This document discusses West Syndrome, a severe epilepsy syndrome seen in infants characterized by infantile spasms, a specific EEG pattern called hypsarrhythmia, and developmental delays. It provides details on the history, characteristics, subtypes, causes, diagnostic criteria including the hypsarrhythmia EEG pattern, treatment, and prognosis. Hypsarrhythmia is described as high-voltage slow waves and spikes that are chaotic, continuous, and seen in both awake and sleep states. Factors like sleep state, seizures, and time can influence the hypsarrhythmia pattern. Asymmetric or focal findings on EEG may indicate a symptomatic cause. Outcomes are often poor, with most patients developing other seizure types or Len

1. EEG IN WEST
SYNDROME:
Dr.Roopchand.PS
Senior Resident Academic
Department of Neurology
TDMC, Alappuzha

2. Overview
• Severe epilepsy syndrome composed of the triad of
infantile spasms, an interictal EEG pattern termed
hypsarrhythmia, and mental retardation.
• Dr W J West, gave the first detailed description of
infantile spasms.
• Published in The Lancet in 1841.
• Generalized Flexion Epilepsy, Infantile Epileptic
Encephalopathy, Infantile Myoclonic Encephalopathy,
jackknife convulsions, Massive Myoclonia , Salaam
spasms.

3. • Reflect abnormal interactions between the cortex and
brainstem structures.
• Insult to the immature CNS.
• Brain-adrenal axis.
• stressors in the immature brain produces an abnormal, excessive
secretion of corticotropin-releasing hormone (CRH), causing
spasms.
• Based on etiology classified in to
• Symptomatic
• Cryptogenic
• idiopathic.

4. • Two specific genetic defects have a phenotypic
presentation similar to that of the early onset of infantile
spasms.
• gene ARX mutation
• cyclin-dependent kinase-like protein 5 (CDKL5) mutation
• 2% of childhood epilepsies, 25% of epilepsy with onset in
the first year of life.
• Males are affected slightly more then females.
• Onset is before 12 mo of age.
• Peak onset between 4 to 6 mo.

5. • Only 14% of infants with symptomatic West syndrome
have normal or borderline-normal cognitive development.
• 50-70% of patients develop other seizure types.
• 18-50% of patients will develop Lennox-Gastaut
syndrome or some other form of symptomatic generalized
epilepsy.
• 70% dies before 20 yrs of age.

6. Hypsarrhythmia:
• Hypsarrhythmia is the characteristic interictal EEG
pattern.

7. • Chaotic, high- to extremely high–voltage, polymorphic
delta and theta rhythms with superimposed multifocal
spikes and wave discharges.
• Gibbs and Gibbs described hypsarrhythmia in 1952.
• Unilateral hypsarrhythmia and asymmetrical ictal EEG
changes during spasms are correlated with focal or
asymmetrical cerebral lesions on imaging studies.
• Hypsarrhythmia either disappears or improves during a
cluster of spasms and/or REM sleep.
• Hypsarrhythmia rarely persists beyond the age of 24
months.

8. Defining characteristics(Gibs and Gibs):
• Essentially continuous
• Present in both awake and sleep
• Consist of random high voltage slow waves and spikes.
• Spikes vary in location and duration – focal or multifocal
• Occasionally generalized discharges but never in a
rhythmic or highly organized pattern.

9. • Five variants of the "classical" hypsarrhythmic pattern
have been identified.
• Hypsarrhythmia with increased interhemispheric
synchronization (35%).
• Asymmetric hypsarrhythmia (12%).
• Hypsarrhythmia with a consistent focus of abnormal
discharge (26%).
• Hypsarrhythmia with episodes of voltage attenuation
(11%).
• Hypsarrhythmia without spike or sharp activity (7%).

10. Hypsarrhythmia with increased
interhemispheric synchronization:

11. Asymmetric hypsarrhythmia:

12. Focal Hypsarrhythmia:

13. Hypsarrhythmia with episodes of voltage
attenuation:

14. Factors influencing Hypsarrhythmia
pattern:
• It is a highly dynamic pattern:
• Sleep:
• NREM – increase in amplitude of waves, grouping of spikes,
sharps and slow waves, sometimes attenuation.
• REM: complete to near complete disappearance of hypsarrhythmia
pattern.
• Normalization can also be seen upon waking up.
• Ictal events:
• After a seizure episode there can be transient periods of decreased
abnormal activity and normalization of background.
• Evolution with time:
• Hypsarrhythmia pattern tends to decrease with time and
disappears by 5 to 7 years.

15. Precursors of hypsarrhythmia:
• Focal or multifocal spikes
• B/L parieto temporal dominant spikes
• Burst suppression pattern.

16. Significance of interictal pattern:
• Diagnostic value: very strong indicator of infantile spasms.
• Correlation with etiology:
• Asymmetric and focal findings correlate with a symptomatic
etiology.
• Hemi hypsarrhythmia pattern seen in cerebral dysgenesis
• HIE- absence of sleep pattern.
• Correlation with outcome:

17. ICTAL PATTERNS:
• Kellaway et al.
• Described 11 different patterns.
• High amplitude fast activity is the most commonest.
• Asymmetry indicates possible symptomatic etiology.

18. • Infantile Spasms: Diagnosis, Management and
Prognosis
• James D. Frost Jr., Richard A. Hrachovy - 2003