Download - EEG and Epilepsy Alving

EEG and EEG and epilepsyepilepsyPanumPanum InstituteInstitute 31.5.200731.5.2007

Jørgen Alving, MDDanish Epilepsy Center

DK-4293 Dianalund

EEG and EEG and epilepsyepilepsy”Epilepsy is thename of occasional, sudden, excessive rapid and localdischarges of greymatter”

John HughlingsJackson, 1873

EEG and EEG and epilepsyepilepsy

What does the clinician want from theneurophysiologist?They want him/her to prove or disprovethe diagnosis of epilepsy!


”We will neither prove nor disprove thatour vessels carry nuclear weaponswhile visiting your harbours”

Standard explanation given by the US Navy to the Danish Government during the Cold War


But we can say whether or not there areepileptiform abnormalities in the EEGThe presence of these will give important clues as to which type ofepilepsy is most likely (classification)

EEG: EEG: whatwhat is is ””epileptiformepileptiform””? ?

”Epileptiform” EEG abnormalitiesfocal or/and generalised paroxysmalabberations from the background EEG whichare strongly correlated to epilepsyThey are rarely seen in persons withoutepilepsy or other neurological diseases


“Epileptiform” EEG3 Hz spike-waves3½-6 Hz poly-spike-waves2 Hz spike-waves + 10 Hz trains during sleepHypsarrhytmiaAnterior temporal sharp-wave focus withprefrontal spreadCentro-midttemporal sharp-waves + 4-5 Hz Repetitive focal trains of spikes

GeneralisedGeneralised spikespike--wavewave paroxysmparoxysm((childhoodchildhood absences)absences)

GeneralisedGeneralised polyspikepolyspike--wavewaveparoxysmparoxysm (juvenile (juvenile myoclonicmyoclonic

epilepsyepilepsy))

GeneralisedGeneralised 2 Hz 2 Hz spikespike--wavewaveparoxysmparoxysm (Lennox(Lennox--Gastaut)Gastaut)

RhythmicRhythmic 10 Hz 10 Hz traintrain in in sleepsleep(Lennox(Lennox--Gastaut)Gastaut)

HypsarrhytmiaHypsarrhytmia (infantile (infantile spasmsspasms))

Mesial temporal Mesial temporal epilepsyepilepsy

Mesial temporal Mesial temporal epilepsyepilepsy ((ictalictal start)start)

””RolandicRolandic”” focusfocus

Repetitive Repetitive ictalictal traintrain ofof spikesspikes


A pitfall: not all paroxysmal EEG activityis epileptiform!Beware of the so-called ”normal variant patterns”

EEG: normal variantsEEG: normal variants

What are normal variants?Apparently paroxysmal EEG events, i.e. alterations with an abrupt and steeplyrising appearance, often with a tendency to rhythmicity

EEG: normal variantsEEG: normal variants

But they are not infrequently seen in normal people and have a lowcorrelation to epilepsyThey are often misinterpreted as providing evidence of epilepsy


“Normal variants” I (wake/drowsy)6 and 14 Hz positive spikes6 Hz spike-waveswicket spikesrhythmic theta in drowsiness(“psychomotor variant”)SREDA (Sublinical RhythmicElectrographic Discharges in Adults)

14 Hz positive spikes (14 Hz positive spikes (CommonCommonAverageAverage Reference)Reference)

14 Hz positive spikes14 Hz positive spikes

Formerly ascribed to variousneurological and psychiatricdisturbances, including”thalamic/hypothalamic” epilepsy, etc.Now considered a normal variant –mostly in children and young adultsLocation posttemporal & parietal, synchronous/asynchronous

6 Hz 6 Hz spikespike--wavewave ””FOLDFOLD”” ((CommonCommonAverageAverage Reference)Reference)

6 Hz 6 Hz spikespike--wavewave ””FOLDFOLD”” (Double (Double BananaBanana))

6 Hz 6 Hz spikespike--wavewave ””FOLDFOLD””(Transversal)(Transversal)

6 Hz 6 Hz spikespike--wavewave

Two variants:”WHAM” = wake, high, anterior, male”FOLD” = female, occipital, low, drowsyLower amplitude & higher wave-frequency than in generaliseredepileptic paroxysmsDisappear in sleep

GeneralisedGeneralised spikespike--wavewaveparoxysmparoxysm ((sleepsleep stage 2)stage 2)

WicketWicket spikes (spikes (CommonCommon AverageAverageReference)Reference)

WicketWicket rhythmrhythm ((CommonCommonAverageAverage Reference)Reference)

WicketWicket spikesspikes

Seen in 0.5 – 1 % of normal peopleUsually after age 30 yearsGradual or more abrupt ”pop-up” from background activityLocation temporal, asynchronous/synchronous, in drowsinessNo aftercoming slow wave or otherdisturbance of background activity

Mesial temporal Mesial temporal epilepsyepilepsy

””RhythmicRhythmic temporal temporal thetatheta in in drowsinessdrowsiness””

””RhythmicRhythmic temporal temporal thetatheta in in drowsinessdrowsiness””

Occurrence: 0.5 – 2 % of normal adultsMostly in younger peopleMostly midtemporalSynchronous or asynchronousDisappears in sleep

Mesial temporal Mesial temporal epilepsyepilepsy ((ictalictal start)start)

SREDA = SREDA = SublinicalSublinical RhythmicRhythmicElectrographicElectrographic DischargesDischarges in in

AdultsAdults

SREDASREDA

Occurrence: not given – but mostly in persons above age 50 yrsDuration of trains from 20 sec. to several min. (usually 40-80 sec.)Mostly parieto-posttemporalFocal or asynchonous occurrenceConstant frequency during whole train


“Normal variants” II (sleep)hypnagogoc hypersynchrony“spikey” vertex-sharp-waves“mitten pattern” K complexespositive sharp transients in sleep(POSTs)

HypnagogocHypnagogoc hypersynchronyhypersynchrony

””SpikeySpikey”” VV--wavewave ((CommonCommonAverageAverage Reference)Reference)

””SpikeySpikey”” VV--wavewave (transversal)(transversal)

””Mitten Mitten patternpattern”” K K complexcomplex

””Mitten KMitten K”” and and paroxysmalparoxysmalactivityactivity

Gradual transition: spindles -> mitten K complexes -> generalised polyspike-wave paroxysms (E. Niedermeyer)

GeneralisedGeneralised polyspikepolyspike--wavewaveparoxysmparoxysm

POSTsPOSTs ((CommonCommon AverageAverageReference)Reference)

POSTsPOSTs (Double (Double BananaBanana))


”Epileptiform” EEG in epilepsyEpileptiform interictal standard EEGFirst recording 50 %Repeated with relevant provocations 85 %No further yield after 4.-5. recording

• (Salinsky, Kanter & Dashieff, Epilepsia 1987)


“Epileptiform” standard EEG in epilepsy1. recording 38 %2. recording 49 %4. recording 66 %6. recording 77 %7. recording no more!

Doppelbauer et al, Acta Neurol Scand 1993;87:345-52

EEG and EEG and epilepsyepilepsy“Epileptiform” standard EEG in epilepsyTime since latest seizure< 24 hours 53 %24 hours - 1 week 42 %later 36 %

NB only standard EEG (20 min., wake + hyperventilation & photic stimulation)

Doppelbauer et al, Acta Neurol Scand 1993;87:345-52

Standard EEG and Standard EEG and epilepsyepilepsy

Sensitivity of 1. EEG (”positive”EEG/patients with epilepsy): 35-50 %Specificity of 1. EEG (”negative”EEG/”very healthy” persons): Adults 99,5 % Children 98 %

EEG EEG afterafter firstfirst afebrileafebrile seizureseizure??

Epileptiform EEG -> 2-3 times increased recurrence riskOften seizures before the ”indexseizure” , making the case more complexSpecific epilepsy syndromes may bediagnosed at this early stage

EEG EEG afterafter firstfirst afebrileafebrile seizureseizure??

Subtle seizures (absences and myoclonias) can be recorded on theEEG (simultaneous video)Provoking factors (e g photosensitivity) can be demonstrated


EEG AND EPILEPSY: WHICH PROVOCATION IS PREFERRABLE?

Seizure/syndrome Best methodAbsence epilepsies hyperventilationJuvenile myoclonic epilepsy photic stimulation,

sleep/awakening, sleep deprivation


EEG AND EPILEPSY: WHICH PROVOCATION IS PREFERRABLE?

Seizure/syndrome Best methodComplex focal seizures SleepRolandic epilepsyTemporal lobe epilepsyCSWS


Sleep: how much is needed?Focal and generalised paroxysms in general: ca. 30 min. (sleep stage 2-3) CSWS: for quantitation, a whole-night EEG with EOG is needed (paroxysmal activitydecreases later in the night and especiallyduring REM sleep)


What to expect from a sleep EEG if first EEG is negative (children)?Negative 1. EEG: 44 % (243/552)Positive sleep EEG: 34 % (61/177)Total positive EEGs: 67 % (370/552)

Carpay et al, Epilepsia 1997;38:595-599


What to expect from a sleep EEG if first EEG is negative (children + adults)?Negative 1. EEG: 57 % (171/300)Positive sleep EEG: 35 % (55/158)Total positive EEGs: 61 % (184/300)

King et al. Lancet 1998;352:1007-1011

EEG: EEG: strengthsstrengths

EEG is a noninvasive ”window to the brain”, and gives as regards temporal resolution an unsurpassed image of normal and abnormalcortical activityIn the definition of epileptic syndromes, EEG is essentialOften difficult to differentiate between focaland generalised epilepsies without EEG

EEG: EEG: strengthsstrengths

Subtle seizures like absences og ”eyelidmyoclonias” only detectable by EEGEEG is the best method of investigationin neonatal seizures

EEG: EEG: weaknessesweaknesses

Unspecific and non-diagnostic EEG alterations in about 10 % of normal personsMore or less epileptiform EEG in 2 to 4 % of children and 0.5 to 1 % of adultswithout epilepsy

EEG: EEG: weaknessesweaknesses

Epileptiform EEG are frequent in patients with neurological and psychiatric disordersOften weak or no correlation betweenthe amount of EEG paroxysmal activityand the clinical conditionThis correlation varies very muchbetween syndromes

CorrelationCorrelation EEG EEG -- seizuresseizures

Examples:Rolandic and benign occipital epilepsy: oftenmassive (multi)focal pathology in patients with very few seizures and a good prognosis– and despite drug tratmentAbsence epilepsies: optimal treatmentrequires eradication of generalisedparoxysmal activity

CorrelationCorrelation EEG EEG -- seizuresseizures

Epilepsy is essentially a clinical diagnosis, based upon observed seizure phenomenaBut the EEG has provided insight into someobscure and enigmatic conditions dominatedby massive paroxysmal activity with no orminimal clinical seizures, e.g. Landau-Kleffner´s syndrome and Continuous Spike-Waves during slow Sleep (CSWS)

CSWSCSWS

Problems in Problems in ””routineroutine”” interictalinterictalEEGEEG

Limited recording time (30 - 60 min.)Limited number of electrodesLimited part of cortex in proximity to electrodes

EEG EEG -- seizuresseizures and timeand time

EEG EEG –– spatialspatial aspectsaspects

Intensive Intensive neurodiagnosticneurodiagnosticmonitoring (INDM)monitoring (INDM)

Aim: to record EEG during seizuresRecording time: until a technically and clinically satisfactory recording of sufficient number of episodes in question are obtained, i.e. highly variable in durationNot necessarily a long-time monitoring

Intensive Intensive neurodiagnosticneurodiagnosticmonitoring (INDM)monitoring (INDM)

IndicationsDifferential diagnosisSeizure classificationSeizure frequencyFocus localization (epilepsy surgery)Clinical correlates of paroxysmal EEGSeizure-provoking factors, e.g. reflex epilepsy

INDM INDM –– contributionscontributions to to diagnosisdiagnosis

Retrospective study 199 adults (in-ptt.)Recording time 72 hours (median)Episodes recorded in 167 (84 %)Clarified diagnosis: 151 (76 %) -hereofPNES 91 (45 %)Epilepsy 37 (19 %)

Lobello et al., Epilepsy & Behavior 2006

INDM INDM –– contributionscontributions to to diagnosisdiagnosis

143 (88 %) of episodes on day 1 or 2No difference between PNES and epilepticseizures in time to first eventNo difference in alleged seizure frequencybefore INDM and time to first eventPositive correlation between epilepticseizures and: epileptiform EEG & abnormalMRI

Lobello et al., Epilepsy & Behavior 2006

What the EEG cannot doWhat the EEG cannot do

Prove the diagnosis of epilepsyExclude the diagnosis of epilepsyMonitor anti-epileptic treatmentEvaluate the severity or frequency of seizuresDecide when to stop AED treatment in seizure-free patientsEvaluate developmental and neuropsycho-logical problems

What the EEG can doWhat the EEG can do

Support clinical suspicion of epilepsy (if other cerebral diseases can be excluded)Diagnose (or exclude) epileptic syndromes(e.g. childhood absences, Rolandic epilepsy)Detect photosensitivityDetect non-convulsive status epilepticus

What the EEG can doWhat the EEG can do

Monitor status epilepticus in anaestetisedpatientsMonitor treatment of absence seizures and photosensitive epilepsyIn some cases predict risk of relapse after stopping AED Help localizing the epileptogenic zone (epilepsy surgery)

OtherOther utilisationsutilisations ofof thethe EEG EEG signalssignals

Dipole or multiple source modelling for focus localisationDC-EEG for detection of ictal alterationsNon-linear analysis for prediction of seizures

DipoleDipole sourcesource modellingmodelling for focus for focus localisationlocalisation

Multiple Multiple sourcesource modellingmodelling for for focus focus localisationlocalisation

MUSIC (Multiple Source Classification)Correlates well with ictal SPECT in focus localisation (temporal lobeepilepsy)

Beniczky et al, Neuroreport 2006;17:1283-87

InterictalAwake

InterictalAsleep

InterictalBeforeSeizure

DCDC--EEG EEG shiftsshifts

DC shifts in ictal recordings (temporal lobeepilepsy) is seen together with beginning ofictal rhythmic discharges (also in intracranialstudies)May reduce the need for invasive pre-surgicalEEG recordings?

• Vanhatalo et al, Neurology2003;60:1098-1104

DCDC--EEG EEG shiftsshifts

NonNon--linearlinear analysisanalysis for for predictionpredictionofof seizuresseizures

May be able to predict seizures up to four hours before occurringAlso feasible in scalp EEG recordings

Lehnertz et al, J Clin Neurophysiol2007(2):147-53; Drury, Smith & Savit, ExpNeurol. 2003 Nov;184 Suppl 1:S9-18.

EEG EEG –– patternspatterns and interpretationand interpretation

“To some people, the first movement of Beethoven´s Eroica Symphony symbolises Napoleon, to others Hitler and to others again Mussolini. To me, it is just Allegro con brio.”

Arturo Toscanini