History
The history is the most important diagnostic tool and should include the following:
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Birth, mother’s pregnancy, and developmental history
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CNS infections
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Head trauma
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Family history of seizures
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Seizure description by witness
The following are types of seizures seen in symptomatic generalized epilepsy (SGE):
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Myoclonic - Brief muscle jerks, single or in clusters, affecting any group of muscles, usually in the trunks and limbs
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Clonic - Repetitive and rhythmic jerking of limbs, neck, or face
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Tonic - Symmetric or asymmetric stiffening or posturing
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Atonic - Abrupt loss of muscle tone, usually truncal and resulting in a head drop or a fall
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Atypical absence - Similar to absence seizure but longer and with less clear onset and end
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Generalized tonic-clonic seizures
Epilepsy syndromes that are included in the category of SGE are discussed below.
Early myoclonic encephalopathy and early infantile epileptic encephalopathy with suppression burst/Ohtahara syndrome
As implied in the name, this has early onset (< 28 d). The first seizure can occur a few hours after birth and persist in both sleeping and waking hours. Early myoclonic encephalopathy has an erratic focal myoclonus, which can migrate throughout the infant's body. In Ohtahara syndrome, tonic spasms are the dominant seizure type, with little to no myoclonic seizures. [7, 8] As the brain continues in development, 40-60% of these infants have movements that can then evolve into flexor or extensor spasms seen in infantile spasm or West syndrome.
West syndrome
This consists of the characteristic triad of infantile spasms, mental retardation, and an EEG pattern of hypsarrhythmia. The infantile spasms can have a cluster of tonic flexion (transient neck, trunk, and extremity contraction) or extension of the axial body and limbs (backward extension of head and trunk and abduction of extremities). Focal cortical dysplasia can cause specific features such as focal tonic stiffening or focal movements such as head or eye deviation. [9]
Lennox-Gastaut syndrome
This consists of the characteristic triad of multiple seizure types, mental retardation, and EEG findings that include slow diffuse spike-wave complexes less than 2.5 Hz. [10, 11] Onset of symptoms begins approximately at age 2-6 years, with continuation into adult life. Of the various seizure types involved, atonic and tonic are most characteristic. Cognitive decline occurs within the first year of onset of seizures or can precede seizure onset. [2] The nosologic borders of Lennox-Gastaut syndrome are imprecise and somewhat arbitrary. "Lumpers" include virtually any type of SGE, whereas "splitters" require slow spike-wave complexes to make a diagnosis of Lennox-Gastaut syndrome.
Epilepsy with myoclonic atonic status and epilepsy with myoclonic absence
These can essentially be viewed as variants of Lennox-Gastaut syndrome. Both have a similar triad of multiple seizure types, mental retardation, and EEG findings with a 2-3 Hz spike-wave complex (slightly faster than Lennox-Gastaut syndrome). Age of onset is approximately 2 years, with first seizure type as generalized tonic-clonic. Later, the seizures predominately become myoclonic, atonic, and absence. The absence seizures involved in this syndrome are often prolonged, with bilateral limb myoclonus, differentiating it from idiopathic childhood absence seizures, for which seizure duration involves seconds and can be accompanied with only mild jerks of eyes, eyelids, or eyebrows.
Progressive myoclonic epilepsy
This is a group of epilepsies secondary to metabolic and neurodegenerative conditions. This consists of a triad of multiple seizure types, cerebellar impairment, and cognitive deterioration. The seizure onset is often in childhood and is characterized by intractable myoclonic jerks with tonic-clonic seizures and massive myoclonic seizures. [12, 13] The myoclonic jerks are multifocal and fragmentary, precipitated by posture or external stimuli such as sound, light, or touch. [14] Cerebellar degeneration presents as ataxia, dysarthria, and tremor. Dementia follows seizure onset and is progressive. Specific syndromes of progressive myoclonic epilepsy with key clinical features include Unverricht-Lundborg disease (Baltic myoclonus), myoclonus epilepsy with ragged red fibers (MERRF), neuronal ceroid lipofuscinoses (Batten disease), and sialidoses (cherry-red spot myoclonus syndrome).
It is important to recognize that many patients with SGE do not fit precisely into one of the above syndromes. In fact, beyond childhood, probably the majority of such patients have changed both clinically and based on EEG findings, so that they cannot be pigeon-holed into a named syndrome. These patients still belong under the broad category of SGE, and it is important for general neurologists to recognize this. Patients with Lennox-Gastaut, for example, when they grow up, do not become patients with complex partial seizures, an often-used wastebasket diagnosis. They are better categorized as having an SGE or "grown-up" Lennox-Gastaut syndrome. Now that medications have been approved with an indication for Lennox-Gastaut syndrome, this becomes more than a semantic or theoretical issue.
Physical Examination
Most patients with symptomatic generalized epilepsy (SGE) have neurological findings that reflect other abnormalities, including cognitive (mental retardation or development delay) and motor (cerebral palsy). [1, 7, 8]
Causes
Symptomatic generalized epilepsy (SGE) is defined as epilepsy secondary to an underlying etiology, either known (symptomatic) or presumed (cryptogenic). The insult associated with SGE can be prenatal (genetic or extrinsic), perinatal (birth trauma or anoxia), or postnatal (eg, trauma, infection).
Causes include specific entities such as metabolic disorders, chromosomal abnormalities, white matter disease, and obvious structural lesions.
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Atonic seizure. Abrupt loss of muscle tone is followed by clonic rhythmic movements. This type of seizure is typical for the symptomatic generalized epilepsies of the Lennox-Gastaut type.
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Electroencephalogram demonstrating hypsarrhythmia in infantile spasms. Note the chaotic high-amplitude background.
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Electroencephalogram demonstrating hypsarrhythmia. Note the electrodecremental response that is associated with a spasm in infantile spasms (ie, West syndrome).
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Slow (< 2.5 Hz) electroencephalographic spike and wave discharges associated with atypical absence seizures (ie, Lennox-Gastaut syndrome).
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Slow (< 2.5 Hz) electroencephalographic spike and wave discharges in atypical absence epilepsy (ie, Lennox-Gastaut syndrome).
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Spike, generalized. Significant spikes usually are followed by a slow wave, as shown here. This example also illustrates that generalized spikes are typically maximal frontally. This is typical of primary (ie, idiopathic, genetic) epilepsies. If burst lasted 3 seconds or more, it could be classified as spike-wave complexes.
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Slow spike-wave complexes. In addition to being slower, they are also less monomorphic than 3-Hz spike-wave complexes. With other findings, this often is seen in symptomatic/cryptogenic epilepsies of Lennox-Gastaut type.
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Slow spike-wave complexes. In addition to being slower, they are also less monomorphic than 3-Hz spike-wave complexes. With other findings, this often is seen in symptomatic/cryptogenic epilepsies of Lennox-Gastaut type.
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Hypsarrhythmia. High-amplitude slowing with no organized background and multifocal spikes (left and right frontal in this sample). This is phenotype of first year of life and is associated with West syndrome (ie, infantile spasms).
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Hypsarrhythmia. High-amplitude slowing (note scale) with no organized background and multifocal spikes (right frontal and left occipital in this sample). This is phenotype of first year of life and is associated with West syndrome (ie, infantile spasms).
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Generalized paroxysmal fast activity and electrodecrement. This pattern is characteristic of symptomatic/cryptogenic epilepsies of Lennox-Gastaut type and may be subclinical or associated with tonic or atonic seizures.
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Typical generalized tonic seizure in an adult patient with a "symptomatic" (now termed structural-metabolic) generalized epilepsy of the Lennox-Gastaut type.
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Typical generalized tonic seizure in a patient with a "symptomatic" (now termed structural-metabolic) generalized epilepsy of the Lennox-Gastaut type and severe static encephalopathy with cerebral palsy.
