One principle that emerges is that the form taken by seizures in early life is in part age-linked. Neonatal seizures are predominantly partial or focal; infantile seizures take the form of myoclonic flexor (sometimes extensor) spasms; and the various forms of petit mal are essentially diseases of childhood (4 to 13 years). The motor phenomena of epilepsy in young children are often termed myoclonic, but this should not be confused with other, later-occurring epilepsies that are endowed with the same name. Furthermore, certain epileptic states tend to occur only during certain epochs of life—one type of febrile seizure from 6 months to 6 years, generalized or temporal spike-wave activity with benign motor and complex partial seizures from 6 to 16 years, and juvenile myoclonic epilepsy in the midand late-adolescent years. In general, idiopathic epilepsy, so called because the cause cannot be determined, is predominantly a pediatric neurologic problem. This is not to say that seizures of unknown cause do not occur for the first time in adult life but rather that the onset of such seizures is far more frequent in childhood and tends to diminish once adulthood is reached.
The clinical characteristics of infantile and childhood seizures, including those of genetic origin, are fully described in Chap. 15.
Two clinical types can be recognized based on the adequacy of motor skills that are acquired in parallel with cognitive skills. In the first, the essential characteristic is that, almost from birth, the infant is delayed in all aspects of development. There is a tendency to sleep more, to be less demanding of nourishment, to move less than normal, and to suck poorly and regurgitate. Parents comment on how good their baby is, how little he troubles them by crying. As the months pass, every expected achievement is late. The baby is usually more hypotonic and turns over, sits unsupported, and walks later than the normal infant. Yet despite these obvious motor delays, there is later no sign of paralysis, ataxia, chorea, or athetosis. These babies do not smile at the usual time and take little notice of the mother or other persons or objects in their environment. They are less attentive to visual, and often to auditory, stimuli, to the point where questions may be raised about blindness or deafness. Certain phases of normal development, such as hand regard, may persist beyond the sixth month, when they are normally replaced by other activities. Mouthing (putting everything in the mouth) and slobbering, which should end by 1 year of age, also persist. There are only fleeting signs of interest in toys, and the impersistence of attention becomes increasingly prominent. Vocalizations are scant, often guttural, piercing, or high-pitched and feeble. Babbling is not replaced by attempts at word formation at the usual time.
In the second type, early motor milestones (supporting the head, rolling over, sitting, standing, and walking) are attained approximately at their normal times, yet the infant is inattentive and slow in learning the usual nursery tricks. It seems as though motor development had somehow escaped the process of developmental delay. There may, however, be aimless overactivity and persistence of rhythmic movements, grinding of the teeth (bruxism), and hypotonia.
Because the developmental sequence of motor function and speech may be normal, even to the point where the baby acquires a few words by the end of the first year, the examiner may be misled into thinking that the delayed infant was at first normal and had then deteriorated. In such infants it can even be shown that various test procedures yield lower scores with progressing age (from 3 years onward); this is not the result of a decline in ability but of the fact that the tests are not comparable at different times. In the early years, the tests are weighted toward sensorimotor functions and after that toward perception, memory, and concept formation. Interestingly, the development of language depends upon both groups of functions, needing a certain maturation of the auditory and motor apparatus at the start and highly specialized cognitive skills for continued development. These and other aspects of development of speech and language were considered earlier in this chapter and are commented on further in Chaps. 22 and 27.