**6.1 Overview**

In 1970, Herman Doose reported seizures in 51 previously normal children between 1 and 5 years of age described as myoclonic and astatic, frequently combined with absences and GTCS and tonic seizures [75]. Doose suggested a genetic etiology [76] and later refined his criteria and emphasized that tonic seizures are rare [77].

In 1989, the ILAE recognized the syndrome of myoclonic-astatic epilepsy with a genetic predisposition, and in 2010 the term changed to "epilepsy with myoclonicatonic seizures" (EMAS). Features that define EMAS are (1) normal development previous to the start of seizures; (2) onset between 7 months and 6 years of age, of myoclonic, myoclonic-atonic, or atonic seizures; and (3) EEG with generalized spike or polyspike-and-wave discharges.

EMAS represents 1–2% of cases with childhood epilepsy and shows a variable clinical course and age-dependent spectrum. Onset peaks at about 3 years and is more prevalent in boys, ratio about 2:1. A long-term follow-up study showed a common evolution which was classified, according to the definitive seizure outcome, into favorable, intermediate, and unfavorable forms [78]. Cumulative percentage remission reached 40% within 6 months, 63% within 1 year, and 89% within 3 years after seizure onset [78]. Even in children with a favorable clinical course, seizures can be initially pharmacoresistant, sometimes demanding additional ACTH or ketogenic diet; in unfavorable patients, epilepsy remains refractory to treatment with the occurrence of long-lasting episodes of NCSE. Cognition is habitually normal during the first months of the disease, although patients are often severely hyperkinetic; intellectual outcomes range from favorable to unfavorable [79, 80].

### **6.2 Seizures: symptoms and semiology**

The main seizure types range from myoclonic to atonic. MS, atonic seizures (before called astatic), and myoclonic-atonic seizures typically occur a few days or weeks after the onset of GTCS or clonic seizures.

It is common for the first seizures to be clonic seizures or GTCS, which occur in normal children; sometimes they can be preceded by febrile seizures (FS). In a few months, the frequency of crises increases gradually and AA may appear. Nonconvulsive SS may be of myoclonic-atonic, myoclonic, or AA type and may be resistant to treatment. Some patients with a poor outcome may have brief tonic seizures.

The types of seizures observed in EMAS are:

	- Myoclonic flexor seizures with sudden flexion or extension of the head and trunk.
	- Myoclonic-atonic seizures with initial change as the myoclonic flexor type, but following falling is produced by loss of muscle tone.
	- Atonic seizures with sudden slumping or collapsing to the floor as a result of transient loss of muscle tone.

**91**

*Epileptic Encephalopathies in Infants and Children DOI: http://dx.doi.org/10.5772/intechopen.85378*

**6.3 Electroencephalography**

*6.3.1 Interictal background*

*6.3.2 Interictal abnormalities*

*6.3.3 Ictal EEG*

myoclonus.

concur to produce the typical drop.

4.Some patients may have prolonged recurrent AA with associated blurring of consciousness and often random segmental myoclonus or head nodding.

5.NCSE which consists of a cluster of myoclonic-astatic, MS, or AA. Clinically, we observe loss of contact or somnolence. Patients may have salivating and speech trouble ranging from dysarthria to mutism. Sometimes, erratic myoclonus in the face, the upper limbs, the eyelids, mouth, tongue, and fingers should be observed, associated with ataxic, hypotonia, tremor, and difficulty in walking.

6.Generalized tonic seizures with or without few clonic components occur during sleeping. When predominant, these seizures are associated with unfavorable outcome; they are resistant to treatment. When the tonic phase is preceded

Background activity is normal at the onset of the disease. A characteristic 4–7-Hz diffuse theta rhythm, usually predominating over the central-parietal areas (central theta waves), is often present, intermixed with normal waking activities and increasing during the drowsiness. In some children, background may be diffusely slow. During sleeping, physiological features are usually seen at the onset, while diffuse slowing with loss of sleep architecture can occur during the evolution,

In wakefulness there may be no epileptiform discharges. If this is present, generalized spike-waves discharges are at 2–3 Hz, predominant over the frontalcentral areas. They may show not consistent asymmetries between the hemispheres. Focal or multifocal spikes may also be present; these are rarely abundant and may predominate on one side, but not consistently so, and are not associated with focal slowing [11]. During sleeping, focal and generalized spike-wave discharges may

Generalized bilaterally synchronous single or multiple spike-and-wave discharges with 2–4 Hz frequency are commonly associated with all three seizures types that produce drop attacks, although spike-wave discharges are briefer for

The EMG correlate of the jerk is a burst of muscle activity lasting 100 ms; this is followed by a post-myoclonic silent period of EMG inhibition that lasts for 60–500 ms, which is synchronous for the recorded muscles and time-locked to the onset of the slow wave [78]. Both the brisk jerk and the post-myoclonic silent period

AA corresponds of generalized irregular spike-wave discharges at 1.5–3 Hz. During

NCSE, EEG shows no normal background activity, is characterized by diffuse and irregular spikes and slow waves persisting continuously throughout the episode, and is in combination with erratic myoclonus recorded on the EMG. Generalized tonic seizures correspond to burst of generalized spikes during sleep and eventually wakefulness.

by a myoclonic jerk, seizures are termed "myotonic."

mainly in the severe forms of the spectrum [11].

increase and acquire a typical polyspike component.

*Epilepsy - Advances in Diagnosis and Therapy*

spike or polyspike-and-wave discharges.

from favorable to unfavorable [79, 80].

**6.2 Seizures: symptoms and semiology**

weeks after the onset of GTCS or clonic seizures.

The types of seizures observed in EMAS are:

transient loss of muscle tone.

decreasing frequency of the clonic jerks.

and EMG polygraphy.

trunk.

seconds.

In 1989, the ILAE recognized the syndrome of myoclonic-astatic epilepsy with a genetic predisposition, and in 2010 the term changed to "epilepsy with myoclonicatonic seizures" (EMAS). Features that define EMAS are (1) normal development previous to the start of seizures; (2) onset between 7 months and 6 years of age, of myoclonic, myoclonic-atonic, or atonic seizures; and (3) EEG with generalized

EMAS represents 1–2% of cases with childhood epilepsy and shows a variable clinical course and age-dependent spectrum. Onset peaks at about 3 years and is more prevalent in boys, ratio about 2:1. A long-term follow-up study showed a common evolution which was classified, according to the definitive seizure outcome, into favorable, intermediate, and unfavorable forms [78]. Cumulative percentage remission reached 40% within 6 months, 63% within 1 year, and 89% within 3 years after seizure onset [78]. Even in children with a favorable clinical course, seizures can be initially pharmacoresistant, sometimes demanding additional ACTH or ketogenic diet; in unfavorable patients, epilepsy remains refractory to treatment with the occurrence of long-lasting episodes of NCSE. Cognition is habitually normal during the first months of the disease, although patients are often severely hyperkinetic; intellectual outcomes range

The main seizure types range from myoclonic to atonic. MS, atonic seizures (before called astatic), and myoclonic-atonic seizures typically occur a few days or

It is common for the first seizures to be clonic seizures or GTCS, which occur in normal children; sometimes they can be preceded by febrile seizures (FS). In a few months, the frequency of crises increases gradually and AA may appear. Nonconvulsive SS may be of myoclonic-atonic, myoclonic, or AA type and may be resistant to treatment. Some patients with a poor outcome may have brief tonic

1.Epileptic drop attacks or seizures that cause falls, which can be of three different types taking account the postural change, the temporal sequence of falling,

• Myoclonic flexor seizures with sudden flexion or extension of the head and

• Myoclonic-atonic seizures with initial change as the myoclonic flexor type,

• Atonic seizures with sudden slumping or collapsing to the floor as a result of

2.Generalized clonic seizures occur during both wakefulness and sleep. The clonic component commonly appears as the repetition of massive MS. Clonic movements habitually increase in frequency and may become very rapid resulting in a "clonic vibratory" seizure that usually ends with gradually

3.GTCS, in which clonic component is preceded by a tonic phase lasting a few

but following falling is produced by loss of muscle tone.

**90**

seizures.

