Benign childhood seizure susceptibility syndromes

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					                                                                                  Chapter 9

Benign childhood seizure susceptibility syndromes

MICHAEL KOUTROUMANIDIS

St Thomas’ Hospital, London



The most important milestone in recent epileptology has been the recognition of epileptic
syndromes and diseases, most of which are well defined and easy to diagnose1. The benign
childhood partial seizure susceptibility syndromes (BCSSS)2-4,4 exemplify the importance
of the syndromic classification of epilepsies. They are common, comprising about one-
quarter of all epilepsies with onset under 13−15 years of age and have an excellent
prognosis2. BCSSS4 are classified under ‘age and localisation related idiopathic
epilepsies’5: the epileptic seizures and the EEG abnormalities are focal (localisation-
related), only occur in children (age-related), and physical, mental and laboratory
examinations other than EEG are normal (idiopathic). Occasional abnormal neuroimaging
findings have no bearing on the excellent prognosis, and their presence does not preclude
the diagnosis of BCSSS6. The combination of a normal child with infrequent seizures and
an EEG with disproportionately severe focal epileptogenic activity is highly suggestive of
BCSSS4. The tendency in the UK not to request an EEG after a first seizure7 (which is now
formally discouraged8) may result in underestimation of the prevalence of BCSSS, as
10−40% of children with BCSSS may have only a single seizure2,4.

It is currently recognised that there are two major syndromes of BCSSS: Rolandic epilepsy
(benign childhood epilepsy with centrotemporal spikes) and Panayiotopoulos syndrome
(susceptibility to early onset benign childhood seizures with prominent autonomic ictal
features and occipital and extra-occipital spikes or normal EEG)9,10. Childhood epilepsy
with occipital paroxysms of Gastaut11, is another recognised syndrome but this is rare, of
undefined boundaries and of uncertain prognosis2,12. There are also other rare and less well
defined syndromes of BCSSS4 such as BCSS with occipital photosensitivity13,14,13,14 BCSS
with fronto-parietal-temporal spikes and affective symptomatology15, BCSS with frontal16,
midline, or parietal spikes2,17.2,4

Rolandic epilepsy (benign childhood epilepsy with centrotemporal spikes)

This is a well known genetic18 form and features in all relevant textbooks. Prevalence is
around 15% of children with afebrile seizures and has distinctive clinical manifestations
and EEG abnormalities.

    •   A typical case is of a boy 7−10 years old found by his parents at night salivating
        and gurgling, attempting unsuccessfully to speak, and apparently conscious.
        Unilateral motor seizures, mainly of face and hand, may ensue progressing to a
        secondary generalised tonic-clonic seizure.
    •   Also, typical is a case of a child at the same age that during daytime has brief hemi-
        facial twitching (mouth more than eye) with hypersalivation and speech arrest ‘I
        wanted to say that I could not speak’.

The inter-ictal EEG shows frequent, mainly high amplitude sharp and slow-wave
complexes, unilateral or independently bilateral over the Rolandic and sylvian areas. These
so-called centrotemporal spikes (though rarely of maximum amplitude over the temporal
electrodes) are exaggerated by sleep and may also be elicited by somatosensory stimuli.
There is often bipolar topography of their electrical field showing focal negativity over the
centrosylvian and simultaneous positivity over the frontal regions. Between 10 and 20% of
these children may show sharp and slow-wave complexes in other cortical locations2.

The benign character of this syndrome has been demonstrated in long follow-up studies.
Most children have 1−10 infrequent seizures but 10% may have many seizures. Rolandic
seizures resolve within 1−3 years of onset and no later than 16 years of age. The risk for
‘epilepsy’ later in life (1−2%) is lower than of febrile convulsions2, and may include
atypical evolution into Landau-Kleffner syndrome, episodes of status epilepticus or atypical
mixed phenotypes19. Despite the excellent prognosis with regard to seizure remission,
behavioural problems and cognitive dysfunction may sometimes develop during the course
of this condition20-22 but these are usually transient and reversible2. The extent and severity
of such behavioural/cognitive changes need confirmation in truly representative
populations of children with Rolandic seizures.

Panayiotopoulos syndrome

This common and benign childhood epileptic syndrome has only recently attracted
interest9,10,23-25, and is detailed in a monograph26. The following are examples of typical
cases9:
    • A five-year-old girl woke up at night and vomited. Initially she was able to speak,
         but within minutes her eyes turned to the right and she gradually became
         unresponsive. A generalised convulsion occurred one hour later. She was well next
         morning.
    • A four-year-old boy became pale and restless, and felt sick and vomited while at
         school. He was able to answer simple questions. His eyes then turned upwards and
         to the left. He became flaccid and unresponsive and vomited repeatedly over the
         next three hours. He then had a convulsion. He was normal next morning.
    • A five-year-old girl complained of feeling sick after a race at school. Over the next
         half hour she vomited and became disoriented and incontinent of urine and faeces.
         Subsequently, her eyes turned to one side; she became limp, pale, and unresponsive
         for five hours. She then gradually recovered and was well after a few hours of
         sleep.

These are striking histories suggesting grave cerebral insults. However, they are all typical
of a common and benign epilepsy syndrome first described by Panayiotopoulos28,29 and
recently recognised by the International League Against Epilepsy Task Force on
Classification30.

Panayiotopoulos syndrome can be best defined as idiopathic susceptibility to early onset
benign childhood seizures with electroencephalograhic occipital or extra occipital spikes,
and manifests mainly with autonomic seizures. It probably affects about 13% of children of
3−6 years old with one or more non-febrile seizures (peak age 4−5 years), and 6% of the
age group 1−15.

Autonomic symptoms and signs (mainly vomiting) occur from the onset in 80% of seizures,
with half of them lasting for more than 30 minutes to hours, thus amounting to autonomic
status epilepticus. Two-thirds of the seizures occur during nocturnal sleep or brief daytime
naps. In a typical daytime seizure the child looks pale, complains, ‘I want to be sick’, and
vomits. If in sleep, the child wakes up with similar complaints or is found vomiting,
confused, or unresponsive. Vomiting occurs in three-quarters of seizures. Other autonomic
manifestations may occur either concurrently with vomiting or later in the course of the
seizure, and include pallor, mydriasis, cardiorespiratory, gastrointestinal and
thermoregulatory alterations, incontinence, and hypersalivation. In at least a fifth of the
seizures the child becomes unresponsive, pale, and flaccid (ictal syncope) either before
convulsing or in isolation. Behavioural disturbances, headache, or various non-painful
cephalic sensations are common particularly at onset. More conventional manifestations of
seizures often ensue: the child becomes confused or unresponsive, eyes may deviate to one
side (in 60%) or the patient may stare. Half of the seizures end with hemi or generalised
convulsions. Other, less frequent ictal features include speech arrest, hemifacial spasms,
visual hallucinations and oropharyngolaryngeal movements, suggesting a maturation related
continuum with Rolandic epilepsy4.

Diagnosis may be easily missed − mild and brief ictal autonomic symptoms in the presence
of clear consciousness would suggest trivial non-epileptic conditions such as atypical
migraine, gastroenteritis or syncope, while prolonged and severe attacks may simulate life-
threatening insults such as encephalitis, for which many of these children are treated.
Characteristically, even after the most severe seizures and status, the child is normal after a
few hours of sleep − this is both reassuring and diagnostic.

Electroencephalography, which should be done after a first non-febrile seizure, is
confirmatory. This usually shows multifocal spikes at various locations. Though occipital
spikes predominate they are neither specific nor a prerequisite for the diagnosis. Normal
recordings may occur in 25% of children and should prompt an EEG during sleep to
activate the spikes; on strong clinical suspicion a sleep EEG should be performed from the
beginning. A useful rule of thumb is that Panayiotopoulos syndrome should be considered if
a normal child with a single or a few seizures has an EEG with multifocal spikes31.

Panayiotopoulos syndrome is remarkably benign. Remission usually occurs within two
years from onset. One-third of these children have a single seizure, and only 5−10% have
more than ten seizures that may be very frequent sometimes but the outcome is still
favourable. Lengthy seizures do not appear to result in residual deficits or have adverse
prognostic significance. One-fifth of children with this syndrome may develop other types
of infrequent, usually Rolandic seizures, but these also remit before the age of 16 years. It
follows that treatment with antiepileptic drugs (AEDs), mainly carbamazepine, is usually
unnecessary but may be considered in children with multiple seizures. The decision should
also take into account a likely traumatising parental experience as in febrile convulsions.
Appropriate advice by the family doctor is expected to shape parental attitude and prevent
chronic anxiety.

Idiopathic childhood occipital epilepsy (Gastaut)

This is a rare and less well defined form of BCSSS5,11,32, with a probable prevalence of
around 2% of BPSSS2. Misdiagnosis as migraine is common12.

    •   A typical case is a 10-year-old child with frequent daily seizures of elementary
        visual hallucinations ‘many small balls of various brilliant colours’ lasting for
        10−30 seconds. If longer, these were often followed by severe migrainous
        headache. Infrequently the visual symptoms could progress to hemiconvulsions and
        impairment of consciousness. Occasional episodes of complete blindness that start
        and end suddenly with or without other preceding visual symptoms could occur.
        He was erroneously diagnosed as basilar or migraine with visual aura or
        migralepsy.
This condition is characterised by visual seizures that consist mainly of elementary visual
hallucinations, blindness, or both. The former are the commonest, characteristic and
frequently the only ictal symptoms. They are usually frequent and diurnal often lasting for
seconds, and consist of multiple, bright coloured, small circular spots, circles, or balls12 that
are entirely different from the features encountered in the visual aura of the classical
migraine2. Elementary visual hallucinations may progress and co-exist with other occipital
symptoms such as sensory illusions of ocular movements and ocular pain, tonic deviation
of the eyes, eyelid fluttering, or repetitive eye closures2,11,32. Ictal blindness, appearing ab
initio or, less commonly, after other occipital seizure manifestations, usually lasts for 3−5
minutes. Ictal headache, mainly orbital, may occur. Consciousness is intact during the
visual symptoms, but progression may occur and the seizures may infrequently terminate
with hemi- or generalised convulsions. Complex visual hallucinations, visual illusions, and
other symptoms from more anterior ictal spreading are rare.

Post-ictal headache, sometimes indistinguishable from migraine headache, occurs in half of
the patients2,11. Most of the patients are misdiagnosed as having migraine with aura, basilar
migraine, acephalgic migraine, or migralepsy simply because physicians are not properly
informed of differential diagnostic criteria2,12.

On EEG occipital paroxysms frequently occur but they are not a prerequisite for diagnosis.
MRI is mandatory because symptomatic cases with similar seizures are common. As
opposed to Rolandic and Panayiotopoulos syndromes treatment here is needed and the drug
of choice is carbamazepine. Prognosis is uncertain but most patients remit after the age of
18 years.

Pathophysiology and a unified concept of benign childhood seizure susceptibility
syndromes

Panayiotopoulos is responsible for this concept, according to which all these conditions
represent age related phenotypes of a common, genetically determined, mild and reversible,
functional derangement of the maturational process that regulates cortical excitability4. This
remains clinically silent in more than 90% of these children who only have EEG sharp and
slow waves with an age related-localisation. In the remaining 10%, infrequent partial
seizures occur with age related topography of onset and propagation, and therefore different
constellations of ictal symptoms and signs. It is possible that a few of these children, with
or without seizures, also have usually minor and reversible neuropsychological symptoms,
whereas in less than 1% this derangement of the brain maturation process may be derailed
resulting in a more aggressive condition of seizures, neuropsychological manifestations and
EEG abnormalities of various combinations and various degree of severity including
atypical or mixed forms, Landau-Kleffner syndrome and continuous spike and slow wave
during sleep19.

Treatment

There is no consensus on whether to treat these children with AEDs2. After a second
documented seizure most physicians recommend treatment lasting 1−3 years, mainly with
carbamazepine, but treatment may not be needed, at least in typical cases33. Aggravation of
benign childhood epilepsy with centrotemporal spikes has been reported to occur
occasionally with carbamazepine and probably with phenobarbitone during periods
coinciding with spontaneous worsening of seizures34.
Conclusions

All agree that BCSSS or, at least, their major representatives have a benign course with
remission within either a few years of onset or no later than 16 years of age. Unfortunately,
current textbooks and even journals of paediatrics, medicine and neurology pay scant
attention to these syndromes, often considering childhood seizures under the heading
‘epilepsy’ without considering aetiology and prognosis. There is still a social stigma
attached to the diagnosis of ‘epilepsy’ and these children are frequently excluded from
activities of their peers with sometimes severe psychological consequences. BCSSS, like
febrile convulsions, are age related, show genetic predisposition, may be manifested by a
single seizure only, remit within a few years of onset, and may or may not require but a
short course of antiepileptic medication. The risk of recurrent seizures in adult life (1−2%)
is less than for febrile convulsions (4%). Therefore, in analogy with the term ‘febrile
convulsions’, the term ‘benign childhood seizure susceptibility syndromes (BCSSS)’ is
preferable to ‘epilepsy’, and should be used instead.


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