6 - Neurophysiological studies of alterations in seizure susceptibility during brain development

Summary

Introduction

The basic processes responsible for seizures in an infant's brain are likely to be quite different from those in the central nervous system of an adult. The nervous system of a neonate is so unlike its mature counterpart in basic anatomical, physiological, and metabolic properties that it is obvious even to the most casual observer that many critical issues of pediatric epileptology are different from those addressed by epileptologists concerned with controlling seizures in adults.

Many epileptic syndromes in children occur during restricted phases of nervous system development (O'Donohoue, 1985; Aicardi, 1986; Tharp, 1987); the phrase ‘age-specific epilepsies’, therefore, has been used to describe these disorders. For example, infantile spasms are observed usually between three months and three years of age (Lacy & Penry, 1976). Thereafter this seizure disorder may evolve into a different form of epilepsy only later to emerge as another syndrome in adulthood. At each stage the seizures are likely to differ not only in their clinical and electrographic features but also in their response to medication (Freeman, 1987).

On the other hand some seizure disorders of childhood have clear counterparts in adulthood. Simple and complex partial seizures are examples (Holmes, 1986, 1987; Wyllie et al., 1989). Characteristically, these seizures arise from localized regions of the brain and are often referred to in experimental epilepsy research as focal seizures. In both infants and adults, the complex partial epilepsies commonly originate from the temporal lobe.