Diagnostic Criteria for Infantile Spasms and West Syndrome

West syndrome is characterized by a specific type of seizure ( infantile spasms) and developmental regression.

The gold standard method of diagnosing infantile spasms is to capture them on video-EEG to confirm the ictal correlate of the seizure.

Guidance for the diagnosis of infantile spasms

Required either 1 of:

• Video-EEG confirmed spasms with typical ictal correlate
• Either home video of spasms with typical features or definite typical clustering spasms by history, PLUS probable or definite epileptic encephalopathy on EEG

The 2021 BASED score*

BASED score	Description
0	Normal
1	Any definite nonepileptiform abnormality
2	<3 spike foci AND no channel with abnormal high amplitude
3	≥3 spike foci <50% of one second bins AND no channel with abnormal high amplitude, OR <3 spike foci but ≥1 channel with abnormal high amplitude
4 (Probable EE)	≥3 spike foci <50% of one second bins AND ≥1 channel with abnormal high amplitude, OR Not meeting criteria for 5 but includes GMFS or paroxysmal voltage attenuations
5 (Definite EE)	≥3 spike foci that are ≥50% of one second bins

BASED: Burden of AmplitudeS and Epileptiform Discharges, GMFS: grouped multifocal spikes, EE: epileptic encephalopathy
BASED Score Rules: Apply score 3-5 to the most epileptic 5 min epoch; if no score reached, apply score 0-2 to
the remainder of the study
≥3 Spike Foci Rules:

1. May be at least one from each hemisphere OR all from one hemisphere (may include midline)
2. If ≥3 spike foci in entire study but no 3 spike foci within 5 min, and no channel with abnormal high amplitude, BASED score is 2 + uncommon multifocal spikes

Spike Burden Rules:

1.  % one second bins that include 1 or more spikes in the most epileptic 5 min epoch
2. Calculate ≥50% ≥3 spike foci by determining if 10 or more 15 s pages in a 5 min epoch include ≥8/15 one second bins with a spike

Amplitude Rules:

1. Peak-to-peak amplitude on a longitudinal bipolar montage, refers to background waves and excludes 1) the slow wave of a preceding spike and the field of these waves in other channels, 2) hypnagogic patterns, and 3) arousal rhythms
2. Waves must be common: present at least once in 10 or more 15 s pages in a 5 min epoch
3. Abnormal high amplitude:
   a. ≥200 mv: Fp1-F7, F7-T3, Fp1-F3, F3-C3, C3-P3, Fp2-F4, F4-C4, C4-P4, C4-P4, Fp2-F8, F8-T4
   b. ≥300 mv: T3-T5, T4-T6
   c. Excluded: Fz-Cz, Cz-Pz, T5-O1, P3-O1, P4-O2, T6-O2

Grouped Multifocal Spikes Definition:

1. At least 2 different spike foci in each hemisphere within a fairly well delineated group (may include midline)
2. For hemispheric grouping, at least 3 different spike foci in one hemisphere (may include midline) within a fairly well delineated group

Paroxysmal Voltage Attenuation Definition:

1. Definite sudden change from ongoing background activities appearing as a relative attenuation most often lasting one second (but may last several seconds), often occurring after an epileptic discharge, and usually diffuse (but may be present in only one hemisphere)

Remission Rules:

1. Pretreatment score of 4 or 5, must improve to ≤3
2. Pretreatment score of 3, must improve to ≤2

 

Guidance for the diagnosis of West syndrome

Required Features:	Required 1 of:	Exclusionary Features:
Infantile Spasms Age 2 months to 2 years	Developmental abnormalities with definitively epileptic EEG No developmental abnormalities but with Probable or Definite EE	Presence of alternative age-dependent DEE such as: Early Infantile DEE Late Infantile DEE Lennox-Gastaut syndrome

EE, epileptic encephalopathy; DEE, developmental and epileptic encephalopathy

 

References:

1. Mytinger JR. Definitions and Diagnostic Criteria for Infantile Spasms and West Syndrome – Historical Perspectives and Practical Considerations. Semin Pediatr Neurol. 2021 Jul;38:100893. [Medline]
2. Chopra SS. Infantile Spasms and West Syndrome – A Clinician’s Perspective. Indian J Pediatr. 2020 Dec;87(12):1040-1046. [Medline]

 

Created Jan 26, 2022.