Typical Absence Seizures and Their Treatment
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Arch Dis Child 1999;81:351–355 351 Arch Dis Child: first published as 10.1136/adc.81.4.351 on 1 October 1999. Downloaded from CURRENT TOPIC Typical absence seizures and their treatment C P Panayiotopoulos Typical absences (previously known as petit there are inappropriate generalisations regard- mal) are generalised seizures that are distinc- ing their use in the treatment of other tively diVerent from any other type of epileptic epilepsies. fit.1 They are pharmacologically unique2–5 and demand special attention in their treatment.6 The prevalence of typical absences among Typical absence seizures children with epilepsies is about 10%, probably Typical absence seizures are defined according with a female preponderance.6 Typical ab- to clinical and electroencephalogram (EEG) 16 sences are easy to diagnose and treat. There- ictal and interictal expression. Clinically, the fore, it is alarming that 40% of children with hallmark of the absence is abrupt and brief typical absences were inappropriately treated impairment of consciousness, with interrup- with contraindicated drugs, such as car- tion of the ongoing activity, and usually unresponsiveness. The seizure lasts for a few to Department of Clinical bamazepine and vigabatrin, according to a 7 20 seconds and ends suddenly with resumption Neurophysiology and recent report from London, UK. Epilepsies, St Thomas’ The purpose of this paper is to oVer some of the pre-absence activity, as if had not been Hospital, London guidance to paediatricians regarding diagnosis interrupted. Although some absence seizures SE1 7EH, UK and management of typical absence seizures. can manifest with impairment of consciousness C P Panayiotopoulos This is also important because of the introduc- only, this is often combined with the following: tion of new antiepileptic drugs. These are + mild clonic jerks of the eyelids, corner of the Correspondence to: mouth, or other muscles Dr Panayiotopoulos. mainly tested in partial (focal) epilepsies and + atonic components leading to drooping of Girl born 1978 Video EEG 1992 Overbreathing with breath counting the head, slumping of the trunk, dropping of the arms, and relaxation of the grip Fp2-F4 + tonic muscular contraction causing head http://adc.bmj.com/ F4-C4 retropulsion or arching of the trunk C4-P4 + automatisms that are common and range from lip licking and swallowing to fumbling P4-O2 with clothes or aimless walking + autonomic components, such as pallor, and Fp1-F3 less frequently flushing, sweating, dilatation of pupils, and incontinence of urine.1 F3-C3 EEG is pathognomonic. In more than 90% C3-P3 of these children, absence seizures are docu- on September 23, 2021 by guest. Protected copyright. P3-O2 mented mainly during hyperventilation. Nor- 31 32Opens eyes–Unresponsive–Eyes to the right I am OK mal EEG results from a child suspected for absence seizures makes this diagnosis unlikely. 100 µV 1 sec The ictal EEG is characteristic, and usually has Girl born 1989 Video EEG 1998 Overbreathing regular and symmetrical generalised discharges of 3–4 Hz “spike and slow” wave complexes, Fp2-F4 and may also have multiple spike and slow wave complexes (fig 1).1 The background F4-C4 interictal EEG is usually normal. However, it C4-P4 should be stressed that asymmetries of the ictal P4-O2 discharge and focal abnormalities of mainly functional spikes are common.689 These Fp1-F3 should not be interpreted as evidence of focal F3-C3 epilepsy with secondary generalisation, which 7 C3-P3 could cause errors in treatment. P3-O2 Opens eyes–Stops OB–Unresponsive–Fumbling 200 µV 1 sec Epileptic syndromes manifested with typical absence seizures Figure 1 Top:part of a video EEG recording of patient 1 at age 14 years before adding The term typical absences does not refer to a small doses of lamotrigine to adequate doses of sodium valproate. Numbers annotate breath stereotype symptom but to a cluster of clinico- counting, which stopped after the onset of the discharge. Bottom: part of a video EEG recording of patient 2 at age 8 years before changing from syrup to tablets of sodium EEG manifestations, which might be syndrome valproate. related.610 352 Panayiotopoulos Four epileptic syndromes with typical ab- Absence seizures may also manifest with Arch Dis Child: first published as 10.1136/adc.81.4.351 on 1 October 1999. Downloaded from sences have been recognised by the Inter- subtle clinical manifestations during the typical national League Against Epilepsy, namely10: 3 Hz spike wave discharges. These are incon- childhood absence epilepsy, juvenile absence spicuous to the patient and imperceptible to epilepsy, juvenile myoclonic epilepsy, and myo- the observer (phantom absences). In these clonic absence epilepsy. The first three are cases, medical consultation is sought only after genetically determined idiopathic generalised a generalised tonic clonic seizure, probably epilepsies; that is, they occur in patients with long after the onset of absences.11 normal physical and mental states. Myoclonic Symptomatic typical absences mainly as a absence epilepsy is categorised among the result of frontal lesions are well established but cryptogenic/symptomatic generalised epilep- these are extremely rare.12 sies. Idiopathic refers to syndromes without an underlying cause other than a possible heredi- Biological basis tary predisposition.10 Symptomatic epilepsies Absences are provoked by an abnormal are the consequence of a known or suspected thalamo–cortical circuitry that activates abnor- disorder of the nervous system.10 Cryptogenic mal oscillatory rhythms, generating the gener- epilepsies are presumed symptomatic epileptic alised 3 Hz spike and wave discharges of typical 2–5 syndromes of an unknown, hidden, or occult absence seizures. The basic cellular mecha- aetiology.10 nisms involve low current T calcium channels; Childhood absence epilepsy (pyknolepsy) is ethosuximide exerts its anti-absence eVect by the archetypical epileptic syndrome of typical blocking these channels. GABA is the neurotransmitter that appears absence seizures with onset usually before the B to play the most prominent role. GABA age of 10 years and a peak at 5–6 years. B Absences are frequent (tens or hundreds each agonists, such as baclofen, aggravate and GABA antagonists suppress absences.2–5 day) manifesting with sudden, severe, and brief B Vigabatrin13 and tiagabine14 are GABA-ergic impairment of consciousness. As a rule, drugs, which interferes with degradation or absences are the only type of seizure. They re-uptake of GABA, and thus induces absences usually respond well to ethosuximide or and absence status epilepticus. sodium valproate and remit within 2–5 years from onset.610 DiVerential diagnosis Similarly, absences in juvenile absence epi- The diVerential diagnosis of typical absence lepsy are severe, frequent, and the main seizure seizures with severe impairment of conscious- type. However, onset is often later, after the age ness in children is relatively easy, although such of 10 years, and regularly generalised tonic seizures can be missed if they are mild, or in clonic seizures and random myoclonic jerks 610 babies, if they are not associated with myo- occur. Treatment may be life long. clonic components.6 Their brief duration with Conversely, in juvenile myoclonic epilepsy, abrupt onset and termination, their daily absences occur in only one third of the patients frequency, as well as their nearly invariable http://adc.bmj.com/ and they are usually mild without concurrent provocation with hyperventilation makes them 610 myoclonic jerks or automatisms. Juvenile one of the easiest types of seizures to diagnose. myoclonic epilepsy is a common idiopathic Automatisms, such as lip smacking or licking, generalised epilepsy characterised mainly by swallowing, fumbling with clothes, or aimless myoclonic jerks after awakening and general- walking, are common and should not be taken ised tonic clonic seizures. Myoclonic jerks start as evidence of complex partial (focal) seizures, in mid-teens but these may be predated by which require entirely diVerent management. absences. Juvenile myoclonic epilepsy is often In practical terms, a child suspected of having on September 23, 2021 by guest. Protected copyright. mild and responds well to treatment. However, typical absences should be asked to over- appropriate medication, usually with sodium breathe for three minutes while standing, valproate may be needed, even many decades counting his/her breaths, and with hands after cessation of seizures. extended in front of him/her. This will provoke Myoclonic absence epilepsy occurs mainly in an absence in as many as 90% of aVected indi- children with learning diYculties or other viduals. neurological deficits. Absences are associated Typical absence seizures of idiopathic gener- with rhythmic myoclonic jerks of the facial alised epilepsies are also easy to diVerentiate muscles, head, and limbs. The prognosis is from atypical absences that occur only in the poor.610 context of mainly severe symptomatic or cryp- Other epileptic syndromes can be associated togenic epilepsies of children with learning dif- with typical absences, such as eyelid myoclonia ficulties, who also suVer from frequent other with absences (Jeavons syndrome), perioral types of seizures such as atonic, tonic, and myoclonia with absences, stimulus sensitive myoclonic seizures.110 absence epilepsies, and others awaiting further The EEG should confirm the diagnosis of studies and confirmation.6 Of these syndromes, typical absence seizures in more