Epilepsy & Behavior 19 (2010) 100–104

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Review

Definition of the postictal state: When does it start and end?

Robert S. Fisher a,⁎, Jerome J. Engel Jr. b,c,d

a Department of Neurology and Neurological Science, Stanford University School of Medicine, Stanford, CA, USAb Department of Neurology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USAc Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USAd Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA

⁎ Corresponding author. Neurology, Room A343, SMedicine, 300 Pasteur Drive, Stanford, CA 94305-5235,

E-mail address: robert.fisher@stanford.edu (R.S. Fish

1525-5050/$ – see front matter © 2010 Elsevier Inc. Aldoi:10.1016/j.yebeh.2010.06.038

a b s t r a c t

a r t i c l e i n f o

Article history:Received 17 June 2010Accepted 17 June 2010Available online 7 August 2010

Keywords:EpilepsySeizureIctalInterictalPostictalElectroencephalographyEpileptiformSpikesSpike–waves

The postictal state is the abnormal condition occurring between the end of an epileptic seizure and return tobaseline condition. Applying this definition operationally can be difficult, especially for complex partialseizures, where cognitive and sensorimotor impairments merge imperceptibly into the postictal state. Manypatients are unaware of even having had a seizure. Electroencephalography sometimes helps to distinguishictal from postictal periods, but may demonstrate focal slowing both during and after a seizure. Epileptiformelectroencephalographic changes do not always correspond precisely to behavioral changes, especially withscalp recordings. The postictal state ends at the interictal state, but this too can be ambiguous. Interictal spikesand spike–waves can be associated with cognitive and behavioral impairments, suggesting that they mayrepresent fragments of ictal episodes. Except where boundaries are clear, it is better to describe a sequence ofbehaviors and electroencephalographic changes, without labeling arbitrary stages as being ictal or postictal.

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1. Introduction

A conceptual definition sets out a concept of themeaning of a term.Practical application, however, requires an operational definition,which provides a means to measure an observable condition or event.The conceptual definition of the postictal state is simple; however,formulating an operational definition is extremely difficult, if notimpossible. Conceptually, the postictal state is the abnormal conditionthat exists during the postictal period, which begins at the end of theepileptic seizure, or ictus, and ends with the return to baseline, which,when patients have recurrent seizures, is referred to as the interictalperiod. It is also implied that the abnormality of the postictal state issomehow a consequence of the ictus. Some postictal disturbancesduring the postictal period are due to systemic consequences of theepileptic seizure, for instance, headache, but these conditions are notconsidered in the following discussion.

An operational definition of the postictal state assumes ability tomeasure the postictal period, which is dependent on identifying theexact end of the ictus and the point when baseline is achieved.Unfortunately, in many, if not most, situations it is impossible to knowexactly when an epileptic seizure ends or, in some cases, whetherit occurred at all. Similarly, there is usually no way to definitively

determine exactly when function returns to baseline, and there isdebate about what constitutes the interictal period. Certain epilepti-form EEG events, such as spike-and-wave discharges occurring duringthis period, appear to be fragments of epileptic seizures, making theterms interictal spike–waves and interictal spikes oxymorons. Finally,not all intransient disturbances in brain function caused by an epilep-tic seizure, and rightfully considered postictal events, occur immedi-ately after the end of ictus; postictal psychosis follows a lucid intervalof hours or days. The following is a discussion of the pertinent issuesinvolved in analyzing features that characterize the many differentmanifestations of the postictal state, with the conclusion that apractical operational definition is possible with our current state ofknowledge only for a limited number of seizures with clear behavioraland electroencephalographic endpoints. Even in these ideal cases, thetermination of the postictal state can be ambiguous.

2. Beginning of the postictal state

The International League Against Epilepsy defines a seizure as “atransient occurrence of signs and/or symptoms due to abnormalexcessive or synchronous neuronal activity in the brain.” [1]. Seizuresmay result in a sudden alteration of sensation, motor activity,awareness, responsiveness,memory, or behavior.When this alterationis easily perceived by the patient or observed by others, and it has aclear finish, then the end of the seizure marks the beginning of thepostictal state. Unfortunately, this simple case is more the exception

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than the rule. Many seizures imperceptibly fade out. The EEG can behelpful in determining the state of the patient or, alternatively, mayprovide information discordant with behavioral observations. Whenpostictal psychosis develops a few days removed from the seizure, isthe intervening “lucid interval” part of the postictal state?

Howhard it is to distinguish ictal from postictal depends on the typeof seizure. A simple partial seizure preserves global awareness andmemory. Some simple partial seizures are associated with alteration ofresponsiveness, for example, impairment of speech when epileptiformactivity involves the language areas of brain. People usually retain theability to identify the startingandending timesof the sensationormotorphenomenon thatmark their simple partial seizures. Generalized tonic–clonic seizures similarly often demonstrate a behaviorally defined endwhen the clonic phase, characterized by rhythmic jerking, decelerates infrequency and stops. Although the final jerk is usually taken to initiatethe postictal period, epileptiform activity may persist beyond thebehavioral termination of some clonic seizures. In other generalizedtonic–clonic seizures, the clear-cut EEG transition of clonic dischargesinterspersedwith depression to postictal depression does not occur andthe ictal EEGmerely decreases in amplitude and eventually merges intoa low-voltage attenuated postictal pattern. Generalized tonic seizurespresent with head, trunk, or limb stiffening that is relatively easy tobracket in time. Atonic seizures are brief and marked fairly clearly bya period of decreased muscle tone. Offsets are less clear for absence,complex partial, and myoclonic seizures. Regrettably, this list consti-tutes the majority of seizures.

Ictal absence (previously called petit mal) seizures present less aproblem of delineation than of definition; however, these eventsusually are not associated with postictal behavioral impairment.During a typical absence seizure, a patientmay interrupt activities and“freeze.” Minor eye-fluttering or head-nodding automatisms arecommon. Concurrently recorded EEGs show bilateral frontocentrallymaximal runs of spike–waves (Fig. 1).

Recovery of function after an absence seizure is almost immediate;people are known to resume speaking in the middle of a sentence.Therefore, the end of the seizure can easily be determined for absence

Fig. 1. Electroencephalographic spike–waves. Is this likely to be interictal or ictal?

seizures that show a behavioral correlate. However, this abrupt returnof behavioral function does not always correlate with the exact timeof cessation of the EEG spike-and-wave discharge; it may precedeor follow the last spike-and-wave by a second or more. Anotherproblem derives from the continuously variable length of spike–wavedischarges. During a 1-second run of 3/second spike–waves, nobehavioral change is likely to be subjectively perceived or objectivelyobserved. In contrast, a 30-second run of spike–waves would likelyimpair behavior, responsiveness, and memory. Longer spike–waveruns are more likely to be associated with automatisms [2]. If wedesignate a 1-second-long spike–wave run as interictal and a 30-secondrun as ictal, how do we designate all corresponding absence seizureswith duration between these extremes? A binary categorizer such asinterictal/ictal does not apply to a continuous variable such as durationof spike–waves.

Myoclonic seizures involve sudden muscle jerks. Individual jerkslast less than a second, but often occur in clusters. The practicalproblem with defining the ictal state in myoclonic seizures is uncer-tainty as to whether to conjoin clusters of jerks into one seizure, as wedo with tonic–clonic seizures, or designate a series of individual ictal,postictal, and interictal sequences. No august body has profferedparameters to guide us in this dilemma.

Complex partial seizures provide the most problematic case fordistinguishing ictal frompostictal periods. Complexpartial seizures ofteninclude automatisms, such as lip smacking, fumbling, muttering stockphrases, undressing, wandering, and other automatic activities. Suchautomatisms are not unique to complex partial seizures, but can occur inother seizure types, for example, prolonged (atypical) absence seizures.However, the same automatic behavior can also take place during thepostictal state. Routine EEGs are not helpful in determining whetherautomatisms are ictal or postictal, given that ictal discharges occurring indeeper structures such as hippocampusmaynot be reflectedon the scalp[3]. It is possible that the commonly observed postictal cough or nosewipe actually does reflect termination of ictal discharges in the depth,although this has never been studied. In experimental animals, however,bilateral ictal discharges in limbic structures induced by kindling areassociated with analgesia [4], suggesting that the cough or nose wipeindicates that ictal analgesia has resolved.

EEGs recorded from implanted depth electrodes can sometimeshelp to define the offset of complex partial seizures originating inmesial or lateral temporal structures. Whether the initial ictal patternis hypersynchronous, low-voltage fast, or another variant [5], thebilateral ictal discharge that is associated with cognitive impairmenttakes on extremely variable patterns that can be asymmetric and oftenends in one region while continuing in another [6]. So, in addition tothe fact that it can be very difficult to determine exactly when the ictalEEG discharge ends and the postictal depression begins, given thatelectrodes cannot be implanted everywhere, delineation of the onsetof the postictal period is subject to sampling error.

With scalp recordings, seizures are often associated with rhythmicslowing in the theta (4–7/second) or delta (b3/second) frequencyrange. Rhythmic sharp wavesmay evolve into regional slowing (Fig. 2).Rhythmic slowing also is characteristic of the postictal state after apartial seizure. Focality of postictal slowing can mark the location of aseizure focus [7], but not the start of the postictal interval, as the slowingoften emerges imperceptibly from ictal slowing. Scalp EEGs, therefore,are of no help in defining the beginning of the postictal period.

It is not uncommon for patients to be completely unaware thatthey recently had a seizure. Blum et al. studied 31 consecutive patientsadmitted to an epilepsy monitoring unit with respect to seizureawareness [8]. Each was queried as to whether he or she recently hada seizure after a seizure and at other nonseizure times to discourageguessing. Approximately 30% were unaware of any of their seizures,including many that were complex partial or secondarily generalized.Similar findings were observed by Inoue and Mihara [9], with 24% of134 patients with complex partial seizures unaware of their seizures.

Fig. 2. EEG pattern at the start and end of a right temporal region complex partial seizure. Prominent 2/sec delta activity merges into less prominent postictal slowing.

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Unawareness wasmore likely with dominant hemisphere seizure foci.If an individual's awareness and memory are impaired during aseizure, that personmay not know that a seizure has occurred. In suchcircumstances, knowingwhether a confused individual is in a postictalstate may be impossible.

3. End of the postictal state

A seizure stops because of a variety of potentialmechanisms [5, 10],including, as examples, energy substrate depletion, receptor desen-sitization to excitatory neurotransmitters, depolarization block,desynchronization of neuronal networks, GABAergic and non-GABAergic inhibition, hyperpolarizing sodium–potassiumpumppoten-tials, and effects of inhibitory neuromodulators such as endogenousopiate receptor agonists, adenosine, endogenous cannabinoids, andneuropeptide Y (see also Löscher and Köhling [11]). These processeseach have different time courses of onset and duration, resulting in a

heterogeneous collection of factors inducing and maintaining alteredbehavioral states after a seizure. As each postictal mechanism runs itscourse, a different aspect of the postictal state progresses to resolution.Does the postictal state persist until every abnormal mechanismhas disappeared, and each behavioral function is back to baseline? Ifso, that sometimes can take many days or even longer.

The classic postictal Todd's paresis is said to last nomore than 24 to48 hours; however, there is no mechanistic reason for stating thisdefinitive duration. Occasionally, rapidly repeated focal seizures orfocal status can result in enduring deficits that have been attributed tolocalized structural damage; however, these can resolve over monthsto years. In this case, was this a transient functional disturbance,or did surviving neuronal networks eventually compensate for themissing brain tissue? A clear example of this is a patient who had focaloccipital status followed by hemianopsia that eventually resolvedover a period of a year [12]. An ictal PET clearly demonstratedhypermetabolism in the appropriate calcarine cortex, whereas a

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second PET scan 1 month later showed hypometabolism in the samearea (Figs. 3A,B). One year later, after the hemianopsia had resolved,the PET returned to normal (Fig. 3C).

Duration of the postictal state is of importance because it may signalwhen it is safe for a patient to return to usual activities. Few studieshave quantified the duration of the postictal state. Helmstaedter et al.presented words and pictures as patients recovered from complexpartial seizures in an epilepsy monitoring unit; recovery was nearlycompletewithin 1–2 hours [13]. Privitera et al. asked 26patients to reada standard test phrase after a complex partial seizure [14]; the meantime to read the phrase correctly was 322 seconds for left temporalseizures and 20 seconds for right temporal seizures.

Many patients, however, report postictal cognitive, mood, orenergy deficits lasting days. The quotes below describe examplesof prolonged postictal subjective experiences.

Quote 1: From a 22-year-old ski instructor:

For the following two days after that seizure, I just kinda feel outof it, although physically I continue with my daily duties. I cannot,for those two days, remember to call friends, to do things like Inormally would, and I just stay at home and perform things athome. The ideas don't come in as fast as they normally would todo things. Energy level during those two days is way down. Mymood is kind of just down and I kinda enjoy being by myself.

Quote 2: From a 39-year-old software programmer

Right after a seizure, I think I amperfectly normal, but the next day Irealize that I wasn't, and the next day I realize that I wasn't theprior day either. I may be stumbling around looking for things that Ishould know. The problem is there is no clean boundary between afugue from a seizure and a normal state long after a seizure.

Fig. 3. (A) Ictal PET during focal status epilepticus, showing left occipital hypermetab-olism. (B) Interictal PET 1 month after the episode of status demonstrates an occipitalregion of hypometabolism, including the left calcarine cortex (arrow), corresponding toa right homonymous hemianopsia. (C) By 1 year after the status, the interictal PET andthe visual deficit have normalized. Reproduced, with permission, from Ref. [12].

Postictal deficits recover over time, but at variable times andamounts. Detection of residual postictal deficits depends on the thor-oughness of testing.

The postictal state resolves into the interictal state. Interictalmeans “between seizures.” The termmakes little sense in relation to asingle seizure or in the absence of an impending subsequent seizure.Scalp-recorded EEGs can be normal between seizures, although theaccuracy of this statement is limited both by spatial and time-sampling problems. Longer-duration recordings or recordings withinvasive electrodes may detect previously unrecognized epileptiformEEG abnormalities. The majority of people with epilepsy demonstrateinterictal spikes or sharp waves in serially recorded EEGs [15].Interictal spikes usually are viewed as epiphenomena that mark theepileptogenic region. However, it is equally valid to view them asfragments of seizures, with potential impact on behavior. One study[16] analyzed incorrect and correct guesses about rectangles andwords flashed on a screen during periods of normal EEG activity ortimed to fall near an interictal sharp wave. Wrong answers were morelikely during or immediately after a sharp wave. Individual occipitalspike-and-wave discharges impair reaction time and accuracy to teststimuli presented in the appropriate area of the visual field, and thedeficit is related to the wave and not the spike [17–20]. If the spike is afragment of a seizure, is the slow wave postictal? Episodic cognitiveimpairment can be detected during times of brief spike–wave runs inpatients with absence seizures, provided that careful testing is done atthatmoment. The longer the spike–wave discharges, themore likely itis that cognitive function will be measurably impaired [2].

Since the time of Gibbs, Lennox, and Gibbs in 1936 [21], manyinvestigators have measured behavioral impairments associated withEEG epileptiform activity [22–44]. The degree of cognitive impairmentduring epileptiform EEG discharges is a function of the type, duration,and spatial distribution of discharges [45,46]. If interictal dischargesaffect cognitive function, are they really “interictal”? Examples ofapparently preserved behavior during a time of impressive epilepti-form EEG abnormalities also can be found [47]. Therefore, the EEG is ahelpful but imperfect tool to assist delineation of interictal, ictal, orpostictal time frames.

4. Conclusion

An operational definition of the postictal state comprises manyambiguities and requires assumptions about preservation of functionduring the interictal state that are not justified by experimental data.Table 1 summarizes the difficulties in defining the postictal state.

Before drawing conclusions regarding the definition of the postictalstate, it is necessary to askwhy such a definition is needed. There are atleast two reasons. One is in order to carry out research to understandthe basic mechanisms underlying postictal disturbances to prevent orreverse them, and the other is to identify disturbances in individualpatients that could compromise function or present a risk of injury.With respect to the first, operational definitions can be individuallyframed for the specific type of postictal disturbance under study. Withrespect to the second, it usually is better to describe than to categorize.Ideally, the terms ictal, postictal, and interictal should be applied only tocircumstances forwhich behavior and EEG clearly delineate the timeof

Table 1Difficulties in defining the postictal state.

1. When the ictal event ends often cannot be delineated.2. Many are unaware that they are having or had a seizure.3. Cognitive, emotional, and behavioral disability persists into the postictal state.4. Postictal disturbances are so variable that it can be impossible to determine

when they resolve.5. Epileptiform EEG events occurring during the interictal state are really fragmentsof seizures.

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seizure onset and termination. Phrases for “interictal spikes” or“interictal sharp waves” are ingrained in literature, but these entitiesshould be recognized as being associated with subtle clinical im-pairments that go beyond our usual meaning of interictal. Absenceseizures,with associated spike–wave runs, shouldnot be designated asinterictal or ictal, because behavioral concomitants are continuousfunctions of duration and individual variability. For practical clinicalpurposes, seizures and their aftermath can best be defined by carefulbehavioral observations. EEGs can provide important adjunctiveinformation, but epileptiform EEG activity, especially when recordedat the scalp,may neither correlatewith behavior, normark the end of aseizure.

The great philosopher and baseball player Yogi Berra commentedthat “It ain't over till it's over.” What he didn't say is that “it ain't soeasy knowing when that is.”

Acknowledgments

R.S.F. is supported by the James and Carrie Anderson EpilepsyChair, The Susan Horngren Research Fund, and the Littlefield Fund forEpilepsy Research. J.E. Jr. is supported by the Jonathan Sinay EndowedChair and Grants NS02808 and NS33310 from the National Institutesof Health.

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