EEG IN WESTSYNDROME:Dr.Roopchand.PSSenior Resident AcademicDepartment of NeurologyTDMC, 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 increasedinterhemispheric synchronization:
Hypsarrhythmia with episodes of voltageattenuation:
Factors influencing Hypsarrhythmiapattern:• 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