161

EPILEPSY OCTET Epileptic seizures and syndromes LENNART GRAM

Need for classification The hallmark of epilepsy is recurrent epileptic seizures. However, there are many types of epileptic seizures, some of which may easily be mistaken for symptoms of other diseases--eg, hypoglycaemia, Stokes-Adams attacks, narcolepsy, and psychiatric disorders. A detailed description and classification of epileptic seizures is therefore very useful. Moreover, choice of antiepileptic treatment will depend on seizure type.

Epileptic seizures An international classification of epileptic seizures appeared in 1981 (see S. Shorvon, this series).1 Like epileptic syndromes (see below), seizures are classified into two main groups-generalised and partial or focal seizures. Descriptions of the most important seizure types are shown in tables I-IV. Epilepsy may manifest itself in the form of more than one seizure type in the same patient. In addition, seizures of one type-eg, generalised tonic-clonic convulsions-may be easy to treat in some patients but very difficult to control in others. These observations suggest (a) that one type of seizure may be the expression of various "kinds" of epilepsy and (b) that some epilepsies may involve several types of seizures. Consequently, a classification of epilepsy that encompasses more than seizure type might be worthwhile.

hereditary predisposition; and cryptogenic, presumed to be symptomatic but the aetiology is not known. Classification of epileptic syndromes is not a static process and new syndromes are delineated every year. Some of these syndromes are very specific whereas others represent broad concepts. Syndromes may overlap. TABLE I-GENERALISED EPILEPTIC SEIZURES Absences (petit mal) Age group Duration

Symptoms Ictal EEG Special features

Children and juveniles Few-30 seconds Sudden loss of consciousness accompanied by staring and blinking; immediate regain of consciousness Bilateral regular 3 (2-4) Hz spike-waves Long absences may be accompanied by

automatisms, lip smacking, chewing, fiddling, fumbling, &c Myoclonic seizures Age group Symptoms

Children and juveniles 1-5 seconds Brief jerks in arms or legs

Ictal EEG

Polyspike-waves, spike-waves, or sharp and

Special features

slow waves Often occur in series

Duration

Atonic seizures (astatic)

Age group Duration

Symptoms

Infants and children Few seconds Sudden loss of muscle tone causing head injuries (fall)

severe

Ictal EEG

Epileptic syndromes An international classification of epileptic syndromes, approved by the International League Against Epilepsy, appeared in 19852 and in revised form in 1989.3 An epileptic syndrome is defmed as an epileptic disorder characterised by a cluster of signs and symptoms occurring together. These features include type(s) of seizure(s), aetiology, anatomy, precipitating factors, age of onset, severity, chronicity, possible diurnal and circadian cycling of seizures, and prognosis. Table v gives an outline of the 1985 classification and lists some of the most important syndromes. Syndromes are designated localisation-related (partial) or generalised; localisation-related is now used instead of focal or partial because the term focal implies a well-defined constant epileptic focus, which is not always the case. In some childhood epilepsies the focus may shift from side to side and even the site of onset may change. Three expressions are used with regard to the aetiology of syndromessymptomatic, believed to be the consequence of a known or suspected disorder of the central nervous system; idiopathic, which implies no underlying cause other than a possible

Polyspike-waves, flattening, or low-voltage fast activity Generalised tonic- clonic seizures (grand mal) Age group Any age Duration

Symptoms

Ictal EEG Special features

1-3 minutes Initial cry (sometimes); loss of muscle tone (fall); respiratory arrest; cyanosis; tonic convulsions; clonic convulsions; relaxation followed by deep sleep Often obscured by muscle artifacts Possible tongue biting and urinary incontinence

Advantages of a syndrome diagnosis If the classification of epilepsy is restricted to seizure type, the result is knowledge/experience about which drug should be preferred for treatment but this is almost the only information that such a classification provides. Moreover, guidance about choice of drug may not always be correct (see below). ADDRESS: Dianalund Epilepsy Denmark (Dr L Gram, MD, Dr Med

Hospital, DK-4293 Dianalund, Sci).

162

TABLE II-PARTIAL EPILEPTIC SEIZURES

deprivation-which preventive measures.

may

consequently

be avoided

by

One of the immediate questions raised by the family when child presents with seizures is the likely chronicity of the condition and, ultimately, the prognosis. Detailed information can be provided for several epileptic syndromes. Finally, a syndrome diagnosis may offer guidance about the preferred type of medical treatmentthe choice of antiepileptic therapy may depend not only on the type of seizure but also on the syndrome. I will illustrate the advantages of a correct syndrome diagnosis by reviewing two epileptic syndromes and emphasise the additional information such a diagnosis provides compared with a seizure-type diagnosis. a

epilepsy (benign childhood epilepsy with centrotemporal spikes) Rolandic epilepsy is a well-defined epileptic syndrome4,s

Rolandic TABLE III-SECONDARILY GENERALISED SEIZURES

If a syndrome diagnosis can be made it will often provide far more information—eg, about age of onset, aetiology, seizure type, factors, chronicity, prognosis, and choice of treatment. Since many of the epileptic syndromes are age related, the age of onset of seizures may provide a clue to the correct syndrome diagnosis but seldom by itself provides additional information. Some syndromes have a specific aetiology whereas others are less specific. Thus a single syndrome may comprise two subtypes, a cryptogenic and a symptomatic form-eg, West syndrome (infantile spasms) and LennoxGastaut syndrome (myoclonic astatic epilepsy). As I mentioned above, some syndromes encompass more than one type of seizure, some of which may be subtle. Frequently, only detailed questioning of the patient will reveal their existence. Compared with the classic seizure types, some seizures may be "atypical" and therefore confound the differential diagnosis-eg, frontal lobe seizures. Epileptic syndromes may be the result of specific

seizure-provoking

seizure-provoking factors-eg, photosensitivity

or

sleep

TABLE IV-FEATURES COMMON TO SIMPLE AND COMPLEX PARTIAL SEIZURES Frontal lobe seizures Usual pattern

Symptoms

Parietal lobe seizures Usual pattern

Symptoms

Symptoms

Adversive movements of the head; prominent manifestations (especially in the legs) Frequency: several times daily. Duration: seconds. Despite impairment of consciousness very little postictal confusion

1 Localisation-related (focal, partial syndromes) 1.1 Idiopathic Rolandic epilepsy (benign childhood epilepsy with centrotemporal

Simple partial + secondary generalisation Sensory and/or motor symptoms (Jacksonian march); infrequently painful sensations Complex partial ± secondary generalisation Epigastric rising sensation; olfactory and gustatory hallucinations; deja vu, jamais vu; oral and other primitive automatisms; visual hallucinations; postictal confusion

Occipital lobe seizures Usual pattern

Symptoms

epilepsy Juvenile myoclonic epilepsy was first described many years ag06 and has subsequently been reviewed.7 Seizures start around puberty. The aetiology is idiopathic with a TABLE V-CLASSIFICATION OF IMPORTANT EPILEPTIC SYNDROMES

Temporal lobe seizuress Usual pattern

Juvenile myoclonic

Simple partial, complex partial, + secondary generalisation motor

Special features

that starts between the ages of 3 and 13. This condition is 3-4 times more common than absences (pyknoleptic petit mal). The child has simple partial seizures, with sensory and motor symptoms originating from the throat, and there is often secondary generalisation. Seizures occur almost exclusively at night, after a few hours sleep. The strange noises emanating from the throat and the inability to speak may be very frightening for the child and the parents. The electroencephalogram (EEG) shows a high-voltage centrotemporal spike focus which may shift from side to side. Despite the clearcut partial seizures and pronounced focal EEG changes, the aetiology of this syndrome is idiopathic with a genetic predisposition. Consequently, in typical cases there is no need for neuroradiological examinations, which would otherwise be indicated by the focal features of the epilepsy. In addition, despite the strict focal nature of the seizures, the response to antiepileptic treatment is very successful. Treatment can be discontinued after a few years’ freedom from seizures and in some children seizures are so infrequent that treatment is not indicated. A diagnosis of this syndrome therefore offers important information about therapy and outcome.

Simple partial ± secondary generalisation Unformed simple visual phenomena (sparks, flashes, phosphenes)

spikes) Occipital epilepsy 2 Generalised syndromes 2.1 Idiopathic Childhood absence epilepsy (pyknoleptic petit mal) Juvenile absence epilepsy 2.2 Cryptogenic or symptomatic Infantile spasms (West syndrome) Myoclonic astatic epilepsy (Lennox-Gastaut syndrome) Epilepsy with myoclonic absences 3 Syndromes undetermined whether focal or generalised 3.1 With both generalised and focal seizures Neonatal seizures Epilepsy with continuous spike-waves during sleep

163

pronounced hereditary element; the gene for this syndrome may be on chromosome 6.8 Juvenile myoclonic epilepsy is a common syndrome, accounting for about 5% of all cases of epilepsy. There are three seizure types-myoclonic jerks, occurring in the morning; generalised tonic-clonic convulsions, also developing in the morning or at least before noon; and absences, which develop less frequently. Myoclonic jerks may be present years before the onset of convulsions; unless questioned specifically, patients very seldom describe the jerks, although they may greatly interfere with everyday life. Sleep deprivation and alcohol are well-established seizure-provoking factors in epilepsy in general but in this syndrome may provoke seizures to such an extent that it may be necessary for the patient to abstain completely and to adopt a rigid lifestyle with regard to sleep. An EEG obtained at the correct time-ie, in the morning after sleep deprivation-may show characteristic abnormalities in the form of polyspike-wave paroxysms. If the EEG is recorded at other times the trace may be entirely normal. Characteristic EEG changes are sometimes found in family members without seizures. Juvenile myoclonic epilepsy is often mistaken for "grand mal" epilepsy, for which the drugs most frequently used are phenytoin or carbamazepine. However, when this seizure type is caused by juvenile myoclonic epilepsy both drugs are almost ineffective and they do not influence the myoclonic jerks or the absences. The drug of choice for this syndrome is sodium valproate.9 Despite complete seizure control for many years, withdrawal of treatment is often associated with recurrence, so extended periods of treatment are called for.

To detect this syndrome any young person who presents with convulsions should be questioned about diurnal fluctuations of seizures and myoclonic jerks. If relevant, an EEG should be obtained in the morning after sleep

deprivation. The syndrome of juvenile myoclonic epilepsy therefore has implications with regard to diagnostic measures, seizure preventing behaviour, choice of treatment, and duration of therapy. REFERENCES 1. Commission

on Classification and Terminology of the International League Against Epilepsy. Proposal for revised clinical and electroencephalographic classification of epileptic seizures. Epilepsia

1981; 22: 489-501. 2. Commission on Classification and

Terminology of the Intematonal League Against Epilepsy. Proposal for classification of epilepsies and epileptic syndromes. Epilepsia 1985; 26: 268-78. 3. Commission on Classification and Terminology of the International League Against Epilepsy. Proposal for revised classification of epilepsies and epileptic syndromes. Epilepsia 1989; 30: 389-99. 4. Lombroso CT. Sylvian seizures and mid-temporal spike foci in children. Arch Neurol 1967; 17: 52-59. 5. Beaussart M. Benign epilepsy of children with rolandic (centro-temporal) paroxysmal foci. Epilepsia 1972; 13: 795-811. 6. Janz D, Christian W. Impulsiv-petit mal. Dtsch Z Nervenheilk 1957; 176: 346-86.

Janz D. Epilepsy with impulsive petit mal (juvenile myoclonic epilepsy). Acta Neurol Scand 1985; 72: 449-59. 8. Greenberg DA, Delgado-Escueta AV, Widelitg H, et al. JME may be linked to the HLA locus on human chromosome 6. Cytogenet Cell Genet 1987; 47: 623 (abstr). 9. Covanis A, Gupta AK, Jeavons PM. Sodium valproate: monotherapy and polytherapy. Epilepsia 1983; 23: 693-720. 7.

Pseudoseizures: seizures that

are not

epilepsy

TIM BETTS Pseudoseizure is an unfortunate term since it is both pejorative and wrong. A non-epileptic seizure is still a seizure, and it is usually not the patient’s fault if the doctor’s diagnosis of the cause of seizure behaviour is erroneous. Non-epileptic attack disorder (NEAD) is a better term and not accusatory. Doctors have always recognised the need to distinguish between epilepsy and non-epilepsy-the ancients claimed to be quite good at it1-and an association between strong emotions and sudden seizures has long been acknowledged. Modem technology may help to distinguish epileptic from non-epileptic attacks but will not help us to decide what to do with the patient whose seizures are not

epileptic.2 NEAD (and even pseudo status epilepticus) are more than many doctors realise and both conditions are economically and socially important. Perhaps 20% of patients referred to specialist centres for treatment of intractable epilepsy have non-epileptic attacks and have had much previous unnecessary investigation and anticonvulsant treatment. Since the diagnosis of epilepsy is often no more than an informed guess, all of us who work in this area have had the blush making experience of treating a patient’s epilepsy unquestioningly for years only to discover eventually that the seizures were something else. Conversely, a confident diagnosis of pseudoseizures may common

have to be revised to epilepsy—eg, bizarre behaviour in frontal lobe seizures is easy to misdiagnose. Often NEAD and epilepsy co-exist, which makes recognition difficult.3

Classification

My working classification of the different causes of NEAD is shown in the table. In a 20-year experience of NEAD I have encountered all the listed organic causes, often more than once, epilepsy having been diagnosed by doctors who did not know, for instance, that incontinence and injury can occur in faints, as can twitching, and that unconsciousness during a faint will be prolonged if the patient is kept propped up rather than allowed to lie flat. The various forms of acute anxiety are also easy to mistake for epilepsy, especially those involving changes in the perception of reality, or carpopedal spasm or unconsciousness.4 NEAD that are emotionally based but not related to misdignosed psychiatric illness take several distinct forms.

Department of Psychiatry, University of Birmingham, and Neuropsychiatry Clinic, Aston University, Birmingham B47ET, UK (Dr T. Betts, FRCPsych).

ADDRESS

Epileptic seizures and syndromes.

161 EPILEPSY OCTET Epileptic seizures and syndromes LENNART GRAM Need for classification The hallmark of epilepsy is recurrent epileptic seizures. H...
381KB Sizes 0 Downloads 0 Views