Brain, Vol. 125, No. 2, 436-437,
February 1, 2002
© 2002 Oxford University Press
Book Review |
LIMBIC SEIZURES IN CHILDREN
Llanvapley, Abergavenny, UK
LIMBIC SEIZURES IN CHILDREN.
By C. Munari, G. Avanzini, A. Beaumanoir and L. Mira.2001. Eastleigh: John Libbey.
Price £39. Pp. 258. ISBN 0-86196-595-7..
The concept of limbic seizures was introduced by Broca in the late 19th century, though Willis had already used the term ‘limbus’, a fringe or border, in an anatomical treatise 200 years earlier. In addition to being the borderland of Hell, Limbo, the ablative of the Latin ‘limbus’, is defined as any unsatisfactory place of consignment or oblivion; an uncertain or intermediate state; a prison. When considering limbic seizures, such descriptions seem apposite, not only in anatomical and functional terms, but also from the viewpoint of seizure semiology and particularly in relation to the possibility that very unpleasant subjective sensations may occur. The editors and their authors have undertaken a difficult task, and are to be commended for the production of a multi-faceted, well-referenced book, which follows a colloquium aimed at outlining the specific expression of epilepsies involving the limbic structures in children and establishing a consensus on the evidence relevant to the clinical management of these epilepsies.
Precise information on seizures originating in the limbic system is rather sparse in the paediatric age range, particularly in very young children and infants. Therefore, it is, perhaps, only to be expected that some chapters produce data that are largely confined to patients in their second decades or to adults. The contributions devoted more or less completely to children include those on pathology; clinical expressions of seizures, usually with simultaneous EEG findings, and sometimes video recording; EEG; medical therapy; surgical therapy; and a consideration of whether a benign limbic epilepsy exists in childhood. It is disappointing that the chapters on neurovegetative manifestations, language and speech disturbances, mesiotemporal seizures and symptoms differentiating ‘temporal’ from ‘frontal’ cortical partial seizures relate mainly to adults. However, their inclusion in this text adds emphasis to the paucity of information on these subjects in younger age groups and the need to devote more attention to the special circumstances of childhood.
An extensive historical review concludes by highlighting questions relevant to the overall theme of age-specificity. These address the uncertainties about the semiology and the timing of initial events deemed responsible for lesions in Ammon’s horn, and of the evolution of such pathology. The authors of the chapter on anatomy believe that the limbic system defines only an anatomical entity and not functional properties, though those who wrote the contribution on functional organization of the limbic system would no doubt dispute this. Both these chapters are written in styles which are intelligible to the non-specialist in these fields. In particular, the diagrams explaining the anatomical groups within the limbic system are clear and informative. The importance of timings in neurogenesis and neural migration is emphasized. For example, neurones of layer 1 of the neocortex and limbic cortex are developed between 5 and 8 weeks of gestation (maximally 
6–7 weeks); and, the latest to develop, dentate granule cells of the hippocampus are not formed until 15–40 weeks of gestation (maximally 19–32 weeks). In addition, there are three different processes involved in migration: ‘inside-out’ (cells which migrate first are overtaken to more distal sites by those migrating later) in the neocortex, parahippocampal region, CA1, CA2 and CA3; ‘outside-in’ (cells migrating first remain the outer layer) in the granular layer of the dentate nucleus; and, supragranular–infragranular in the dentate gyrus. Clearly, there is considerable potential for disruption of these sequences if adverse events occur during foetal life. Pathophysiological consequences would then seem likely. The important possibility that function in the limbic system might alter with age, particularly in the very young child, is not addressed. On the other hand, a contribution on experimental seizures in young rats found that expression and propagation of hippocampal seizures are age-dependent; and gives evidence to suggest that intrahippocampal cortical heterotopias can contribute to generalization of hippocampal focal paroxysmal activity.
The reviews of clinical material are particularly relevant to the practising child neurologist. It can be very difficult to know whether or not changes in posture, movement patterns, behaviour and autonomic phenomena constitute seizures, especially in the very young and the handicapped, who are unable to verbalize unpleasant or other sensations. When the authors specified the age ranges of their groups and examined infants or pre-school children separately, the seizure semiologies were not consistent throughout childhood, though complete agreement between the groups of authors was not reached. When patients were defined by age, automatisms were considered common in pre-school children, but when identified by the presence of a tumour, automatisms were reported as rare or minimal in the same age range. In two contributions, seizures similar in characteristics to infantile spasms, but confirmed by EEG as arising in the limbic system, were noted in very young children. On the whole, phenomena observed in or reported by children over the age of 6 years were comparable with those experienced by adults. Although most authors reported the findings in relatively small cohorts, in all, there is a lot of information on the many forms that limbic seizures can take. A well-argued chapter considers the connection between febrile seizures and limbic epilepsy and tends to favour the presence of a predisposing event or circumstance for the complex febrile seizure, which is followed by hippocampal pathology. Interesting discussions on the pathology of hippocampal lesions that are identified in children emphasize that mesial temporal sclerosis is a very rare finding, and is virtually unknown before the age of 4 years. This again underlines the need to consider any disorder of childhood as an evolving process, in line with continued maturation of anatomical and functional aspects.
The chapter on memory disturbances in early hippocampal dysfunction is fascinating. However, it would have been helpful to have been given the ages of the subjects described. This is followed by a very good and very critical review of the literature on psychic alterations in temporal lobe seizures in children, which concludes that, although neuropsychological problems are common in children with epilepsy, these are not specifically related to temporal lobe epilepsy, but are more in keeping with the overall cognitive status. The information on perceptual and intellectual disturbances is somewhat sparse and relates almost entirely to a surgical series and its outcome. Of the chapters on investigation, the one on ictal EEG looks at a surgical sample and emphasizes that it is important to differentiate limbic seizures from those arising from the temporal cortex. Rhythmic spikes or rhythmic slow wave discharges, previously considered to be typical of temporal lobe seizures, were seen on only three of 57 occasions, whereas, characteristically, ictal activity consisted of well-localized fast activity or well-localized flattening. Previous information on ictal SPECT in children of <4 years of age is almost completely lacking. The usefulness of this investigation, particularly when co-registered with MRI, is well emphasized. The main messages of the chapter on MRI are that hippocampal abnormalities are often just one feature of more extensive developmental anomalies, and, that hippocampal signal abnormalities on MRI do not always mean hippocampal sclerosis. It was once again underlined that hippocampal sclerosis is much rarer in children than in adults.
There are numerous interesting reports on the various expressions of limbic seizures in children, but the second aim of the book, a review of medical and surgical therapies, is very brief. However, such data can be found elsewhere without too much difficulty. In fact the chapter on surgery contains a wealth of information on electroclinical correlations that is at least as useful as any other in the book.
I have enjoyed reading Limbic seizures in children. I can thoroughly recommend it to all those who work in paediatric epilepsy. Those whose remit is the neurology of adults, and who wish to enlarge the breadth of their knowledge of the early histories and development of their patients with epilepsy, will find much of relevance and interest in this text. It is an essential source of information on a group of conditions which are usually poorly defined. It should act as a spur to the further investigation of this very challenging area of epilepsy.
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