As discussed in Chapter 1, classification of epileptic seizure types has practical importance but also significant limitations. Historically used terms may not accurately reflect the complex pathophysiology or phenomenology of seizures. Generalized seizures involve synchronous epileptic discharges throughout the cerebral cortex, and are further distinguished by the terms primary or secondarily. Seizures that appear to have synchronous bihemispheric involvement at initiation (based on clinical and electrographic evidence) are primary generalized seizures and those that begin in a focal area of cortex and subsequently spread to involve both hemispheres are secondarily generalized. This distinction is not always straightforward, and a high index of suspicion should be maintained for focal onset seizures that appear generalized, because evaluation and treatment differs between generalized and focal epilepsies.
By age 2–4 years, children can manifest all of the generalized seizure types that are seen in older age groups—generalized tonic–clonic seizures (GTCs), absence seizures, myoclonic seizures, tonic seizures, and atonic/astatic seizures. Infantile spasms do not typically present at this age, and the occasional cases of late-onset infantile spasms are reviewed in Chapter 28.
Generalized seizures presenting in early childhood often fail to meet criteria for an epilepsy syndrome, or the syndrome may not be obvious at presentation.
The process of evaluation for a child in this age group, as with any child with epilepsy, begins with an accurate diagnosis of seizure, seizure classification, and, when possible, determination of etiology. A series of questions (see Box 11–1) should lead to the most appropriate diagnosis, which then guides further diagnostic evaluation and treatment decisions. This chapter is organized by clinical seizure type, and will focus on young children presenting with two or more unprovoked generalized seizures who do not fit into a definitive epilepsy syndrome.
BOX 11–1. KEY DIAGNOSTIC QUESTIONS
Was the event a seizure or not?
Was the seizure focal or generalized at onset?
Can a specific epilepsy syndrome be identified?
Does the history of physical exam suggest a cause?
If not, is a cause apparent on MRI?
If not, are there testable genetic etiologies, which would fit with the clinical picture?
GENERALIZED TONIC–CLONIC SEIZURES (GTCs)
CLASSIFICATION AND DIAGNOSIS
Most GTCs in this age group are, in fact, something else (FIG. 11-1). The first step in approaching the young child presenting with an event reported to be a GTC is to obtain a detailed description of the episode. Witnesses may describe a wide variety of clinical events (epileptic and nonepileptic) as "grand mal seizures" or "convulsions." In early childhood, events mimicking GTCs include breath-holding spells, syncope with subsequent convulsive movements, and gastroesophageal reflux. A careful description is essential for distinguishing epileptic from nonepileptic events. For example, breath-holding spells may be provoked by crying or a sudden fright, and are characterized by a respiratory pause ...