Neonatal seizures may continue into the infantile period, or seizures may begin in an infant who seemed to be normal up to the time of the first convulsive attack. While the most common type of convulsion is the febrile seizure, not strictly a type of epilepsy, the most characteristic epilepsy at this age is the massive sudden myoclonic jerk of head and arms leading to flexion or, less often, to extension of the body (infantile spasms, salaam spasms). This form, which characterizes the West syndrome as described earlier, has many underlying causes. The same seizure type occurs in infants with tuberous sclerosis (diagnosed in infancy by the presence of hypopigmentated macules, or “ash-leaf spots”), phenylketonuria, or Sturge-Weber angiomatosis, but most often it is associated with other diseases beginning in this age period. Infantile spasms cease by the end of the second year and are replaced by focal and secondarily generalized seizures. They do not respond well to the usual antiepileptic medications. Some instances of infantile spasms may be due to a metabolic encephalopathy of unknown type or, a cortical dysgenesis (Jellinger). West syndrome is characterized by an EEG picture of large bilateral slow waves and multifocal spikes (hypsarrhythmia).
The Dravet syndrome, which includes myoclonic and focal seizures, occurs in this age group but is also relevant to adult practice as patients are recognized with persistence of resistant epilepsy of several types. In the past this form of epilepsy and developmental delay were attributed to a febrile illness or vaccination in infancy but it has become clear that the syndrome is the result of a loss of function mutation in a sodium channel gene (SCN1A in most cases). The initial seizures in these cases have been bought forward by a febrile episode or other neonatal event but they are subsequently characterized by unprovoked and treatment resistant episodes.
Febrile seizures represent a challenging problem in this age period. When febrile seizures are prolonged, focal, or accompanied by a neurologic deficit, they are referred to as complicated febrile seizure. These are distinguished from the benign familial febrile seizure syndrome discussed earlier in the chapter. While myoclonic activity with seizures in this age group raises concern of a serious condition, there is a common benign form with a heritable component and does not lead to developmental delay.
A number of focal epilepsies may appear for the first time during this age period and carry a good prognosis, that is, the neurologic and intellectual capacities remain relatively unimpaired and seizures may cease in adolescence. These disorders begin between 3 and 13 years of age and there is often a familial predisposition. Most are marked by distinctive focal spike activity that is accentuated by sleep (see earlier, in reference to benign childhood epilepsy with centrotemporal or occipital spikes). Several of these have been discussed earlier under the “Special Epileptic Syndromes.” In one form, benign childhood epilepsy with centrotemporal spikes, unilateral tonic or clonic contractions of the face and limbs recur repeatedly with or without paresthesia; anarthria may follow the seizure. There are central and temporal spikes in the EEG interictally. Less commonly, the focus originates in an occipital lobe with EEG spiking on eye closure. An acquired aphasia characterizes another disorder that was described by Landau and Kleffner to mark the beginning of an illness in which there are partial or generalized motor seizures and multifocal spike or spike-and-wave discharges in the EEG and deterioration of language function.
As in any age group, there are structural causes of seizures that include medial temporal sclerosis, described in several places in this chapter, tumor and arteriovenous malformation. The special case of Rasmussen encephalitis and intractable seizures has already been discussed under the “Special Epileptic Syndromes.”