Which findings on EEG are characteristic of Lennox-Gastaut syndrome (LGS)?

Updated: Nov 09, 2018
  • Author: Koshi A Cherian, MD; Chief Editor: Amy Kao, MD  more...
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Answer

No laboratory investigations are known to aid in the diagnosis of LGS.

EEG (waking and sleep) is an essential part of the workup. Interictal EEG may demonstrate the following characteristics:

  • A slow background that can be constant or transient

  • Awake – Diffuse slow spike wave

  • Non-REM sleep – Discharges that are more generalized and more frequent, consisting of polyspikes and slow waves

  • REM sleep – Decreased spike waves

Ictal EEG may demonstrate the following characteristics:

  • Tonic seizure – Diffuse, rapid, low-amplitude activity pattern that progressively decreases in frequency and increases in amplitude; may be preceded by a brief generalized discharge of slow spike waves or flattening of the recording or followed by diffuse slow waves and slow spike waves; no postictal flattening

  • Atypical absence seizure – Diffuse, slow, and irregular spike waves; occasionally, discharges of rapid rhythms preceded by flattening of the record for 1-2 seconds, followed by progressive development of irregular fast rhythm in anterior and central regions and ending with brief spike waves

  • Atonic, massive myoclonic, or myoclonic-atonic seizure – Slow spike waves, polyspike waves, or rapid diffuse rhythms

  • Absence status epilepticus – Continuous spike wave discharges, usually at a lower frequency than at baseline, and rapid rhythms during tonic status epilepticus


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