Pediatric Seizures

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Pediatric Seizures

Douglas R. Nordli, Jr. and Phillip L. Pearl

Clinical and electroencephalogram (EEG) analysis of pediatric seizures relies on the International League Against Epilepsy classification scheme of focal versus generalized onset as well as the electroclinical syndromes and subtle aspects of infantile seizures. Generalized tonic–clonic (GTC) seizures can be seen at nearly any age, but are rarely seen in infancy. Myoclonic seizures are very brief contractures of the muscles causing an abrupt lighting fast jerk. Myoclonic–atonic seizures were formerly known as myoclonic–astatic seizures. Myoclonic–tonic seizures may be seen across the pediatric age span, but are most commonly observed in infants and young children. Generalized clonic seizures are rarely seen outside of the early infantile period. Most focal seizures begin with focal or regional rhythmic epileptiform activity that slows in frequency as they build in amplitude. Epileptic spasm is a term used to broadly cover all of the different types of spasms recorded throughout the age spectrum.

electroencephalogram, epileptic spasm, focal seizures, generalized clonic seizures, generalized tonic seizures, myoclonic seizures, pediatric seizures

Electroencephalography, Epilepsies, Myoclonic, Pediatrics, Seizures, Spasm

The classification of seizures was revised by the International League Against Epilepsy (ILAE) in 2017 to categories of focal, generalized, and unknown onset with further subdivisions based on their motor versus nonmotor characteristics. Instead of relegating absence, tonic, myoclonic, clonic, tonic–clonic, and atonic to generalized seizures only, this allowed for an expansive view of seizure semiology accounting for the potential for tonic, clonic, myoclonic, and other seizure types to have either focal or generalized onset (Table 6.1).

The epilepsies were also reclassified, no longer as symptomatic, cryptogenic, and idiopathic, but as focal, generalized, combined generalized and focal, or unknown in type. Additionally and especially important in pediatric epilepsy, the epilepsy types, along with their various etiologies, for example, structural, genetic, infectious, metabolic, immune, and unknown, and comorbidities were classified into the epilepsy syndromes. The epilepsy syndromes are time-honored constellations of electroclinical correlation affording much meaning to the clinician’s view of an individual’s epilepsy along with the crucial expectant management issues including treatment approach and prognosis, and are often presented based on their age of onset (Table 6.2).

TABLE 6.1. ILAE 2017 expanded classification of seizure types

I. FOCAL ONSET

A. Aware or Impaired Awareness

B. Motor Onset

Automatisms, atonic, clonic, epileptic spasms, hyperkinetic, myoclonic, tonic

C. Nonmotor Onset

Autonomic, behavior arrest, cognitive, emotional, sensory

D. Focal to bilateral tonic–clonic

II. GENERALIZED ONSET

A. Motor

Tonic–clonic, clonic, tonic, myoclonic, myoclonic–tonic–clonic, myoclonic–atonic, atonic, epilepsy spasms

B. Nonmotor (absence)

Typical, atypical, myoclonic, eyelid myoclonia

III. UNKNOWN ONSET

A. Motor

Tonic–clonic, epileptic spasms

B. Nonmotor

Behavior arrest

IV. UNCLASSIFIED

Note: ILAE, International League Against Epilepsy.

124TABLE 6.2. Epilepsy syndromes by age of onset

Neonatal Onset

Benign (idiopathic) neonatal seizures (fifth-day fits)

Benign familial neonatal epilepsy

Early infantile epileptic encephalopathy (Ohtahara syndrome)

Early myoclonic encephalopathy

Infantile Onset

Myoclonic epilepsy in infancy (benign Dravet variant)

Benign epilepsy of infancy

Benign familial infantile epilepsy

Epilepsy of infancy with migrating focal seizures

Hemiconvulsion-hemiplegia-epilepsy syndrome

West syndrome (infantile spasms, hypsarhythmia; to be distinguished from benign myoclonus of early infancy, which is not an epilepsy)

Severe myoclonic epilepsy of infancy (classic Dravet syndrome)

Myoclonic encephalopathies in nonprogressive disorders

Childhood

Genetic epilepsy with febrile seizures plus (can begin in infancy)

Early onset childhood occipital epilepsy (Panayiotopoulos syndrome)

Myoclonic–atonic (formerly astatic) epilepsy (Doose syndrome)

Self-limited epilepsy with centrotemporal spikes (Benign Rolandic epilepsy)

Late-onset childhood occipital epilepsy (Gastaut type)

Epilepsy with myoclonic absences (Tassinari syndrome)

Lennox-Gastaut syndrome

Epileptic encephalopathy with continuous spike-and-wave in slow sleep

Acquired epileptic aphasia (Landau–Kleffner syndrome)

Childhood absence epilepsy (pyknolepsy)

Generalized epilepsy with eyelid myoclonia (Jeavons syndrome)

Adolescence to Adult Onset

Juvenile absence epilepsy

Juvenile myoclonic epilepsy

Epilepsy with generalized tonic–clonic seizures alone

Progressive myoclonus epilepsies

Mesial temporal lobe epilepsy with hippocampal sclerosis

Autosomal dominant focal epilepsy with auditory features

Autosomal dominant nocturnal frontal lobe epilepsy

Syndromes With Less Specific Age Relationship

Familial focal epilepsy with variable foci (childhood to adult)

Reflex epilepsies

125GENERALIZED SEIZURES

Generalized tonic–clonic (GTC) seizures can be seen at nearly any age, but are rarely seen in infancy. These seizures often begin with brief clonic jerking or a few myoclonic jerks that are rapidly followed by the stiffening phase (tonic) and culminating in the rhythmic jerking phase (clonic). The earliest manifestation is often eye opening, often with upward deviation of the eyes. The tonic phase is caused by sustained contractions of the muscles, often lasting 10 to 20 sec. A wide variety of postures may be seen in this phase, but many times the arms are flexed at the elbows while the legs are fully extended. A forced exhalation at this stage can produce a loud noise that alerts parents to the presence of the seizure. Repeated jerking of the limbs characterizes the clonic portion of the seizure which often lasts 30 sec to a minute. There may be accompanying bladder or bowel incontinence and tongue biting can occur. Afterward, the child is temporarily unresponsive. Breathing resumes with a deep breath and the child gradually returns to normal function after a variable postictal phase. Labored postictal breathing is known as stertorous respirations.

**FIGURE 6.1.** Generalized tonic–clonic. The early tonic phase of a generalized tonic–clonic seizure is shown from the recording done on a 2.5-year-old.

The ictal EEG often begins with diffuse spikes, correlating with the brief clonic or myoclonic onset. The tonic phase may begin with a brief epoch of diffuse flattening (Figure 6.1), followed by diffuse rhythmic low voltage beta activity, and finally a sustained 10 to 12 Hz rhythm (epileptic recruiting rhythm).

**FIGURE 6.2.** Generalized tonic–clonic. The clonic phase of a generalized tonic–clonic seizure is shown from the same child in Figure 6.1.

During the clonic phase, there are repeated bursts of high-amplitude spike or polyspike-wave complexes correlating with the individual jerks (Figure 6.2). In the postictal period, there is either profound background suppression or diffuse background slowing. The polygraphic recording will show a rectangular shape in the tonic phase of the seizure. This is due to the abundant, very fast reciprocal tonic contractions of the muscles. This is followed by rhythmic contractions during the clonic phase. In the immediate postictal epoch the muscle tone will be very low and the polygraphic channels will be flat.

**FIGURE 6.3.** Typical absence seizure manifest as a 5-second burst of 3 Hz generalized spike-and-waves with anterior predominance.

Typical and atypical absence seizures are most easily distinguished by characteristics defined by their EEG. Typical absence seizures have a faster repetition rate (3–4 Hz), whereas the ictal accompaniment of atypical absences seizures has a repetition rate less than or equal to 2.5 Hz. Atypical absence seizures have an indiscrete onset and offset and are more prolonged than typical absence seizures. Atypical absence seizures typically occur in the encephalopathic generalized epilepsies.

In contrast, typical absence seizures are brief events with a very distinct start and finish. There are two required features: there is some impairment in consciousness with the seizure and the EEG demonstrates bursts of generalized 3- to 4-Hz spike-and-wave activity (Figure 6.3). Some experts further divide typical absence seizures into simple and complex categories, depending on the presence (complex) or lack (simple) of motor features. In the current ILAE classification scheme, absence seizures are conflated with the nonmotor seizures of generalized onset, and also include myoclonic absence and eyelid myoclonia. The former is typical of the myoclonic epilepsy syndrome of Tassinari, while the latter is associated with Jeavons syndrome (Table 6.2).