas’ Hospital, London, UK2 University Hospitals of Lyon, Department of Clinical Epileptology, Sleep Disorders andFunctional Neurology in Children, Lyon, France3 Hospital J P Garrahan, Neurology, Capital Federal, Buenos Aires, Argentina4 Evelina Hospital for children GSTT, Clinical Neurophysiology, London, UK5 APHP, Hopital Necker-Enfants Malades, Department of Clinical Neurophysiology, Paris,France6 Children’s Hospital, Neurology, Aurora, Colorado, 80045, USA7 Tokyo Women’s Medical University, Department of Pediatrics, Shinjuku-ku, Tokyo,Japan8 Danish Epilepsy Centre, Department of Neurology, Dianalund, Denmark9 Mayo Clinic, Neurology, Jacksonville, Florida, USA10 Hopital Pasteur, Neurology, Hôpital Pasteur 24C, Nice, France11 Paracelsus Medizinische Privatuniversitat, Salzburg, Austria12 IRCCS Istituto delle Scienze Neurologiche di Bologna, Bologna, Italy13 Albert Einstein College of Medicine, Neurology, Neuroscience, and Pediatrics, Bronx,New York, USA

ABSTRACT – Rational. The concept of epilepsy syndromes, introduced in1989, was defined as “clusters of signs and symptoms customarily occurringtogether”. Definition of epilepsy syndromes based on electro-clinical fea-tures facilitated clinical practice and, whenever possible, clinical researchin homogeneous groups of patients with epilepsies. Progress in the fieldsof neuroimaging and genetics made it rapidly clear that, although crucial,

∗This report was written by experts selected by the International League Against Epilepsy(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.

mailto:[email protected]


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M. Koutroumanidis, et al.

the electro-clinical description of epilepsy syndromes was not sufficient toallow much needed development of targeted therapies and a better under-standing of the underlying pathophysiological mechanisms of seizures. The2017 ILAE position paper on Classification of the Epilepsies recognized that“as a critical tool for the practicing clinician, epilepsy classification mustbe relevant and dynamic to changes in thinking”. The concept of “epilepsysyndromes” evolved, incorporating issues related to aetiologies and comor-bidities. A comprehensive update (and revision where necessary) of the EEGdiagnostic criteria in the light of the 2017 revised terminology and conceptswas deemed necessary.Methods. The work was commissioned by the Neurophysiology Task Forceof the ILAE Committee on the Diagnostic Methods. Diagnostic criteriaand recording procedures were developed by group consensus, reachedthrough an “informal”, internal decision-making process. Each workinggroup member was allocated a number of syndromes, and a standard struc-tured template was used. International literature was extensively reviewed.Results. We developed a simple diagnostic system that is applicable to allepilepsy syndromes which allows the physician (i) to rate the strength ofEEG diagnosis (degree of diagnostic certainty) by weighting EEG findings inrelation to the available clinical information or the specific clinical question,and ii) to suggest further EEG diagnostics where conclusive diagnostic evi-dence is lacking. We also propose a system of syndrome-specific recordingprotocols that, used with the relevant clinical presentation or specific clini-cal question, may maximize activation of epileptic discharges and ultimatelyhelp with standardization of EEG recording across departments, worldwide.Because recording methodology also depends on available resources, atwo-tier system was developed to embrace clinical EEG services in resource-limited and industrialized countries. A clinical practice statement for each ofthe epilepsy syndromes discussed underscores the crucial role of the clini-cal information with regards to both the optimization of the EEG recordingand mainly its meaningful interpretation. Part I covers Genetic (Idiopathic)generalized epilepsies and syndromes, Reflex epilepsies, structural and

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. Introduction

he EEG is the most dependable “laboratory” inves-igation for epilepsy as it allows us to study its

ost relevant functional markers: the interictal andctal epileptic discharges (ED). Furthermore, as cer-ain clusters of abnormal graphoelements are stronglyssociated with (and sometimes specific to) distinctlinical epilepsy phenotypes, the EEG has been a deci-ive tool for the classification of seizures and epilepsiesGastaut, 1970; Commission, 1981, 1985, 1989).

ur understanding of the epilepsies has progressed

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hrough clinical-EEG, imaging, genetic, and moleculariology research, and further approaches to classifi-ation have been attempted (Engel et al., 2001; Engel,006), culminating with the latest ILAE position papern revised terminology and concepts of seizures andpilepsies (Scheffer et al., 2017). Despite substantialdvances, the clinical and electroencephalographic

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syndromes and Progressive Myoclonus Epilepsiesational EEG plates on www.epilepticdisorders.com].

yndromes, EEG and epilepsy diagnosis, EEG protocols

lassification of epileptic seizures of 1981 marked theast official attempt of the ILAE to define EEG crite-ia, which are duly in keeping with the dichotomouspproach of the 1981/1989 ILAE classification frame-ork (Commission, 1981, 1985, 1989). A comprehensivepdate (and revision where necessary) of the EEG dia-nostic criteria in the light of the revised terminologynd concepts was deemed necessary and the workas commissioned by the Neurophysiology Task Forcef the ILAE Committee on the Diagnostic Methods.

Epileptic Disord, Vol. 19, No. 3, September 2017

working group of EEG/clinical epileptology expertsas formed to comprehensively cover the main pae-iatric and adult syndromes and epilepsies; Chairnd Memberships were agreed after consultation withhe ILAE Executive Committee (Liaison Prof Wiebe)nd the ILAE Classification Committee (Liaison Profirsch).

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The role of EEG in the diagnosis and classification of the epilepsies

AbbreviationsADNFLE: autosomal dominant frontal lobe epilepsy JAE: juvenile absence epilepsyADPEAF: autosomal dominant partial epilepsy with JME: juvenile myoclonic epilepsyauditory features LEV: levetiracetamAED: antiepileptic drug LTG: lamotrigineAM: action myoclonus MELAS: mitochondrial encephalomyopathy, lactic acidosisASE: absence status epilepsy MS: myoclonic seizuresBZD: benzodiazepines mTLE: mesial temporal lobe epilepsyCAE: childhood absence epilepsy MTS: mesial temporal sclerosisCAP: cyclical alternating pattern NREM: non-rapid eye movementCBM: carbamazepine nTLE: neo-cortical (lateral) temporal lobe epilepsyCLZ: clonazepam OIRDA: occipital intermittent rhythmic delta activityDnASLO: de novo absence status of late onset OLE: occipital lobe epilepsyED: epileptic discharges OPM: orbitofrontal photo myoclonusELMA: eyelid myoclonia with absences PNES: psychogenic non-epileptic seizureE-PA: epilepsy with phantom absences PPR: photoparoxysmal responseESX: ethosuximide RBD: REM behavioural disorderfmTLE: familial mesial temporal lobe epilepsy REM: rapid eye movementFOS: fixation-off sensitivity SBS: secondary bilateral synchronyFS: febrile seizures SD: sleep deprivationGCTC: generalized clonic-tonic-clonic seizures SDEEG: EEG after partial sleep deprivationGGE: genetic generalized epilepsy sec-GTC: secondary generalized tonic-clonicGPSWD: GSWD with a polyspike component SI: self-inductionGSWD: generalized spike-wave discharge SOZ: seizure onset zoneGTCS: generalized tonic-clonic seizures SSEPs: somatosensory evoked potentialsGTCSa: generalized tonic-clonic seizures alone TA: typical absences

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.1 Aims

his report intends to propose:(1) A simple diagnostic system that is applicable to

ll epilepsy syndromes and could enable electroen-ephalographers:• i) to rate the strength of EEG diagnosis (degree ofdiagnostic certainty) by weighting EEG findings inrelation to the available clinical information or thespecific clinical question;• ii) to suggest further EEG diagnostics whereconclusive diagnostic evidence is lacking.

t is anticipated that an effective and easy-to-use dia-nostic rating system could also improve homogeneity

n EEG interpretation and reporting.he default rating system is organized at three levels of

pileptic Disord, Vol. 19, No. 3, September 2017

iagnostic certainty and explained below (section 1.3).he principles of the diagnostic EEG from the planningf the recording to its interpretation and reporting arettingly discussed below in section 1.4.(2) A system of syndrome-specific recording pro-

ocols that, used in the relevant clinical presentationr the specific clinical question, may maximize

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ctivation of ED and ultimately help with standardiza-ion of EEG recording across departments, worldwide.ecause recording methodology also depends onvailable resources, a two-tier system was developedo embrace clinical EEG services in the resource-imited and the industrialized countries; the system isescribed in section 1.5.he transition from the 1989 to the 2010-2017 termi-ology and concepts did not encounter significantifficulties because both clinical taxonomies are basedn epilepsy syndromes. Particular concepts and terms

hat connote aetiology but are not directly adaptableo the 2010 proposal, such as that of “idiopathy”, areiscussed in section 1.6.

t is very much hoped that this work becomes a usefulducational tool for all EEG technologists and physi-ians who see people with epilepsy, report EEGs, or

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oth, particularly outside tertiary epilepsy centres.

.2 Methodology

iagnostic criteria and recording procedures wereeveloped by group consensus, reached through

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informal”, internal decision-making process (Fink etl., 1984; Qaseem et al., 2012). Each working groupember was allocated a number of syndromes, andstandard structured template was used.formal systematic search was not performed. How-

ver, the literature was extensively reviewed (noestrictions regarding language or type of publica-ion) and, to adhere to the practical and far-reachingducational character of this work, bibliography forach chapter is limited to a few most important recentnd best accessible references and also to seminalapers describing the pertinent EEG characteristicsf the syndromes, irrespective of their publicationate. Widely accepted glossaries and guidelines, andorking group consensus statements were taken into

ccount (Chatrian et al., 1974; Noachtar et al., 1999;lume et al., 2001; Flink et al., 2002), and EEG vocabularyas the same used by SCORE, the ILAE-endorsed com-uterized EEG reporting system (Beniczky et al., 2013);hen deemed useful, additional adequately explained

erms were used according to authors’ individualreferences.

nitial drafts of the chapters covering individual syn-romes were discussed between smaller “paediatric”nd “adult” groups and the chairperson. Interpreta-ion of evidence, development of diagnostic certaintyating (including further diagnostics when evidences lacking), and statements on recording protocolsvolved for each syndrome through a series of iter-tions and critiques with any differences resolved byonsensus.he working group plans periodic revision and updatef diagnostic criteria depending on new evidence andolleagues’ feedback.

.3 Layout of the chapters-syndromes

standard format was uniformly used, consisting ofhe following sections:

(1) Overview: contains a short description of the syn-rome or the epilepsy type, including its nosologicalo-ordinates.(2) Seizures: symptoms and semiology: provides a

rief description of all associated seizure types andheir important characteristics, including their relationo state of vigilance and other modulators and possibleriggers. The section contains essential information forlectroencephalographers to direct and interpret EEGecordings and for EEG technologists to collect impor-ant clinical data and to further develop their recording

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trategies (figure 1.01).(3) EEG section: contains pertinent information

bout background rhythms and the typical interictalnd ictal paroxysmal findings in wakefulness and sleep,ncluding the effects of possible activators and triggers.t also provides the rationale behind the proposed

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ecording protocols that follow. In some syndromes, aubsection of atypical findings contains EEG patternshat may be compatible with the class, in which theyndrome in question belongs, but are not suggestivef the particular syndrome.(4) Recording protocols: summarize the methodol-

gy and techniques that are more likely to activateD and other EEG characteristics of the particular syn-rome or epilepsy type to maximize diagnostic yield.his section aims to set up minimum recording stan-ards and homogenize diagnostic EEG methodologycross EEG departments, and to propose further dia-nostic techniques and strategies depending on thevailable resources.

(5) Levels of EEG diagnosis: the section essen-ially rates diagnostic confidence, assuming newlyresented patients and available essential clinical

nformation through sound medical referrals, data col-ection by the EEG technologist, or both. Becauseowadays brain imaging may be available at the timef the recording, relevant information may be taken

nto account, particularly when focal syndromes andpilepsies are concerned.ollowing successive rounds of internal deliberationsnd critiques, and a number of trials, diagnosticonfidence for a particular working clinical hypoth-sis/question was simply, clearly and convenientlyraded, from highest to lowest, into the following

evels:A) Confirmatory of clinical diagnosis. The EEG con-

ains: i) typical seizure(s); ii) typical interictal epilepticctivity; iii) no atypical features.B) High diagnostic certainty (probable). No seizure

s recorded, but the EEG contains: i) typical interictalpileptic activity; ii) no atypical features.ote: In many syndromes levels A and B are essen-

ially of similar diagnostic value. With the exceptionf mainly paediatric syndromes and epilepsies, whichften manifest with frequent seizures or clusters ofeizures (such as epileptic spasms), syndromes withypical absences (TA), and reflex epilepsies, a seizure iseither expected nor pursued during a waking or sleepEG recording (for instance, in a patient with a work-ng hypothesis of temporal lobe epilepsy and monthlyeizures). In such cases, both levels A (when a temporalobe seizure is recorded by chance) and B (unilateralemporal spikes) are sufficiently diagnostic.

C) Lower diagnostic certainty (possible). When noeizure is recorded, but the EEG contains: i) typicalnterictal epileptic activity and ii) some atypical fea-


ures. In this scenario, findings are diagnostic of theype (class) of epilepsy (for instance, genetic [idio-athic] generalized or structural focal), but not strictlyuggestive of the particular syndrome in question.t this level of confidence, other possibilities within

he given class of epilepsy remain open and further

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Referring physician

EEG request

Specific tasksandrequirements

PrincipalEEGobjectives

Diagnostic hypothesisor clinical question(s)

Pertinent clinicalInformation

EEG recording

Additional clinicalinformation

Analysis & synthesis ofresults, including conditionsof recording, backgroundrhythms, ED and theirbehavior in different statesof vigilance and activations

Formation of a diagnostichypothesis that “fits ” theclinical presentation

Collection of pastEEG recordings

Factual report

Individualizationof the recording- Sleep, Polygraphy, Activation etc.

EEG technologist Electroencephalographer

EEG reporting

Normal or abnormalresults

Clinical correlations ofthe findings / EEGdiagnosis

In case of uncertainty1. Explain rationale2. Indicate diagnostic possibilities3. Suggest further EEG tests (ambulatory, telemetry etc.)

EEG interpretation

Form working hypo-thesis for expectedEEG abnormality

Assist planning ofrecording

Compile availableelectro-clinicalinformation&ensure technicaladequacy

Contribution to clinicaldiagnosis & Taxonomy

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PTgiagsacpinewnumbers (Binnie and Stefan, 1999), particularly aftersleep deprivation (SD) (Rowan et al., 1982) and vari-

igure 1.01. EEG diagnostic pathway; from the initial referral toasks and requirements in each stage of the orderly EEG processontribution. For example, individualization of the recording relihysician and the provided clinical information on the requestologist (see section 1.4 in the text). The grey boxes in the lowulminating in the important role of the EEG in clinical diagnosis

iagnostic EEG strategies are recommended, depend-ng on objectives (for instance possible presurgicalvaluation) and available resources. This level is stilllinically significant because it can guide treatmentith specific antiepileptic agents, and is also important

or clinical or epidemiological research.ote 1: When the EEG findings are abnormal,ut different to those expected from the referral,lectroencephalographers need to inform referringhysicians that findings do not support the workingiagnosis/suspicion; instead, they may suggest a dif-

erent class of epilepsy (for instance, focal instead ofeneralized), or the overall EEG/clinical evidence maye insufficient for confident classification.ote 2: A normal EEG does not have the same mean-

ng in all suspected syndromes. Although it does notxclude the diagnosis of most (Fowle and Binnie,000; Koutroumanidis and Smith, 2005), it does ren-


er unlikely the diagnosis of a few syndromes whenhe EEG recording is adequately performed, such ashildhood absence epilepsy (CAE) in an untreatedhild with reported daily pyknoleptic “absences”, whoyperventilated correctly during the EEG.

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final report. The white boxes in the upper row show the mainthe initial request to the final report to maximize its diagnosticthe completeness of the diagnostic hypothesis of the referring

, but also on additional information obtained by the EEG tech-w show the main objectives of each stage of the EEG process,taxonomy.

.4 Overview of clinical EEG practice: from thenitial request to the final report (figure 1.01)

lanning and recording the EEGhe occurrence and behaviour of diagnostic EEGraphoelements is dynamic, subject to a plethora of

nterplaying modulators that include the following:ge of the patient, stage of the natural course of theiven syndrome, time of day, state of arousal andleep adequacy, antiepileptic and other medications,nd possibly other environmental factors. The full EEGharacterization of an epilepsy syndrome may not beossible from a standard “interictal” recording dur-

ng wakefulness or even sleep; waking EEGs may showo ED in substantial numbers of people with knownpilepsy (Pedley et al., 2003; Pillai and Sperling, 2006),hile sleep EEGs may recover ED in much higher

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bly across epilepsy syndromes with the highest yieldpon awakening in generalized epilepsies (Degent al., 1987). Moreover, the occurrence of defining EDr even seizures may depend on standard activation


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such as hyperventilation [HV] that can elicit gener-lized spike-wave discharges [GSWD] or absences) orpecific activation (such as reading), the effect of whichan be tested on suspicion under controlled condi-ions in the EEG laboratory. Therefore, EEG recordingsan be “personalized” according to the diagnosticypothesis and the available clinical information, max-

mizing diagnostic yield.espite some published guidance about the structuref the EEG referral (Noachtar et al., 1999; Beniczky et al.,013), experience from both resource-limited (Birbeckt al., 2011) and developed countries (Nicolaides et al.,995; Smith et al., 2001) indicates that EEG requests mayot contain pertinent clinical information or a workingypothesis, while (not infrequently) the clinical ques-

ion is misguided (“is it epilepsy?”/“rule out epilepsy”)Fowle and Binnie, 2000; Koutroumanidis and Smith,005). Important information may be obtained dur-ng electrode application, when the EEG technologisttrained in basic epileptology) has ample time to dis-uss key clinical aspects, including seizure symptomsnd semiology (as patients are frequently escorted),requency, timing, and possible triggers with the viewo test during the recording (figure 1.01).he relevant information can be entered in a struc-ured template, together with the standard personalnd referral data, detailed recording conditions, andhe factual report (for a comprehensive list of entries,eaders are referred to SCORE [Beniczky et al., 2013]).

nterpreting and reporting the EEGEG interpretation is based on expert visual analysisf the ED and other non-epileptiform abnormalities,

ncluding their response to activation and behaviourn different states of vigilance, and then their synthe-is into a plausible diagnostic hypothesis, taking intoccount the available clinical information and possi-le previous EEG results. Early recordings can help,s robust patterns during childhood and adolescenceay become subtle and ambiguous in adulthood.

he final clinical EEG report “translates” the EEG find-ngs into clinically useful information and may suggestn epilepsy type or syndrome, implicitly with someeference to the possible aetiology and with varyingegree of diagnostic certainty (section 1.3.5). Impor-

antly, this business end of the EEG process also feedsaxonomy. The EEG report should be clear in contentsing common clinical terminology without special

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EG terms (Noachtar et al., 1999; Kaplan and Benbadis,013; Tatum et al., 2016).EG interpretation is not always straightforward. Inhe process of EEG “reading”, simple and unequiv-cal in their clinical significance, but also complexnd potentially ambiguous patterns of ED will haveo be “rephrased” using standard widely accepted

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erminology (Noachtar et al., 1999; Beniczky et al.,013), or, if this is not possible, a finite gamut ofEG descriptors; both may have important semanticonnotations. For example, a spike-and-wave dis-harge that occupies all scalp electrodes but has aegional lead-in can be interpreted as either focal withast generalization (implying focal epileptogenesis),r as generalized with an incompletely generalizednset (suggesting genetically determined generalizedpilepsy). Similarly, a lateralized spike-and-wave dis-harge that occupies several adjacent scalp electrodesan only be interpreted as either regional (Noachtar etl., 1999), or as incompletely generalized (Browne et al.,974). Although the fundamental distinction betweenfocal” and “generalized” has been partially addressedwith respect to seizure onset) in the 2010 ILAE reportBerg et al., 2010), EEG interpretation of phenomeno-ogically ambiguous interictal ED remains unresolved.herefore, this dichotomy is implicitly liable to sub-

ective expert opinions that account for the moderatenter-observer agreement (van Donselaar et al., 1992),otentially leading to double taxonomy standards.hen the available EEG evidence is insufficient for

lectroencephalographers to suggest a diagnosis with-ut being overly subjective in their opinion, it isecommended that the rationale and the EEG evidencere fully explained in the report, all diagnostic pos-ibilities are included and further testing is advisedepending on the available resources (for instance,leep or ambulatory EEG, video telemetry, etc.). Dif-erentiation between genetic (idiopathic) generalizedpilepsies and secondary bilateral synchrony (SBS) istypical example of such limitations (see relevant dia-nostic criteria in section 2.2). The roles of the referringhysician, the EEG technologist, and the electroen-ephalographer in the optimal diagnostic clinical EEGrocess are summarized in figure 1.01. It is emphasized

hat the diagnostic and taxonomic value of the EEGeport depends on the competence of each contribu-ion. Although the roles and their weightings in theEG process are different, each stage feeds the nextnd any deficiency in this flow will affect the clinicalsefulness of the final report.

.5 Levels of EEG recording

or best patient care and farthest reach, a com-rehensive EEG recording-reporting methodological

ramework should be versatile and adaptable to the


iverse levels of clinical EEG service worldwide, tak-ng into account the available material and humanesources, including the variable training and exper-ise of the clinicians who interpret EEG and the EEGechnologists alike.here is substantial variability in the provision of theEG service worldwide, reflecting the large gap in the

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pilepsy care between resource-limited countries andhe industrialized countries of Europe, North America,nd East Asia. In the former, mainly located in Latinmerica, Africa, Asia, and the Caribbean, epilepsy isot amongst the first public health priorities despite

ts high annual incidence that ranges from 92.7 to 190er 100,000, mostly in relation to preventable parasiticnd infectious diseases and under-resourced perinatalare (Carpio and Hauser, 2009); neurologists are veryew and practice in major cities (Mani, 1998), referralervices are frequently poor and people with epilepsyre often managed by primary-care physicians, oremain untreated (de Bittencourt et al., 1996). EEG ser-ices are variably available in only three quarters ofesource-poor countries (Dua et al., 2006), operatingithout minimum standards by untrained laboratory

echnologists (Radhakrishnan, 2009; Birbeck et al.,011). Digital video-EEG equipment is scarce, usuallyoncentrated in the private sector and only in majorities and hence inaccessible to the majority of theopulation (WHO, 2004, 2005; PAHO, 2011). Whenvailable in the public sector, waiting times may bextremely long (Caraballo and Fejerman, 2015) andrief recordings are common (Birbeck et al., 2011).

n Africa, although EEG services are becoming morevailable than neuroimaging (Wilmshurst et al., 2011),EG is still not routinely performed in patients hospi-alized with convulsive epilepsy (Kariuki et al., 2015a),hysicians trained to basic EEG interpretation are few,nd educational guidelines for the EEG interpretationre lacking (Kander and Wilmshurst, 2015). Well-onducted EEG studies on children and adults (Igwet al., 2014; Lagunju et al., 2015; Kariuki et al., 2015b)re still scarce and mostly concern routine recordingsn patients with convulsive seizures. Electroclinicaliagnosis primarily focuses on the distinction between

ocal and generalized epilepsy, pragmatically reflectingundamental clinical needs.ecording and reporting standards vary also amongst

he industrialized countries of Europe, North Amer-ca, and the Far East, where digital video-EEG is readilyvailable. The proportion of abnormal EEGs may dif-er between hospital- and community-based samplesBinnie and Stefan, 2003), while training of tech-ologists and recording protocols vary across EEGepartments. In some district hospitals, EEGs maye reported by clinical neurophysiologists primarily

nterested in electromyography, while at epilepsy cen-res and university hospitals, inter-observer agreement


ay only be moderate (van Donselaar et al., 1992).

e have pragmatically distinguished two levels ofEG recording, according to the available depart-ental facilities and material resources (including

apability for lengthy and sleep recordings and spe-ific activation, multiple channels, and availability

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role of EEG in the diagnosis and classification of the epilepsies

or polygraphy, synchronized video) and the skillsnd trained expertise of the EEG technologist: a)asic, suitable for most district general hospitals and

or tertiary/university hospitals in resource-limitedountries, and b) advanced, with the minimumequirements expected for tertiary epilepsy centresnd university hospitals in developed countries (box 1).he requirements for the basic level may appearore complex and demanding than those currently

mployed by many EEG departments in district generalospitals, but our primary aim is to gradually raise thetandards of practice at this level. It can be sensiblynferred that for the majority of the epilepsy syn-romes, notwithstanding some differences in materialesources, basic EEG may diagnostically offer almost as

uch as the advanced when recorded by skilled EEGechnologists with appropriate training in epileptologysections 1.1 and 1.4).o provide EEG technologists/nurses with the ratio-ale for the syndrome-specific recording protocols,e have included information about the behaviours of

D in different states of vigilance and their responseo specific and non-specific activation.

.6 EEG diagnostic and taxonomic criteria withinhe context of the revised terminology andoncepts for the organization of seizures andpilepsies (Berg et al., 2010; Scheffer et al., 2017)

he purpose of the diagnostic process in epilepsies iswofold: i) to identify the full clinical semiology andefine the epilepsy type or syndrome, and ii) to find

he underlying cause. The EEG directly contributes tohe clinical, but not to the aetiological diagnosis. A dis-inctive EEG pattern (such as a focal spike-wave) mayranscend different aetiologies, while epilepsies withingiven class of aetiology may have different EEG char-cteristics; for instance, CAE, Dravet syndrome andutosomal dominant nocturnal frontal lobe epilepsyre genetically determined and yet exhibit distinctivelyifferent EEG profiles.o fulfil its diagnostic and taxonomic role within theew framework, the EEG and essentially its effectivelinical contribution, the EEG report, should be in com-liance with the new concepts, though ensuring thateplacement of the 1989 concepts and terms will notmpact on its clinical usefulness.

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EG and clinical classificationhe syndrome approach remains the backbone of thelinical classification (Scheffer et al., 2017) and theevision of the EEG criteria at this level needs no partic-lar amendments when officially recognized epilepsyyndromes are concerned.


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Box 1. The two levels of EEG recording.A. Basic:HV and IPS (standard activating procedures).Basic EMG polygraphy (unless channels are limited).Digital machines and video (may be variably available in resource-limited countries).Recording during sleep (when difficult to schedule, encourage drowsiness/light sleep, if possible).

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HV, IPS, other specific activation, video, multichanneSleep EEG after partial (or 24-hour in some departmepharmaceutically-induced.Prolonged daytime video or overnight recordings, vidNote that all recordings can be individualized accord

EG and aetiological classificationhe 2017 ILAE position paper (Scheffer et al. 2017)n Classification of the Epilepsies recognizes a rangef aetiological groups, with emphasis on those thatave implications for treatment: structural (in the pres-nce of an MRI lesion), genetic, infectious, metabolic,nd immune, as well as an unknown group. It alsoecognizes the fact that aetiologies are not mutu-lly exclusive, a patient’s epilepsy may be classifiednto more than one aetiologic category; the aetiolo-ies are not hierarchical, and the importance given tohe patient’s aetiological group may depend on theircumstance. For instance, a patient with tuberousclerosis has both a structural and a genetic aetiology;he structural aetiology is critical for epilepsy surgery,hereas the genetic aetiology is key for genetic coun-

elling and consideration of novel therapies such asammalian target of rapamycin (mTOR) inhibitors.

he EEG per se may suggest a certain class of aeti-logy only indirectly; as a rule, such suggestion ison-specific, although some EEG patterns may imply

hat a certain aetiology is more likely than another,ntroducing a degree of probability. For instance, theombination of interictal spikes and slow wave activityver one temporal lobe in a patient with focal seizuresuggests a structural cause, although it may also occurn the rare familial temporal lobe epilepsy (Cromptont al., 2010). Similar EEG features also occur in patientsithout family history or an identifiable cause, as for

nstance, in those with normal imaging or non-specificistopathological findings and good seizure outcomefter ipsilateral temporal lobectomy (Koutroumanidist al., 2004). In this example, the good one-to-one cor-elation between the 1989 and the 2017 aetiological

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axonomies (structural vs. symptomatic, unknown vs.ryptogenic or probably symptomatic, and genetic)oes not influence the clinical usefulness of the EEGeport.owever, associations between the two aetiological

axonomies can be more complex when certain typesf idiopathic generalized epilepsy (IGE) are concerned

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ygraphy.sleep deprivation (SDEEG) or

telemetry, etc., as indicated.to clinical information/questions.

ith potentially significant clinical impact on the EEGeport. While reporting on officially recognized syn-romes of genetic generalized epilepsy (GGE), such ashildhood Absence Epilepsy (CAE), juvenile absencepilepsy (JAE), juvenile myoclonic epilepsy (JME),nd epilepsy with generalized tonic-clonic seizureslone (GTCSa), communicates exactly the same clin-cal information in either taxonomy (see EEG andlinical classification above), there may be potentiallyignificant pitfalls when patients with clinical pheno-ypes, previously understood within the spectrum ofGE, but not officially recognized as distinctive syn-romes and therefore not currently featuring within

he GGE, are concerned. Examples include the syn-romes of eyelid myoclonia with absences (ELMA)

Jeavons, 1977), absence status epilepsy (ASE) (Gentont al., 2008), epilepsy with phantom absences (E-PA)Panayiotopoulos et al., 1997), and also a numberf unclassifiable clinical phenotypes (Valentin et al.,007). They all share with the recognized geneticeneralized syndromes of CAE, JAE, JME, and GTCSahe characteristic GSWD, a genetic marker par excel-ence, and also defining seizure symptoms, such asAs, but with little evidence of substantial geneticontribution to their aetiology (as in epilepsy with PAKoutroumanidis et al., 2008]) or no evidence at all (as inSE [Genton et al., 2008]), at least according to our cur-

ent knowledge. From the EEG perspective, it would beisleading to classify some of the non officially recog-

ized IGE syndromes as of “unknown aetiology”. Forhis reason we classified them as “possibly genetic”table 1).similar adjustment was felt necessary for the group of

diopathic (self-limited) focal epilepsies of childhood,or which conclusive evidence for primary genetic aeti-


logy is still elusive (Vadlamudi et al., 2014). Again, thelinical usefulness of the EEG report is not affectedhen typical electroclinical forms of the three offi-

ially recognized main syndromes (benign Rolandicpilepsy, Panayiotopoulos syndrome, and occipitalpilepsy of Gastaut) are concerned, but intermediate

CBKiemelés


E


Table 1. Main EEG patterns in the 2017 aetiological taxonomy of the epilepsy syndromes and epilepsies.

Genetic Possibly Genetic† Unknown Structural and Other††

EPILEPSIES WITH GENERALIZED SEIZURES*

– GSWD >2.5 Hz(variations acrosssub-syndromes)– Non-localizingfocal spikes– Normalbackground

– CAE– JAE– JME– GTCSa– Reflex(photosensitive)

– Absence epilepsy< 3 years– Eyelid myoclonia– Myoclonic-atonic– Epilepsy withphantom absences– Absence statusepilepsy– Unclassifiedphenotypes

– GSWD < 2.5 Hz &gen. bursts ofpolyspikes/fast insleep– Diffusely slowbackground

Lennox-Gastautsyndrome




– GSWD of variablefrequencies– Focal/multifocalspikes– Diffusely slowbackground

– Formersymptomaticgeneralizedepilepsies/epilepticencephalopathies,including most casesof Lennox-Gastautsyndrome– Progressivemyoclonicepilepsies**

EPILEPSIES WITH FOCAL SEIZURES*

– Focal spikes ofsyndromeor lobe specifictopography– Normalbackground

– BFIS– ADNFLE– Familial mesial TLE– Familial lateral TLE

– Reflex (hot water)

– Focal spikes ofsyndrome specifictopography– GSWD >2.5 Hz mayoccur– Normalbackground

– Gastaut (&photosensitive) OLE– Panayiotopoulossyndrome– Rolandic epilepsy– Intermediatephenotypes


– Atypical benigfocal epilepsy

241

n


2


Table 1. Main EEG patterns in the 2017 aetiological taxonomy of the epilepsy syndromes and epilepsies.

Genetic Possibly Genetic† Unknown Structural and Other††

– Focal spikes ± focalslowing of syndrome(lobe) specifictopography– Normal orabnormalbackground

– Focal (formercryptogenic)epilepsies

– Spikes ± focalslowing of lesionrelated topography– Rarely SBSBackground normalor abnormal

– Mesial TLE– Post-trauma,infection, stroke,neoplasms,autoimmune– Corticalmalformations***– Tuberoussclerosis**

EPILEPSIES WITH FOCAL AND GENERALIZED SEIZURES

– Syndrome-dependent patternsof spike-wave

– Dravet syndrome – Reflex(photosensitivity,reading,FOS, video games)

– Normalbackground

– FS+ phenotypes

The syndromes presented are examples for each major diagnostic EEG pattern and by no means form a comprehensive list.†“expanded” genetic group for the purpose of the EEG report to retain its clinical usefulness when not recognized syndromes orunclassifiable clinical-EEG phenotypes of idiopathic generalized epilepsy (IGE) are concerned (discussed in the last section of theIntroduction); †† including infectious, metabolic and immune aetiologies; *focal ictal symptoms/signs and rarely focal seizures mayoccur in the group of the genetic (idiopathic) generalized epilepsies, while absences may occasionally occur in the group of possiblygenetic self-limited focal epilepsies of childhood; **epilepsies part of a genetic disorder; ***polymicrogyria may also be secondary togC sy; GG fantie sy; Fb

ps(gafrasewao2o

u(haAiait

ene mutations.AE: childhood absence epilepsy; JAE: juvenile absence epilepSWD: generalized spike-wave discharge; BFIS: benign familial inpilepsy; TLE: temporal lobe epilepsy; OLE: occipital lobe epilepilateral synchrony.

henotypes of similar aetiology that cannot be clas-ified in any of the three main syndromes do existCovanis et al., 2003). From the EEG perspective, aenetic substrate was suspected 50 years ago (Braynd Wiser, 1964, 1965) and is supported by evidencerom linkage and association analysis of centrotempo-al spikes (Neubauer et al., 1998; Strug et al., 2009; Pal etl., 2010) and the close association between these focalpikes and GSWD in many of these children. The rel-

42

vant proportions of GSWD reach a third of childrenith idiopathic occipital epilepsy of Gastaut (Gastaut

nd Zifkin, 1987; Caraballo et al., 2008), up to a quarterf those with Panayiotopoulos syndrome (Ohtsu et al.,003; Specchio et al., 2010) with some children showingnly GSWD at seizure onset (Caraballo et al., 2015), and

Teuidp

TCSa: generalized epilepsy with tonic clonic seizures alone;le seizures; ADNFLE: autosomal dominant nocturnal frontal lobeOS: fixation-off sensitivity; FS: febrile seizures; SBS: secondary

p to 15% of children with benign rolandic epilepsyBeydoun et al., 1992); a few of these children may evenave absences (Gastaut and Zifkin, 1987; Caraballo etl., 2004).n “expansion” of the genetic group to include all the

diopathic focal epilepsies and the IGE syndromes thatre not officially recognized was deemed the only sat-sfactory way to maintain the clinical-taxonomic role ofhe EEG.


able 1 shows examples of epilepsy syndromes andpilepsies for each major diagnostic EEG pattern, tab-lated according to the main aetiologies, with the

mportant caveat that aetiological classification is aynamic process and that future research is antici-ated to demonstrate varying genetic contribution in


E

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number of epilepsies and syndromes currently con-idered of unknown aetiology. In table 1, the idiopathicocal epilepsies of childhood and adolescence andhe non-recognized IGE syndromes and phenotypeseature under the subheading of “possibly genetic”,tressing their EEG links to the four major syndromes ofGE. We emphasize that this organization serves EEGurposes and is in keeping with the freedom of orga-izing epilepsies according to a defining feature that

s useful for a particular purpose (Berg and Scheffer,011), in this case the GSWD. Accordingly, ELMA,pilepsy with PA, ASE, patients with unclassifiable IGE,nd at least a subset of children with absences beforehe age of three years or with epilepsy with myoclonicbsences are possibly genetic with mainly general-zed seizures and EEG abnormalities; the idiopathicocal epilepsies of childhood are possibly genetic, self-imited epilepsies with mainly focal seizures and EEGbnormalities; and the idiopathic reflex epilepsies areenetic (photosensitive epilepsy) or possibly geneticreading/language-induced epilepsy) with generalizednd focal seizures and EEG abnormalities (table 1). Tovoid confusion, and also to limit the social stigmand consequences that may exist in different coun-ries and cultures (Scheffer et al., 2017), both termsgenetic generalized epilepsy” (GGE) that include theexpanded” possibly genetic epilepsies and IGE will besed together as GGE/IGE throughout this document.

. Genetic (idiopathic) generalizedpilepsies (GGE/IGE)

.1. Typical EEG features - attributes and dynamics

he generalized spike-wave discharge (GSWD)t >2.5 Hzhe interictal EEG hallmark of the GGE/IGEs is theSWD at >2.5 Hz, occurring against normal back-round activity. Incomplete GSWD and non-localizingocal spikes may variably occur.

he GSWD: morphology and distribution.he GSWD consists of regular or almost regularequences of bilateral synchronous spike-and-waveomplexes at the classic frequency of 3-3.5 Hz (mea-ured after the first second of the discharge), or fastert 4-5 Hz. Frequency may be faster and irregular atts very onset (within the first 500 ms-1 sec), gradu-


lly slowing down towards its termination, althoughntra-discharge irregularities may occur. The spikeomponent, prominent at onset, may become incon-picuous towards the end of the paroxysm. Themplitude of the spike-wave complexes is typicallyaximal over the frontal areas and displays an

pilrPc


nterior to posterior gradient, frequently fading overhe occipital areas.he term “generalized” indicates that the paroxysmccupies all areas of the cerebrum (visible over allEG leads), while the term “incompletely generalized”Browne et al., 1974) describes discharges that occupyt least two lobes on each side.oltage asymmetries between the hemispheres or anyegional (anterior, posterior, or lateral, lateralized orot) lead-in may occur; when lateralized, the regional

ead-in typically switches sides in the same or succes-ive recordings. A lead-in consistently lateralized to theame side is not necessarily an exclusion diagnosticriterion for GGE/IGE in its own right (Lombroso, 1997)see also section on SBS [2.2]).

ffect of sleep and other activation.low (non-REM) sleep, mainly Stages 3 and 2 and to a

esser degree Stage 1, activates GSWD, although Stageis rarely reached in outpatient sleep EEG recordings;ischarge activation is particularly enhanced whenleep is achieved by SD (Degen et al., 1987). GSWDend to acquire a polyspike component (GPSWD)nd become shorter in duration, incomplete or frag-ented (figure 2.01). GSWD usually attenuate or are

nhibited during REM sleep. GSWD are typically acti-ated after awakening, irrespective of the time of theay. HV usually provokes GSWD for the period of thexercise and shortly after, although the effect variescross GGE/IGE syndromes and may not be evident inll patients. Specific triggers may include photic stim-lation (and eye closure), reading and other linguisticctivities, thinking, and elimination of central visionnd fixation (see sections on reflex seizures and epilep-ies in chapter 4).

eneralized spike-wave discharges and typicalbsences.SWD/GPSWD may occur in association with demon-

trable behavioural changes, such as impairment ofonsciousness (IoC), motor and autonomic manifes-ations on video and polygraphy, or be subclinical.he length of the GSWD is not relevant to the degreef IoC (Shimazono et al., 1953), although the latter

s easier to appreciate by simple clinical observa-ion in lengthier absences. Elegant early experimentsave shown that impairment of responsiveness (as a

243

aroxysm-controlled auditory stimuli occurs and max-mizes within the initial 0.5 sec of the GSWD in ateast 80% of the discharges, while starts to graduallyecover after 1.5 sec from discharge onset (Porter andenry, 1973; Browne et al., 1974; Blumenfeld, 2012); onareful clinical assessment, mild IoC or mild but clear


2


Box 2. Assessment of consciousness during GSWD

Clinical basic: Explain the procedure before starting the recording. Give simple commands and auditory stim-uli (numbers or words) clearly and loudly as soon as possible after the onset of the discharge and repeatduring the absence, depending on its length. Check for possible direct responses during the discharge and,immediately after its offset, ask patients to repeat what they were told. The method is sensitive only forabsences associated with severe IoC/responsiveness. Recommended first-line assessment of spontaneousand HV-induced discharges longer than 3-4 seconds (shorter discharges may already be fading by the time ofthe first stimulation).

Clinical advanced: Ask the patient to perform a simple motor task - counting breaths during HV or tapping -repetitively and at a comfortable rate (Giannakodimos et al., 1995). The method aims to demonstrate defectiveconcentration or motor execution (hesitations, delays, repetition of the same number) in very brief (∼1.5-2-sec)GSWD (figure 2.03) or longer but mild absences, in which clinical basic assessment has been unremarkable(figure 3.20 and figures 3.36 and 3.37). This can be performed in all subjects older than five years of age,

o mir pe

PT)ppli

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irrespective of their level of education. Although videclosely observe patients and accurately annotate the

Clinical research: Continuous Performance Tests (Creception of information, and motor output. CPT is a

otor hesitancy can be identified in GSWD of just 2 secKoutroumanidis et al., 2008; Sadleir et al., 2009). IctaloC is milder when the associated GSWD is incom-lete (Browne et al., 1974), or asymmetric. There ismpirical evidence that IoC may also depend on therequency and regularity of the GSWD; it is typicallyevere in association with the regular 3-Hz GSWD inAE and JAE and appears milder in association with

he faster GSWD as in JME, or the slower frequencyn atypical absences (table 1). Motor manifestationsnclude head and eye retropulsion, regional (eyelid,acial, and upper limb) myoclonus, facial (typically peri-ral/oroalimentary) and limb automatisms, and less

requently automatic speech.here is no universally agreed definition of the TAeizure, as IoC, its sine qua non element, can varyidely not only in terms of severity, but also in termsf the constituents of consciousness that are involved

i.e. attention or memory), the detection of whichepends on the method used (simple observation of

he patient “blinking and staring”, unresponsivenesso verbal stimuli given during the discharge or no recallfter the end of the discharge, discontinuation or fal-ering in breath counting during HV or other simpleepetitive motor tasks, continuous performance tests,tc.) (box 2).

ormal background

44

ormal background is expected by default. In theresence of GSWD, as defined above, diffusely slowackground activity may still be compatible withGE/IGE when a reversible cause for such slowing

an be demonstrated or assumed, including toxicityith antiepileptic or other drugs (such as neuroleptics,

ithium, MAO inhibitors, and tricyclics) and coexisting

GGa

Ai(

onitoring is desirable, trained EEG technologists canrformance on basic digital or paper recordings.

use visual or auditory stimuli to assess attention,cable only in fully co-operative patients.

onditions (such as metabolic derangements orypothyroidism, postictal suppression, etc.). In suchases, background normalizes after the removal of theffensive factor.

on-localizing focal or multifocal spikeshese may occur variably over anterior, posterior, or

ateral temporal regions (Seneviratne et al., 2014). Theerm “non-localizing” distinguishes them from theD of stable (“localizing”) epileptic foci that relateo structural causes. Typically, topography is frontalsupplementary figure 2.01) or occipital, but unstable,witching sides in the same or successive recordings,r multifocal. A stable topography, even in succes-ive recordings, may still be compatible with GGE/IGELombroso, 1997) when not associated with regionalackground disturbance (supplementary figure 2.02)

for section on SBS [2.2]).

linical Practice Statement: in the appropriate clinicalontext, these EEG features can indicate the diagnosisf GGE/IGE with the highest degree of certainty. TheEG report may further suggest a particular age-relatedub-syndrome according to particular EEG/video-EEGndings (see specific GGE/IGE syndromes).

.2. EEG features that, in the presence of >2.5-Hz


SWD/GPSWD, may indicate coexistence ofGE/IGE and focal epilepsy of structural or other

etiology, or secondary bilateral synchrony (SBS)

consistent (stable) focus of spike or sharp wave activ-ty, associated with regional background disturbancei.e. irregular slowing with or without some attenuation


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f fast rhythms). Such consistent focal abnormalitieshould not be attributable to other causes, such asoncurrent cerebrovascular (vertebrobasilar) insuffi-iency (Niedermeyer, 1963), or other lately acquiredrain insults. Focal epileptic abnormalities of suchorphology and consistency raise the possibilities of

) SBS, or b) concurrent structural epilepsy with focaleizures (supplementary figure 2.04).SWD against an otherwise unexplained diffusely

low background raise the suspicion of epilepticncephalopathy, particularly when associated withubnormal cognitive function and their frequency ist, or close to, the lower end of the GGE/IGE spectrum≤2.5 Hz).

GE/IGE vs. Secondary Bilateral Synchrony (SBS)lthough frequently referred to, SBS has rarely

eceived critical analysis, and defining neurophysi-logical evidence is conspicuously absent. For theurpose of the present revision the clinical-EEG phe-omenon of SBS is operationally defined as a bilateralynchronous (generalized) spike-wave discharge (SBS-SWD) that appears to be triggered by a stablepileptogenic focal abnormality (as defined above);uch causal association can be reasonably assumedhen the stable focal abnormality has consistently the

ame topography with the lateralized/regional lead-n of the GSWD (spatial constraint), or when focalharp activity leads in a SBS-GSWD (temporal con-traint). With regard to the spatial constraint, it is theersistence of the topographic concordance between

he focal discharge and the lead-in of the GSWD thatistinguishes SBS from the typically variable associa-

ion between focal discharges and “onsets” of GSWDn GGE/IGEs. With regard to the temporal constraint,lume and Pillay (1985) required sequential ED lead-

ng to SBS-GSWD to occur for at least 2 seconds, andhe morphology of the focal triggering ED to clearlyiffer from that of the bisynchronous paroxysm, and

o resemble that of other focal spikes from the sameegion (supplementary figures 2.05, 2.06 and 2.07). Inheir study, SBS-GSWDs were slower than 3 Hz in threeuarters of the patients, most of whom had frontal

obe foci.uch obvious EEG evidence may be lacking in someases of presumed SBS; cortical foci may lie withineep sulci impeding recording of the triggering focalD, or secondary generalization may be rapid. Corrob-


rative clinical features for SBS may include frequentr predominating nocturnal seizures, focal seizures,nd sub-normal cognitive state, while brain imagingay provide important diagnostic clues (supplemen-

ary figure 2.08).ccasionally, tumours may underlie regular 3-Hz SW

Ajmone-Marsan and Lewis, 1960; Raymond et al.,

twb

Cco


995). In such cases, the overall association betweenSWD (and sometimes TA) with focal brain pathol-gy is uncertain; a lack of clear EEG evidence of SBSay be either coincidental, reflecting mere coexis-

ence of symptomatic focal epilepsies with IGE, ore due to the strategic position of the lesion in

he midline (Tükel and Jasper, 1952; Bancaud et al.,974), perhaps in some association with a geneticredisposition. Caution is needed to avoid confu-ion between SBS and the diffuse discharge from

single parasagittal generator whose field extendscross the midline. Distinction of SBS requires theemonstration of two independent but synchronouslyring foci that occupy homologous brain areas, shown

n coronal montages that employ midline electrodesDaly, 1997).

linical Practice Statement: in the presence of thebove temporal and spatial EEG constraints and withinhe appropriate clinical context, the EEG report shouldxplain the evidence and indicate the high probabilityf SBS, particularly when there are suggestive imag-

ng findings. Depending on the available resources,lectroencephalographers may also recommend fur-her EEG diagnostics, including ambulatory EEG andideo telemetry (to record focal seizures), or referralo a tertiary epilepsy centre and for brain imaging.

t is acknowledged that confident EEG differentiationetween GGE/IGE and SBS may be impossible in aumber of patients with “intermediate” EEG findingsnd complex/atypical (or unknown) clinical features. Inuch cases, it is recommended that electroencephalo-raphers recognize the diagnostic limits of the EEGnd strive to avoid unduly subjective opinions; instead,he EEG report should present the evidence and dis-uss the diagnostic possibilities, and advise furtherEG/imaging diagnostics, as above.

oexistence of genetic generalized and focalpilepsy of structural/metabolic aetiologyuch coexistence is expected to produce a complexicture with the relevant clinical and EEG characteris-

ics being recognizable when sought (Koutroumanidist al., 1999; Radhakrishnan et al., 2011). From theEG viewpoint, subclinical GSWD or TAs and/oryoclonic seizures (MS), with or without non-

ocalizing focal or multifocal spikes, should occur

245

ogether with a stable focus over a cerebral lobeithout consistent temporal or spatial associationsetween them.

linical Practice Statement: In the appropriate clinicalontext, the EEG report should indicate the possibilityf coexistent focal epilepsy, explain the evidence, and


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uggest video telemetry to record focal seizures andrain imaging, or referral to epilepsy centres with such

acilities (see sections on focal epilepsies).

. Syndromes of Genetic Generalizedidiopathic) Epilepsies

his section includes the four main and officially rec-gnized syndromes of GGE (Scheffer et al., 2017),amely, CAE, JAE, JME, and epilepsy with GTCS-a. Itlso contains a number of distinctive electroclinicalhenotypes that, over the last few decades, haveeen well documented in the peer reviewed literatureithin the IGE spectrum. These are also characterizedy the “genetic EEG marker” of GSWD and herein com-lement the four main syndromes as possibly geneticeneralized epilepsies (see introduction).

.1. CHILDHOOD ABSENCE EPILEPSY (CAE)

verviewAE is the archetype GGE/IGE syndrome of child-ood onset absences, associated with the “classic”-4-Hz GSWD on the EEG. It affects neurologicallyormal children, the majority of which are girls. TAstart between 4 and 10 years of age, with a peakt 5-7 years, and in most children, remit in earlydolescence. Infrequent GTCS may occur later in ado-escence or adulthood, but not before or during thective phase of absences. MS are not a feature of CAE.heir early occurrence in a child newly diagnosed withbsences may instead indicate JME of pre-adolescencenset, with absences as the first seizure type; a

ater occurrence may denote transition of CAE toME, although the timing for this transition remainso be ascertained. Other absence GGE/IGE pheno-ypes during childhood, such as absences beforehe age of three years and photosensitive epilepsyith photically-induced absences are not included

n this section; these are discussed in the respectivehapters.

eizures: symptoms and semiologyypical absences (TA). In untreated children, TA occuraily with a tendency to cluster in great numbers

hence the classic term “pyknolepsy” from ��ó�eaning “dense” and ��́�� meaning “take hold

f”); they are typically provoked by HV without dif-

46

culty. Indeed, the diagnosis of CAE is seriouslyoubted in an untreated child with reported frequentlank spells, who does not have absences duringell-performed HV. Onset is sudden with arrest of

oluntary activities, although perseveration of someemi-voluntary preictal behaviours may linger for aew seconds into the absence. Most TA last up to

osEnoOu

0 seconds and are typically associated with severeoC/responsiveness; eyes become vacant, staring orrifting upwards, and eyelids may blink. Such TA areommonly referred to as simple, as opposed to thosessociated with automatisms that are commonly calledomplex. De novo automatisms occur in the majorityf TA and relate to the duration of seizures, and areresent in up to 95% of those longer than 16 seconds

Penry et al., 1975); automatisms are oroalimentary,anual or speech, usually in this order of frequency

nd time of occurrence after seizure onset, and may beateralized but not stereotyped. Bilateral clonic move-

ents of the eyelids or face, head turning, autonomichanges, and reduction of muscle tone can occur, butre mild and do not persist throughout the seizure.udden and sufficiently loud auditory stimuli (callingchild’s name or clapping of hands) may interrupt

he absence. Offset is also sudden with resumption ofhe preictal activities as though the latter were nevernterrupted. There are no postictal symptoms.

eneralized tonic-clonic seizures (GTCS) are notxpected early in the active absence phase. Their earlyccurrence may indicate a poor prognosis (Trinka etl., 2004).

EG sectionackground. Normal; occipital intermittent rhythmicelta activity (OIRDA) can occur (see below).

nterictal paroxysmal abnormalities.uring wakefulnessiven that HV can reliably provoke TA in untreated

hildren with CAE, the diagnostic significance of inter-ctal ED is commonly superfluous. Subclinical 3-3.5-Hz

SWD are brief (although as already mentioned inhe introductory section on GGE/IGE, some distur-ance of cognition can be shown in GSWD as short assec) showing frontal-central or less frequently pos-

erior dominance. Onset is bilateral synchronous, butegional (usually frontal or occipital) bilateral or lat-ralized onsets are not infrequent, typically switchingides in the same or subsequent recordings.pike-and-wave discharges may be incompletelyeneralized or even focal, typically frontal or fron-otemporal, but also posterior (occipital or parietal),gain switching sides and location in the same orubsequent EEGs (Holmes et al., 1987; Mariani et al.,011). Their topography may be similar to the regional


nset of the GSWD, but such concordance is notuggestive of focal epilepsy with SBS as long as theEG and clinical diagnostic criteria for the latter areot met (supplementary figure 3.01) (see also sectionn SBS [2.2]).IRDA is often closely associated with CAE, partic-

larly when fast at 3-4 Hz (Watemberg et al., 2007).


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t can be intermixed with “occult” spikes in at least0% of children, enhances with HV, and sometimesvolves into the GSWD-associated TAs (supplementarygure 3.02).uring sleep

n general, sleep recordings in CAE are sparse as wak-ng EEG with adequate HV is usually sufficient foronfident diagnosis. GSWD become more frequentnd brief (fragments of the longer discharges duringakefulness) in Stages 2 and 3, and may acquire a

lear polyspike component, although less than in JME.ocal discharges may become more apparent duringleep (supplementary figure 3.03) (Koutroumanidis etl., 2012).

EG paroxysms that accompany ictal events.ypical Absences (TAs). onset and morphology of theypical 3-4-Hz GSWD as above; it is emphasized that theSWD may be faster, asymmetric or asynchronous in

he first 500 ms-2 sec, and sometimes with a polyspikeomponent with ≤three spikes, particularly at onsetsupplementary figure 3.04).A can “start” conceivably from the occipital areas, fol-owing a run of OIRDA (supplementary figure 3.02), orrom the frontal areas, not infrequently in the samehild (supplementary figure 3.05).he duration of absences varies from two to usu-lly less than 20 seconds. Following the briefpening phase, the intra-discharge frequency isegular with gradual smooth decline; occasionalrief interruptions may occur spontaneously or inesponse to auditory stimuli (supplementary fig-re 3.06), however, no irregular fragmentations occurs in JME. Sometimes the opening phase maye more prolonged, or asymmetric (supplementarygure 3.07).or myoclonic seizures that may signal transition toME, see relevant chapter.

typical EEG/video EEG features.(1) Generalized polyspike-wave discharges (with

three spikes per wave) during wakefulness.(2) Marked variations of the intra-discharge fre-

uency or fragmentations during wakefulness.(3) Prominent photosensitivity with photically-

nduced absences clearly outnumbering possiblepontaneous or HV-induced absences; consistent


ssociated eye closure paroxysms.(4) Prominent myoclonic features occurring through-ut the absences (eyelid or other facial, head, body, orxtremities), rhythmic or arrhythmic.

(5) Prominent tonic or atonic component associ-ted with polyspikes or EEG flattening (shown by EMGolygraphy).

bBriaff


ecording protocolsasic level

In untreated children with CAE, absences arexpected to occur during or immediately after HV. Ifideo is not available, EEG technologists should care-ully observe the children throughout the absencesnd try to note any associated behavioural changes (forecommended stimulations during the absences, seessessment of consciousness/responsiveness belownd box 2).

Activation: HV (with the child sitting up and armsutstretched forwards) performed twice or more ifeeded using a toy windmill to blow on in youngerhildren; IPS.

Use bilateral deltoid EMG polygraphy if enoughhannels are available.dvanced level

Activations: HV as in basic level; video record-ng allows full documentation of the associated ictalehavioural changes; IPS.Bilateral deltoid EMG polygraphy is mandatory.As absences are easily provoked by HV, recordings

uring sleep are not required for the vast majority ofhildren with CAE. When needed (see main indica-ions below), facilitate sleep by partial SD, attempt toeach Stage 2 for at least 15-20 minutes (if possible,tage 3 also), then record for at least 30 minutes afterwakening, including HV and IPS, as above.ssessment of consciousness/responsiveness duringSWD (box 2).linical basic. Essential, and probably sufficient, asAE is defined by absences associated with severe

oC/unresponsiveness.linical advanced. This may be redundant for clinicaliagnostic purposes if basic assessment demonstratesAs. It is doable at both recording levels, with the addi-ional benefit of detailed video analysis at advancedevel.mmediately after each absence, children should besked to repeat the given auditory stimuli and be ques-ioned about possible symptoms.

evels of EEG diagnosis) Confirmatory of CAE (based on clinical suspicionf CAE in untreated children). Recording of TAs with

he typical ictal and interictal presentation; no atypicallinical or EEG features. There is no clinical need toerform advanced sleep-deprived recording (for both

247

asic and advanced waking recordings).) High diagnostic certainty (probable). No TAsecorded, but typical interictal presentation; no atyp-cal clinical or EEG features (for both basic anddvanced waking recordings). Note that it is unusualor HV not to activate TA, unless if sub-optimally per-ormed. In this scenario, findings are supportive of


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AE, but advanced recording during sleep after partialleep deprivation (SDEEG) with >1 session of HV onwakening is recommended to record and study TAsnd move diagnostic certainty up to the confirmatoryevel A.

ote 1: if still no TAs are recorded during sleep-eprived advanced EEG that contains typical interictal,ith or without some atypical, EEG features, a diag-osis of CAE is no longer acceptable. Findings maytill be consistent with GGE/IGE, including absencesgiven the history), but are not suggestive of CAE. Inery young children, consider other diagnostic possi-ilities, including glucose transporter type 1 deficiencyyndrome (see also chapter on absences with earlynset), especially if absences are drug resistant.ote 2: In the untreated child with suspected absences,

he diagnosis of CAE can be excluded when the EEGemains normal despite satisfactory HV, particularlyhen sleep-deprived recordings are concerned.

ndications for performing or repeatingleep-deprived advanced EEG or prolonged videoecording.(1) Failure to record absences (at basic and advanced

EG levels).(2) Persistent occurrences of focal spikes and focal

nsets of absences over a single area.(3) Atypical features during wakefulness (at basic

nd advanced EEG levels), particularly in very younghildren.(4) Resistance to appropriate AEDs (VPA, LTG, ESX).(5) GTCS or MS of early onset, or a history of possible

ocal seizures.

.2. JUVENILE ABSENCE EPILEPSY (JAE)

verviewAE is the main absence syndrome of adolescence,lthough onset can range from around eight yearstherefore overlapping with that of CAE) to early adult-ood. Onset peaks between 10 and 13 years of age.oth sexes are equally affected. GTCS occur in the vastajority of patients, and MS in about 15%. JAE is notself-limiting syndrome, but satisfactory seizure con-

rol with appropriate pharmacological treatment cane achieved in the majority of patients (Trinka et al.,004; Hirsch et al., 2007; Wirrell, 2013).

48

eizures: symptoms and semiologys in CAE, absences are usually associated withevere disturbance of consciousness/responsivenessnd automatisms, and are provoked by HV, however,hey occur less frequently than in CAE, and usually spo-adically at any time of the day without tendency toluster.

wofr(eM

n contrast to CAE, GTCS often occur early during theatural course, and may even be the first overt seizure.hen present, MS are infrequent and usually occur

poradically any time during the day.

EG sectionackground. Normal.

nterictal paroxysmal abnormalities.uring wakefulnessSWD, incompletely generalized and focal SWD with

ctivation by HV occur, as in CAE. There may be morevident polyspike component (>3 spikes per wave),ut a constant relationship with the associated slowave is usually maintained.uring sleepischarges become more frequent and brief with annhanced polyspike component during Stages 1 and 2f non-REM sleep (supplementary figure 3.08) and evenriefer, typically consisting of single spike/polyspikend wave complexes in Stage 3 (supplementary fig-re 3.09) (Sadleir et al., 2009). GSWD attenuateuring REM periods, but may persist, particularly inatients with treatment-resistant JAE (supplementarygure 3.10). Brief regular GSWD may occur duringleep, but the frequency is usually slower than in wake-ulness (compare GSWD in supplementary figures 3.11nd 3.12).

EG paroxysms that accompany ictal events.ypical absences. Onset, morphology of the associatedlassic 3-3.5-Hz GSWD, and termination occur as inAE; duration varies but seizures may be longer than

n CAE, sometimes exceeding 30 sec (supplementarygure 3.13).bsences are associated with severe IoC (supplemen-

ary figure 3.13), but in general, they are consideredess severe than in CAE (supplementary figure 3.11).here may be a more evident polyspike component>three spikes per wave), but unlike JME, a constantelationship with the associated slow wave is usually

aintained (Panayiotopoulos et al., 1989a).iven the typically long duration of absences in JAE,

utomatisms are frequent, as in CAE (supplementarygure 3.14).eneralized convulsions. These may occur indepen-ently or follow an absence (absence-tonic-clonicequence) with transition from the classic 3-Hz spike-


ave GSWD to the pattern of generalized fast rhythmsf the GTCS (supplementary figure 3.15). The actual

requency of this sequence is uncertain because longecordings that are more likely to record a GTCSsuch as inpatient video telemetry) are infrequentlymployed in patients with GGE/IGE.yoclonic seizures: as in JME (see next section).


E

The

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typical EEG/video EEG features.(1) Consistent irregular discharge fragmentations

uring wakefulness.(2) Discharges of fast rhythms/polyspikes (either at

he onset, within the GSWD or independently) duringakefulness (supplementary figure 3.16).

(3) Prominent photosensitivity with photically-nduced absences clearly outnumbering possiblepontaneous or HV-induced absences; consistentssociated eye closure paroxysms.(4) Prominent myoclonic features occurring through-ut the absences (eyelid or other facial, head, body orxtremities), rhythmic or arrhythmic.(5) Prominent tonic or atonic component (on video,

ut appropriately shown by EMG polygraphy), associ-ted with polyspikes or EEG flattening.

ecording protocolsasic levelIn untreated patients with JAE, absences or GSWD

re expected to occur during or immediately after HV,erformed with the patient sitting up with arms out-tretched or standing; the exercise can be performedwice, or more if needed. If no absences occur, encour-ge light sleep when time allows, and repeat HV afterwakening, as above. If video is not available, EEGechnologists should carefully observe the patient forhe duration of the GSWD and annotate any asso-iated behavioural changes as fully as possible (forecommended stimulations during the absences, seessessment of consciousness/responsiveness belownd box 2).IPS.Use bilateral deltoid EMG polygraphy if enough

hannels are available.dvanced level

At this level, and particularly for older patientsn treatment, SDEEG is recommended for initialssessment. If a waking recording has been alreadylanned, encourage light sleep, provided that timellows.Bilateral deltoid EMG polygraphy is mandatory.Activation with IPS and HVV as in basic level on

wakening : HV more than twice if needed. Assessonsciousness/responsiveness during discharges (seeelow and box 2). In partially sleep-deprived EEG, try

o reach Stage 2 and maintain sleep for at least 15-20


inutes, if possible, record for at least 20-30 minutesfter awakening, including HV.n both recording levels, patients can be ques-ioned about possible symptoms immediately after anbsence.ssessment of consciousness/responsiveness duringSWD (box 2).

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linical basic. Essential, and probably sufficient, asAE is defined by absences associated with severeoC/responsiveness. Immediately after each absence,atients should be asked to repeat the given auditorytimuli (and be questioned about possible symptoms,s above).linical advanced. This may be a redundant step ifbsences are demonstrated by basic assessment, ast usually happens in newly diagnosed, drug-naïveatients. However, it may be useful in older adults, whoay have milder/briefer absences, particularly when

hey are already on treatment.

evels of EEG diagnosis) Confirmatory of JAE (based on clinical suspi-ion of JAE in untreated children/adolescents/adults).ecorded TAs with the typical ictal and interictal pre-entation, without atypical clinical or EEG features.here is no clinical need to perform advanced sleep-eprived recording (for both basic and advancedaking recordings), however, see clinical indications

or SDEEG below.) High diagnostic certainty (probable). No TAsecorded, but typical interictal presentation; no atyp-cal clinical or EEG features (for both basic anddvanced waking recordings). Note that, in contrast toAE, HV may not always activate TA in JAE; therefore, in

he presence of suggestive history and typical interictalEG findings, the diagnosis of JAE is still highly prob-ble. Nevertheless, advanced recording during sleepfter partial SD with >1 session of HV on awakenings recommended to record and study TAs and moveiagnostic certainty up to the confirmatory level A.) Low diagnostic certainty (possible). Typical, but alsony of the atypical, video-EEG/EEG features, as abovefor both basic and advanced recording levels): find-ngs are consistent with GGE/IGE, but not suggestive ofypical JAE. An atypical presentation of JAE is still possi-le, and prolonged advanced level SD EEG recording orideo telemetry is recommended to explore the wholelectroclinical picture.ote: normal basic or advanced level EEG does notegate a diagnosis of JAE when clinical history isuggestive. Proceed with, or repeat, advanced levelD EEG.

ndications for repeating advanced SD recording.(1) Failure to record absences in basic or advanced

249

aking EEGs.(2) Resistance to first-line AEDs (i.e. VPA, LTG).(3) Clinical evidence of new-onset myoclonic jerks.

ndications for video telemetry.(1) Failure to record absences in repeated advanced

evel SD EEG recordings.


2

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–a(–s

3

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(2) Atypical presentation (see diagnosis level Cbove) or clinical suspicion of additional seizure typei.e. with focal features).

(3) Clinical suspicion of non-convulsive (absence)tatus.

.3. JUVENILE MYOCLONIC EPILEPSY (JME)

verviewME is the main myoclonic syndrome of adolescencend one of the most typical epilepsy syndromes. Onsetan range from before the age of 10 (therefore over-apping with that of CAE) to mid-20s, or even later.

S, typically occurring on or after awakening, are theefining seizure and can be the only seizure type inome patients. GTCS occur in most patients and mildbsences in about a third when video-EEG is opti-ally used. SD, early or forced awakening, and stress

re principle precipitants for MS and GTCS. In manyatients, JME is not self-limiting; response to appro-riate antiepileptic medication is in most patientsatisfactory, although it is generally deemed inferior tohat of JAE with a probably greater risk for relapse whenntiepileptic treatment is stopped (Panayiotopoulos etl., 1994; Kasteleijn-Nolst Trenité et al., 2013).

eizures: symptoms and semiologyhe characteristic spontaneous MS are typicallyescribed as more or less symmetric brief sudden

erks of mainly the shoulders and upper arms, whichwhen strong - may cause abduction and flexion of

he upper limbs at the elbow and of the lower limbswhen involved) at the hip and knee, with associ-ted extension of the neck (supplementary figure 3.17).owever, topography and laterality may vary and MSay be mild and only felt rather than seen, predomi-

ate on one side, or involve the distal parts of the upperimbs. Indeed, some patients describe their jerks asnilateral or even focal, not infrequently misleading

o a diagnosis of focal epilepsy, particularly whenn EEG is not performed, is sub-optimally recordedr poorly interpreted. Typically, MS occur within therst couple of hours after awakening, either in theorning or after a daytime nap; they occur as soli-

ary events or in clusters, particularly upon early ororced awakening after a night of short or poor sleep,r during evening relaxation. Triggers include move-ents (praxis-induced) in a sizable number of patients,

50

hotic stimulation in a tenth, and reading or other lin-uistic activities in a few (Oguni et al., 1994; Gentont al., 2013).TCS typically start soon after the onset of MS andsually follow a cluster of MS (clonic-tonic-clonicequence) (supplementary figure 3.18); their diurnalistribution is similar to that of MS.

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bsences are usually infrequent, brief and mild,eported by only a tenth of patients. However,ideo-EEG recordings with appropriate assessment ofognition during GSWD identify mild absences inore than a third of patients (Panayiotopoulos et

l., 1989b), including phantom absences (supplemen-ary figure 3.19). Absences starting in childhood maye more severe or prolonged in the beginning, butecome milder and less frequent with age (see also

ransition of CAE to JME in the section on CAE [3.1]).

EG sectionackground. Within normal limits.

nterictal paroxysmal abnormalities.uring wakefulness

ypical generalized pattern:eneralized polyspike-wave discharges with anteriorredominance and more than three spikes in theolyspike component (supplementary figure 3.20B)an be asymmetric with lateralized onset, frequentlywitching sides in the same or sequential recordingssupplementary figure 3.21A and C; supplementarygure 3.22A and C); intra-discharge frequency is

ast but frequently unstable, showing irregular frag-entations (supplementary figure 3.23A). GSWD of

pparently posterior lead-in can occur (supplementarygure 3.21A) (Serafini et al., 2013).ther generalized patterns:(1) Classic (3-3.5-Hz) GSWD

supplementary figure 3.22A); this is most likely to asso-iate with brief and mild IoC (see absences below).(2) Fast pattern (>4-Hz) GSWD

supplementary figure 3.20A).ll generalized patterns tend to occur more in theorning than in the evening, are brief, and are acti-

ated by HV. Photoparoxysmal responses (PPRs) to IPSre elicited in >35% of patients with or without clinicalhotosensitivity.

Non-localizing) focal spikes, typically frontal orrontotemporal (supplementary figure 3.21D; sup-lementary figure 3.22B and D), but also posterior

supplementary figure 3.21B), unilateral or bilateral,ave been reported in up to 40% of patients (Serafinit al., 2013) and represent a major EEG factor for mis-iagnosis of JME as focal epilepsy, along with thesymmetric/lateralized GPSWD and the lateralizationf the myoclonic jerks.


uring sleepeneralized discharges become more frequent andriefer in slow sleep, with increased number of spikeser discharge (supplementary figure 3.20C; supple-entary figure 3.23C). They tend to occur in phases

f enhanced vigilance (cyclical alternating pattern; CAP A) and may initiate such phases in patients


E

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woFapi(

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ith poorly controlled seizures (Serafini et al., 2013),r during brief arousals (supplementary figure 3.24).ocal spikes tend to occur in phases of reducedlertness (CAP B) (supplementary figure 3.22D). Allatterns of generalized discharge attenuate or are

nhibited during rapid eye movement (REM) sleepsupplementary figure 3.25).

EG paroxysms that accompany ictal events.yoclonic seizures (MS). Brief, generalized high-

mplitude polyspike-wave discharges with multiplepikes (>5) in the polyspike component; symmetric orsymmetric (supplementary figure 3.17). Some patientsor bed partners) may report myoclonus during sleep,ut this is usually hypnagogic. Typically, MS occur fol-

owing arousals (supplementary figure 3.26).bsences. Brief, usually 3-5 sec, associated with theclassic” 3-4-Hz GSWD pattern; typically mild and sim-le. HV with breath counting may also reveal phantombsences (supplementary figure 3.19).eneralized convulsions. These may occur indepen-ently of MS or immediately follow a cluster of MS,howing the typical clonic-tonic-clonic sequence inhich discrete generalized bursts of polyspike-waverecede the pattern of generalized fast rhythms of theTCS (clonic-tonic-clonic sequence) (supplementarygure 3.18).

ecording protocolsasic levelTime: morning (first appointment of the day, if pos-

ible).Activation: HV: In untreated patients with JME, the

bove described interictal spike-wave discharges areery likely to occur during or immediately after HV,erformed with the patient sitting up with arms out-tretched or standing. HV can be performed twicer more, if needed. If no discharges occur and timellows, encourage light sleep and repeat HV after awak-ning, as above. MS may occur in a small number ofatients. Possible absences are typically expected to berief and mild. Therefore, the clinical basic assessmentf consciousness/responsiveness during the classic 3-.5-Hz or the faster (>4-Hz) GSW discharges is likely toe unremarkable (supplementary figure 3.20A); clinicaldvanced assessment is recommended with annota-ions by the physiologist on a digital or paper recordingsupplementary figure 3.19), if video-EEG is not

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