The infant with seizures (excluding neonatal)

Symposium: EPILEPSY

The infant with seizures (excluding neonatal)

Definitions An epileptic seizure can be defined as a paroxysm in which there is quick emergence from and quick return to normal brain function, with resultant disruption of normal brain function, during which there is an increased firing rate in all, or most, neurones in a region or regions of the brain. Epileptic seizures may occur as the consequence of an acute event such as fever, acute central nervous system (CNS) infection, metabolic derangement such as hypoglycaemia or hypocalcaemia, toxic mechanisms (such as poisoning), hypoxia ischaemia, etc in which case they are described as ‘occasional’ seizures, or they may occur recurrently and spontaneously which is known as ‘epilepsy’.

Christopher DC Rittey

Abstract Seizures in infancy are common. Although there are a number of ­clearly defined epilepsy syndromes which begin or occur in infancy many infants cannot be readily classified into currently recognised epilepsy syndromes. This review discusses the clinical presentation, EEG findings, natural history and management of several recognisable epilepsy syndromes in infancy. Special syndromes including febrile convulsions and symptomatic seizures are discussed. There is also advice about investigation of seizures and syndromes in this population.

Classification The classification of the epilepsies is a minefield for the unwary. Early classifications, dating from the beginning of the last century, used the terms ‘grand mal’ and ‘petit mal’. In modern epilepsy practice, these terms are insufficiently precise to allow accurate description and diagnosis of seizures and in 1981 the International League Against Epilepsy (ILAE) adopted an internationally agreed system of classification of seizures (Commission on Classification and Terminology of the International League Against Epilepsy, 1981). This was updated in 2006, although the ILAE acknowledged that for the most part, the seizure types defined in the 1981 classification remained adequate. In 1989, the seizure classification was followed by a syndrome classification (Commission on Classification and Terminology of the International League Against Epilepsy, 1989). This is far too complex for routine everyday use. However, epilepsy syndromes can be broadly considered to be either focal or generalised and then either to be idiopathic (not due to any underlying brain disorder), symptomatic (consequent upon an underlying brain disorder) or cryptogenic (probably consequent upon an underlying brain disorder but that disorder cannot be defined or specified). Additionally, it is recognised that there are epilepsies in which it is not possible to determine whether they are focal or generalised, either because they have clear focal and generalised features or because they lack unequivocal focal or generalised features. Finally there are special syndromes in which seizures are situation related. Although there has been much discussion about a new classification scheme, these seizure and syndrome classifications remain current. The ILAE is still developing a more up-to-date system of classification.

Keywords benign familial/non-familial focal seizures; benign ­myoclonic epilepsy of infancy; dravet syndrome; epilepsy syndromes; febrile ­convulsions; HHE syndrome; migrating focal seizures; myoclonic-astatic epilepsy; West syndrome

Introduction Seizures are the most common neurological problem in childhood with a significant proportion of these either having their onset in infancy or occurring solely in infancy. Data about incidence of all seizures (whether epileptic or non-epileptic) in infancy are limited but epidemiological studies indicate that the highest incidence of epilepsy occurs in the first year of life and that this holds true even when neonatal seizures are excluded. Various studies have identified an incidence of between 95 and 190 per 100,000. The incidence of paroxysmal disorders other than epilepsy is considerably higher. Although specific data for infants do not exist, a large UK study found that 6.7% of children had experienced an episode of altered consciousness by 11 years of age compared with a cumulative incidence of epilepsy of 4.1 per 1000 by 11 years. It is important, therefore, for the clinician to be aware that seizures in infancy are not necessarily due to epilepsy and to be aware of the conditions that may present with loss of consciousness with or without other features. In infancy, febrile convulsions, breath-holding attacks, reflex asystolic syncope and faints without convulsion account for the majority of non-epileptic paroxysmal disorders but other rarer conditions – such as benign paroxysmal vertigo – may cause confusion. For a complete discussion of the differential diagnosis the reader is commended to read ‘Fits and Faints’ by Stephenson.

The epilepsies of infancy It should be noted that many of the epilepsies that occur in infancy do not easily fit into the syndromic classification defined by the ILAE and many new syndromes have been recognised. Focal epilepsies Idiopathic Benign familial/non-familial seizures Japanese authors described infants with focal seizures and good outcome and there have been subsequent non-Japanese patients described. The term ‘benign infantile seizures’ has been coined.

Christopher DC Rittey MB ChB FRCP FRCPCH is a Consultant Paediatric Neurologist at the Ryegate Children’s Centre, Sheffield, UK.

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Cryptogenic (or probably symptomatic) focal epilepsies in infancy are well recognised. Onset of seizures is usually before 4 months or after 8 months of age. There is some evidence that age of onset may be determined by the site of the focus – thus foci in areas of the cerebral cortex that mature early have earlier onset seizures. The causes of cryptogenic focal seizures in infancy are probably heterogeneous and, increasingly, advances in neuroimaging lead to positive aetiological diagnosis. Focal seizures in infancy frequently show motor and vegetative features including apnoea. Automatisms are well recognised and include chewing, swallowing, lip smacking and purposeless hand movements. In a large number of infants, the seizures may secondarily generalise. The pattern of seizures may change over time, possibly reflecting cortical maturation. The outcome of focal seizures in infancy is variable. In a study of 39 infants with focal epilepsy, 33 became seizure free and 27 had a normal developmental outcome. Positive prognostic factors included normal development before onset of epilepsy, absence of interictal EEG abnormalities, normal neuroimaging and absence of neonatal seizures.

Both familial and non-familial forms of this type of epilepsy have been described and the clinical features are very similar. Age of onset is usually from 3–20 months with a peak of onset at between 5 and 6 months in the non-familial form and between 4 and 7 months of age in the familial form. These infants are all neurodevelopmentally normal and make normal progress following remission of the epilepsy. Boys and girls are equally affected in the non-familial form but girls are more frequently affected in the familial form. Linkage has been defined to loci on chromosomes 19, 16 and 2. More recently, an intermediate form between benign familial neonatal seizures and benign familial infantile seizures has been defined. This has been called benign familial neonatalinfantile seizures (BFNIS) and has been shown to be due to a novel missense mutation in a sodium channel gene (SCN2A). Typically, the seizures occur in clusters with five to 10 seizures occurring daily for between 1 and 3 days. Seizures then remit but there may be a further cluster of seizures 1–3 months later. Seizures are focal and comprise motor arrest, impaired responsiveness, staring, head and eye deviation and mild clonic movements. There may be secondary generalisation and seizures may alternate from one side to another. Typically, seizures are brief, lasting between 30 seconds and 4 minutes. The electroencephalogram (EEG) is normal between seizures but ictal recordings demonstrate focal discharges that spread slowly or rapidly to surrounding areas or to the entire brain. Although seizure remission occurs with or without treatment, in practice the frequent seizures that occur usually necessitate treatment. A variety of drugs have been used including phenobarbital, carbamazepine, sodium valproate and zonisamide.

Migrating focal seizures This epilepsy syndrome was described in 1995 and since then a handful of additional cases have been reported. Previously normal infants present within the first 6 months of life with multifocal seizures. The fits are initially infrequent, focal and migratory becoming almost continuous and multifocal over a period of a few weeks. The seizures arise from either cerebral hemisphere and are either independently or sequentially multifocal. Infants lose all previously acquired skills and head growth slows or stops. In early studies the outcome was grim with 28% mortality and the majority of remaining survivors showing profound learning difficulties. Neuropathology in two cases who died showed bilateral hippocampal gliosis. A more recent study suggested that outcome was not invariably so poor.

Cryptogenic/symptomatic A large number of identifiable pathologies have been associated with focal seizures occurring in infancy (see Table 1). This is not an exhaustive list but highlights some of the most important causes.

Hemiconvulsion-hemiplegia epilepsy syndrome Hemiconvulsion-hemiplegia epilepsy (HHE) syndrome is a rare condition that was described in 1960 by Gastaut. This is now an extremely rare condition, possibly due to improved treatment of status epilepticus. The condition occurs in children aged 5 months to 4 years with a peak incidence within the first 2 years of life. This condition presents in a previously healthy child usually during a febrile illness. Typically, infants present with unilateral seizures that are usually prolonged, lasting hours or days if not treated effectively. Following this, the infant develops an ipsilateral hemiplegia that lasts for at least 7 days and which is permanent in 80%. Focal epilepsy follows in between 1 and 5 years in 80% of infants and focal cerebral atrophy and cystic necrosis is seen at follow-up. Although initial theories implicated a vascular mechanism, more recently it is believed that the condition is the direct result of the episode of status epilepticus itself.

Identifiable causes of focal seizures in infancy Neurocutaneous disorders

Vascular

Tuberous sclerosis Sturge-Weber syndrome Incontinentia pigmenti

Arteriovenous malformations Cavernous angiomata Tumours and hamartomas

Malformations Aygria-pachygyria Aicardi’s syndrome Hemimegalencephaly Focal cortical dysplasias (often difficult to identify on MRI) Hypothalamic hamartoma Chromosomal disorders Hypomelanosis of Ito

‘Damage’ Hypoxic ischaemic damage Meningitis Herpes encephalitis Metabolic Alpers disease Other mitochondrial diseases

Generalised epilepsies Idiopathic Benign myoclonic epilepsy in infancy This is a rare form of epilepsy which starts before 2 years of age, sometimes beginning as early as 4 months of age. The only

MRI, magnetic resonance imaging.

Table 1

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by Dr West in his own son. The syndrome is characterised by a triad comprising infantile spasms, a characteristic EEG abnormality (hypsarrhythmia) and cognitive impairment or regression. Infantile spasms are a specific seizure type that comprise abrupt, brief (0.5–2 seconds), bilateral (symmetrical or asymmetrical) tonic contractions of limb and trunk muscles. The spasms may be flexor, extensor or mixed and may be subtle and thus mistaken for other conditions such as ‘colic’. Typically, the spasms occur in clusters with between one and 30 clusters occurring per day and each cluster containing 20–100 spasms. Spasms often occur on arousal or during wakefulness and rarely occur during sleep. The typical interictal EEG pattern is characterised by high amplitude chaotic slow waves containing multifocal spikes. This is known as hypsarrhythmia. This abnormality usually first presents in sleep when it may be discontinuous (Figure 1a). Subsequently, the abnormality becomes apparent in the wake EEG as well (Figure 1b). In some patients, the pattern may be asymmetrical and this almost always indicates structural brain abnormalities. The ictal EEG accompaniment may be variable but in most patients comprises a high amplitude generalised slow wave followed by attenuation of EEG activity (electrodecremental event) and low amplitude fast activity. Developmental delay is present in 68–85% of cases before the onset of the spasms. In most infants, there is regression with a loss of interest in surroundings, which may be so profound that the infant appears blind. With remission of seizures there is usually improvement in development but most have permanent neurodevelopmental disabilities. The prognosis correlates most strongly with aetiology. Infants with cryptogenic or idiopathic West syndrome have a better outcome than those with an identified aetiology. Overall, between 15% and 30% of cryptogenic or idiopathic cases will have a good outcome whereas only 5–12% of all infants have normal cognitive and motor outcome. Approximately 5% of infants die and around 50–60% develop refractory epilepsies including Lennox-Gastaut syndrome or refractory focal epilepsies. There is no evidence that earlier treatment improves longterm prognosis. The aetiology of West syndrome is widely varied and includes: perinatal hypoxic ischaemic brain injury; CNS infection; tuberous sclerosis; cerebral malformations; chromosomal abnormalities such as Down’s syndrome; and inborn errors of metabolism such as branched chain aminoacidopathies, mitochondrial ­iseases, etc. Treatment of West syndrome has traditionally been with corticosteroids or adrenocorticotrophic hormone. More recently there has been interest in the use of vigabatrin, and other drugs such as sodium valproate, benzodiazepines, pyridoxine, topiramate, zonisamide and levetiracetam have been used with effect. Surgical treatment of localised lesions is increasingly recognised as effective in treating seizures. A recent UK multicentre study of treatment of infantile spasms compared hormonal treatment (prednisolone or tetracosactide) with vigabatrin. Out of 107 infants enrolled, five died and 101 reached the end of the study. The number of infants achieving absence of spasms was not significantly different between the two groups (41/55 for hormonal treatment, 39/51 for ­vigabatrin;

seizure type allowed in this epilepsy is myoclonic and infants are neurodevelopmentally normal. The seizures usually respond extremely well to sodium valproate and remission occurs between 6 months and 5 years of age, although 10–20% may experience generalised tonic-clonic seizures in later life. Prognosis is generally good but a small proportion of affected infants may develop mild cognitive or behavioural deficits. Myoclonic-astatic epilepsy (Doose syndrome) This epilepsy is now included as an idiopathic generalised syndrome in the diagnostic scheme suggested by Engel. There is considerable cross-over between the seizures type in this syndrome and other syndromes and, thus, distinction of this syndrome from other childhood epileptic encephalopathies may be difficult. Onset of the epilepsy is between 7 months and 6 years with a peak between 3 and 4 years. Boys are more commonly affected (2:1). Affected children are otherwise well although many have had febrile or afebrile generalised tonic-clonic seizures before the onset of the characteristic myoclonic-astatic seizures. The epilepsy is characterised by myoclonic-astatic seizures. These are seizures where a generalised myoclonia is followed by a loss of muscle tone (atonia). This results in the affected child dropping to the ground, often sustaining injury. Other seizure types that occur include absences, atonic, myoclonic and tonicclonic seizures. Non-convulsive status epilepticus is well recognised and affects up to one-third of patients. The interictal EEG is characterised by irregular generalised 2–3/second spike and wave discharges. The myoclonic seizures are associated with irregular spikes or polyspikes and the astatic seizure is associated with a generalised slow wave and reduction in electromyographic discharges, indicating a true atonic seizure. In myoclonic-astatic epilepsy neuroimaging is usually normal. Genetic mechanisms are strongly implicated and a family history of epilepsy or EEG abnormality is seen in 80% of cases. In some families described with generalised epilepsy with febrile seizure plus (GEFS+; a genetic form of epilepsy associated with SCN1A mutation), this type of epilepsy was one of the phenotypes encountered. The differential diagnosis of this epilepsy is between benign myoclonic epilepsy in infancy, Dravet syndrome and LennoxGastaut syndrome. Diagnostic difficulty may also occur with progressive myoclonus epilepsies. The outcome is variable in keeping with the fact that the syndrome may overlap with other types of epilepsy. Remission of seizures occurs in the majority of patients and, although many have a normal neurodevelopmental outcome, severe cognitive impairments and persistent refractory seizures are also described. Treatment is usually with sodium valproate although other drugs such as levetiracetam, lamotrigine and topiramate are useful in refractory cases. A ketogenic diet has also been reported to be useful. Cryptogenic/symptomatic West syndrome West syndrome is an age-related epileptic encephalopathy that has a peak incidence between 4 and 8 months and that usually occurs before 1 year of age. The disorder was first described

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a

b Electroencephalogram showing: a pseudo-periodic appearance in sleep; and b typical hypsarrhythmia in wakefulness. Figure 1

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Special syndromes Symptomatic seizures Symptomatic seizures in the infant can be provoked by a wide variety of factors. These include CNS infections such as ­eningitis (viral or bacterial), encephalitis, cerebral abscess or para-infectious encephalopathies such as Reye syndrome (now extremely rare). Other factors include metabolic disturbances (such as hypocalcaemia, hypoglycaemia, etc.) or metabolic encephalopathies due to renal or hepatic failure, hypertension or haemolyticuraemic syndrome. Head trauma, hypoxic ischaemic brain injury or cerebrovascular accidents can also cause seizures without requiring any intrinsic predisposition.

p = 0.82). Developmental outcome was assessed using the Vineland adaptive behaviour scales. In infants with cryptogenic West syndrome allocated to hormonal treatment there was significantly better developmental outcome than those allocated to treatment with vigabatrin. This difference was felt to be clinically important. The investigators are currently testing the hypothesis that better neurodevelopmental outcome may occur with combination of treatments. Both hormonal treatments and vigabatrin carry potential risks – with hormonal treatment the risks are of immunosuppression, gastric haemorrhage, cardiac insufficiency and death, while with vigabatrin the risk is of irreversible peripheral retinopathy. Thus, improved data about the benefits of these treatments is important in offering optimal treatment to patients.

Febrile convulsions Febrile convulsions are due to an age-related predisposition to seizures precipitated by fever without evidence of any acute or pre-existing cerebral abnormality. Age of onset is from 6 months to 5 years with a peak at around 18–22 months. Boys are slightly more frequently affected than girls. Prevalence is around 3% of children. The most common seizure type is generalised tonic-clonic and occurs in 80% of infants. Other seizure types including focal (with or without secondary generalisation), tonic and atonic are also recognised. The majority of febrile convulsions are simple (defined as duration less than 15 minutes and with no recurrence within the same febrile illness) but 30% of children experience complex febrile convulsions either lasting longer than 15 minutes, recurring twice or more in the same febrile illness or having focal features. All these complex features may occur in the same child. The risk of having a first febrile convulsion is approximately 28% if the child has two of the following risk factors: • first or second degree relative with febrile convulsions • neonatal discharge at 28 days or later • parental report of ‘slow’ development • day care attendance. Recurrence of febrile convulsions occurs in 30% of infants after a first febrile convulsion with half of those experiencing a second convulsion having at least one further convulsion. The only reliable indicators for recurrence appear to be early onset of first febrile convulsion and family history. The occurrence of a prolonged febrile convulsion does not increase the probability of recurrence but does increase risk that any recurrence will be prolonged. Children who have had febrile convulsions have a six times greater chance of developing epilepsy than the general population (i.e. 3% risk) with the risk being 1% after a simple febrile convulsion and 5–10% after a complex febrile convulsion. The risk factors for developing epilepsy are: • complex febrile convulsion, • abnormal development before onset of first febrile convulsion, • family history of epilepsy. The risk of epilepsy after a complex febrile seizure increases from 6% to 8% when a single risk factor is present to nearly 50% when all three factors are present. Investigation of children with febrile convulsion should be limited to investigation of the underlying cause of fever. Treatment of febrile convulsions requires control of seizures and treatment of the fever and, where necessary, the underlying cause. There is no evidence that use of antipyretic agents such as paracetamol reduces the likelihood of recurrence of febrile convulsions.

Dravet syndrome (Severe myoclonic epilepsy of infancy) Severe myoclonic epilepsy of infancy was first described by Dravet in 1978 and the syndrome now bears her name. Dravet syndrome is more common in boys than in girls (2:1) and accounts for up to 8% of epilepsies starting before 3 years of age. Dravet syndrome is a severe epilepsy characterised by the onset of prolonged generalised and focal clonic or tonic-clonic seizures in the first year of life with peak onset at 5 months. The earliest seizures tend to occur with fever and initially the infants may be thought to have febrile convulsions. However, the recurrent prolonged seizures and, later, the onset of other seizure types including myoclonias, atypical absences, alternating focal seizures and non-convulsive status epilepticus allows recognition of the syndrome. Progressive cognitive decline invariably occurs with developmental stagnation usually becoming apparent in the second year of life. Children with this epilepsy are usually left with severe learning and behaviour difficulties. Approximately 60% have ataxia and 20% have pyramidal signs. Seizures tend to remain refractory to medical treatment. The EEG in Dravet syndrome is usually normal at the onset but subsequently shows frequent generalised polyspike and wave discharges as well as focal and multifocal spikes. The background EEG deteriorates over time with increasing slow activity. Photosensitivity is seen in almost half of patients. Neuroimaging is usually normal although over time abnormalities such as hippocampal sclerosis may become apparent. Genetic factors have long been recognised to be important in Dravet syndrome and a family history of epilepsy or febrile convulsions occurs in approximately 25% of patients. Affected monozygotic twins have also been reported. Recently, the recognition that Dravet syndrome represents the most severe epilepsy syndrome in some families with GEFS+ led to the recognition that, in a significant proportion of children with Dravet syndrome, there is a mutation of the SCN1A sodium channel gene. Treatment of Dravet syndrome remains difficult and the seizures typically remain refractory to medical treatment. Stiripentol has been demonstrated to have remarkable efficacy as add-on therapy to sodium valproate and clobazam in a placebo controlled study. Other drugs such as topiramate, levetiracetam, zonisamide and ketogenic diet have also proved useful. Certain drugs including carbamazepine, lamotrigine, phenytoin and phenobarbital may worsen seizures.

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Other investigations A wide range of inborn errors of metabolism, neurometabolic and genetic conditions may present with epilepsy in infancy. ‘Routine screening’ is of little benefit but careful consideration of differential diagnosis should lead to effective use of metabolic studies. ◆

Investigations It is apparent from the description above that the possible causes of epilepsies arising in infancy are numerous and varied. Where specific epilepsy syndromes can be clearly recognised it is appropriate to investigate according to the recognised aetiologies. However, for many infants presenting with seizures it is not possible to immediately recognise a clear epilepsy syndrome and syndromic diagnosis may never be possible. It is important to bear in mind that epilepsy is ultimately a symptom of a derangement of cerebral function and, therefore, that all efforts should be directed towards understanding the aetiology in the individual child. Certain important diagnostic tests are worth considering in detail.

Further reading Capovilla G, et al. Benign partial epilepsy in infancy with complex partial seizures (Watanabe’s syndrome): 12 non-Japanese new cases. Brain Dev 1998; 20(2): 105–111. Chiron C, et al. Stiripentol in severe myoclonic epilepsy in infancy: a randomised placebo-controlled syndrome-dedicated trial. STICLO study group. Lancet 2000; 356: 1638–1642 [see comment]. Coppola G, et al. Migrating partial seizures in infancy: a malignant disorder with developmental arrest. Epilepsia 1995; 36(10): 1017–1024. Doose H, et al. Centrencephalic myoclonic-astatic petit mal. Clinical and genetic investigation. Neuropadiatrie 1970; 2(1): 59–78. Dravet C, et al. Severe myoclonic epilepsy in infancy: Dravet syndrome. Adv Neurol 2005; 95: 71–102. Dulac O, Plouin P, Jambaque I. Predicting favorable outcome in idiopathic West syndrome. Epilepsia 1993; 34(4): 747–756. Engel Jr. J. International League Against Epilepsy (ILAE). A proposed diagnostic scheme for people with epileptic seizures and with epilepsy: report of the ILAE Task Force on Classification and Terminology. Epilepsia 2001; 42: 796–803 [see comment]. Gastaut H, et al. H.H.E. syndrome; hemiconvulsions, hemiplegia, epilepsy. Epilepsia 1960; 1: 418–447. Hirtz DG, Camfield CS, Camfield PR. Febrile convulsions. In: Engel JJ, Pedley TA, eds. Epilepsy: a comprehensive textbook. Philadelphia: Lippincott-Raven, 1998, p. 2483–2488. Hrachovy RA, Frost Jr. JD. Infantile spasms. Cleve Clin J Med 1989; 56(Suppl. Pt 1): S10–6 discussion S40–42. Luna D, Dulac O, Plouin P. Ictal characteristics of cryptogenic partial epilepsies in infancy. Epilepsia 1989; 30(6): 827–832. Lux AL, et al. The United Kingdom Infantile Spasms Study (UKISS) comparing hormone treatment with vigabatrin on developmental and epilepsy outcomes to age 14 months: a multicentre randomised trial. Lancet Neurol 2005; 4: 712–717. Marsh E, et al. Migrating partial seizures in infancy: expanding the phenotype of a rare seizure syndrome. Epilepsia 2005; 46(4): 568–572. Mulley JC, et al. SCN1A mutations and epilepsy. Hum Mutat 2005; 25: 535–542. Okumura A, et al. Five-year follow-up of patients with partial epilepsies in infancy. Pediatr Neurol 2001; 24(4): 290–296. Roger J, Bureau M, Dravet C, Genton P, Tassinari CA, Wolf P, eds. Epileptic syndromes in infancy, childhood and adolescence. Eastleigh: John Libbey & Co, 2002. Ross EM, et al. Epilepsy in childhood: findings from the National Child Development Study. BMJ 1980; 280: 207–210. Specchio N, Vigevano F. The spectrum of benign infantile seizures. Epilepsy Res 2006; 70(Suppl. 1): S156–167. Stephenson JBP. Fits and faints, Cambridge: MacKeith Press, 1990. Watanabe K, et al. Benign complex partial epilepsies in infancy. Pediatr Neurol 1987; 3(4): 208–211. West WJ. On a peculiar form of infantile convulsions. Lancet 1841; 1: 724–725.

EEG The EEG is an extremely important investigation in infants with epilepsy. However, as with any investigation, it is important to understand both its strengths and its limitations. EEG is invaluable in the following: • Seizure classification – frequently it is extremely difficult or even impossible to accurately identify seizure types from clinical description, particularly when the clinical information is incomplete. The combination of video and EEG can be crucial in determining seizure type and even, when a typical attack is recorded, in determining whether an attack has an epileptic basis or not. • Syndromic diagnosis – the classification of epilepsy syndromes is dependent on both clinical and EEG characteristics and accurate diagnosis is, therefore, dependent on EEG. However, there are significant limitations to the EEG. • More than 10% of children will have non-specific EEG abnormalities without having epilepsy. Up to 4% of children will have ‘epileptiform’ abnormalities. • Children with pre-existing neurological abnormalities have a higher incidence of ‘epileptiform’ abnormalities on EEG • Frequency of seizures is not proportional to the frequency of EEG discharges EEG is a clinical investigation and the quality of the information derived from an EEG is directly related to the quality of information provided to the neurophysiologist and the clarity of the question asked of the investigation. Optimal information from EEG comes from effective communication between the requesting clinician and the neurophysiologist. Magnetic resonance imaging Magnetic resonance imaging (MRI) is now the imaging modality of choice in epilepsy. The National Institute for Clinical Excellence in Clinical Guideline 20 – Epilepsy in adults and children – has recommended that MRI is particularly important in those: • who develop epilepsy before the age of 2 years or in ­adulthood • who have any suggestion of a focal onset on history, examination or EEG (unless clear evidence of benign focal epilepsy) • in whom seizures continue in spite of first-line medication. Effectively this guidance means that the vast majority of infants presenting with epilepsy will require MRI. Subtle abnormalities may not be evident on MRI performed under 18 months of age and in many children repeat imaging will be required after 2 years of age.

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Practice points

• The prognosis of epilepsies beginning in infancy is variable but many have poor neurodevelopmental outcome • There are multiple causes of seizure in infancy and careful clinical assessment and, where possible, syndromic diagnosis is important in directing investigation

• Seizures in infancy may be non-epileptic as well as epileptic • Current systems of classification are inadequate to define the epilepsies of infancy • Both seizures and epilepsies may be focal, generalised or undetermined

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