Annotation Hippocampal plasticity in children with epilepsy

Three main types of pathological change are recognized in the hippocampus in children with epilepsy: neuronal loss and gliosis, mossy ®bre sprouting and dentate dispersion. In mesial temporal sclerosis (MTS) there is increasing evidence that cell loss in speci®c sub®elds of the hippocampus may be related to age at precipitating injury. The relationship of febrile or complicated seizures to MTS remains unclear. Mossy ®bre sprouting is a manifestation of reorganization and plasticity of the neuronal processes of the dentate granule cells but the stimulus for mossy ®bre sprouting remains unclear despite insights from both experimental work and studies in human epilepsy. Two main patterns of structural changes in the dentate gyrus have been described in human epilepsy: generalized dispersion with granule cell bodies identi®ed in the molecular layer or separation of the dentate gyrus into two distinct laminae. There appears to be no consensus on the criteria for de®ning dentate dispersion. There is continuing controversy over the in ̄uence of seizure type and history on hippocampal damage. It is increasingly recognized that the brain is capable of continuing plasticity for many years after birth. In the hippocampus this leads to multiple patterns of pathology. While these processes have been considered damaging and a cause of further epilepsy they may also represent adaptive change, with bene®cial effects on other functions such as memory or they may in fact inhibit seizure activity.