Symptomatic Generalized Epilepsy Workup

Updated: Dec 11, 2018
  • Author: Emily Nakagawa, DO, MPH; Chief Editor: Selim R Benbadis, MD  more...
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Workup

Laboratory Studies

The following studies are intended to determine the etiology:

  • Electrolyte evaluation

  • CBC count

  • Metabolic testing

  • Genetic testing

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Imaging Studies for SGE

MRI of the brain is also used to determine the etiology.

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Other Tests for SGE

EEG

The EEG in symptomatic generalized epilepsy (SGE) typically reveals epileptiform abnormalities and other evidence of diffuse brain dysfunction (various degrees of slowing). As the brain develops from neonate to adolescent, the epileptiform abnormalities can also change.

In neonates with SGE, early myoclonic encephalopathy and Ohtahara syndrome have EEG findings with a suppression-burst pattern. The myoclonic jerks of early myoclonic encephalopathy correlate with the burst of spikes, sharp waves, and slow waves lasting 1-5 seconds on EEG, with periods of suppression of 3-10 seconds with no normal background. [7, 15]

The EEG in Ohtahara syndrome shows bursts of 2-6 seconds of wide amplitude spikes and polyspikes that alternate with 3-8 seconds of suppressed electrical activity. Later in infancy, the burst-suppression pattern is replaced by continuous multifocal spikes and slow waves of large amplitude or hypsarrhythmia, as is seen in infantile spasm. [1] The hypsarrhythmia represents spread of epileptic activity when the brain has not developed inhibition. [9]

As the brain continues to mature, EEG patterns in children with SGE can evolve into a generalized, high-amplitude, synchronous, slow spike, polyspike, and slow wave discharges of 1.5-2.5 Hz, as is seen in Lennox-Gastaut syndrome. [6] The interictal EEG shows a generalized slow spike-wave pattern, further activated by drowsiness and sleep. [16]

EEG findings progressive myoclonic epilepsy reveal a specific pattern unique to the syndrome. EEG in Lafora disease reveals occipital spikes in 50% of patients.

Unverricht-Lundborg disease EEG findings reveal background slowing in theta frequency, with a 3-5 Hz polyspike, and waves discharge with sporadic focal spikes and wave discharges.

EEG in patients with sialidosis reveals progressive slowing of background activity with bilateral spike and wave activity, which is photosensitive.

Beyond early childhood and almost regardless of etiology, the typical EEG of SGE includes slow (< 2.5 Hz) spike and wave complexes and multifocal spikes. Ictal patterns are described in EEG-video monitoring.

For more information, see EEG in Common Epilepsy Syndromes and Generalized Epilepsies on EEG.

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Procedures for SGE

No procedures are indicated, except for in specific neurodegenerative diseases that are typically investigated during childhood. If the latter conditions are suspected, then cerebrospinal fluid analysis should be performed. If a specific genetic condition is suspected, then chromosomal analysis or skin biopsy for electron microscopy may be diagnostic.

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