What is the role of interictal electroencephalogram in the workup of infantile spasm (West syndrome)?

Updated: Jan 11, 2019
  • Author: Tracy A Glauser, MD; Chief Editor: Stephen L Nelson, Jr, MD, PhD, FAACPDM, FAAN, FAAP  more...
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Answer

Hypsarrhythmia (seen in the image below) is the characteristic interictal EEG pattern. It consists of chaotic, high- to extremely high–voltage, polymorphic delta and theta rhythms with superimposed multifocal spikes and wave discharges. Multiple variations of this pattern are possible, including focal or asymmetrical hypsarrhythmia.

Mountainous, chaotic, disorganized rhythms with su Mountainous, chaotic, disorganized rhythms with superimposed multifocal spikes demonstrating hypsarrhythmia in a boy aged 8 months with infantile spasms and developmental delay. Courtesy of E Wyllie.

In a study of 77 patients with infantile spasms, unilateral hypsarrhythmia and asymmetrical ictal EEG changes during spasms often occurred together and correlated with focal or asymmetrical cerebral lesions on imaging studies. Patients with symmetrical hypsarrhythmia and infantile spasms rarely had focal or asymmetrical cerebral lesions on imaging studies (most had structural diffuse brain lesions), and overall they had better chances for a normal outcome.

In a study of 26 patients with infantile spasms, 6 patients (23%) had asymmetrical hypsarrhythmia. All 6 had symptomatic infantile spasms and 5 had focal abnormalities on examination or imaging study (4 ipsilateral to the lesion, 1 contralateral). These focal abnormalities may identify a subset of patients with infantile spasms who are candidates for focal cortical resections.


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