EEG IN WEST SYNDROME:Dr.Roopchand.PS

Senior Resident Academic

Department of Neurology

TDMC, Alappuzha

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.

• 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.

• 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.

• 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.

Hypsarrhythmia:• Hypsarrhythmia is the characteristic interictal EEG

pattern.

• 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.

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.

• 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%).

Hypsarrhythmia with increased interhemispheric synchronization:

Asymmetric hypsarrhythmia:

Focal Hypsarrhythmia:

Hypsarrhythmia with episodes of voltage attenuation:

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.

Precursors of hypsarrhythmia:

• Focal or multifocal spikes• B/L parieto temporal dominant spikes• Burst suppression pattern.

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:

ICTAL PATTERNS:

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

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

Thank You