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Epilepsia. 2008 Nov;49(11):1859-64. doi: 10.1111/j.1528-1167.2008.01715.x. Epub 2008 Jul 9.

Electroencephalographic evolution of hypsarrhythmia: toward an early treatment option.

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Center of Developmental Neurology and Epileptology, Frankfurt, Germany.



A retrospective study for a classification of prehypsarrhythmic elecroencephalographies (EEGs) was carried out to enable an early treatment option for West syndrome.


Out of 39 infants with symptomatic West syndrome, 18 infants (age 3-14 months) with 61 serial non-REM sleep EEG records of the prehypsarrhythmic phase were identified. The prehypsarrhythmic phase encompassed 2 to 13 months (mean 4.5 months) after an initial insult. A classification system of three EEG types corresponding to the clinical states prior to West syndrome occurrence was developed. In addition, follow-up of all patients presenting with type 2 EEGs (n = 22) was evaluated.


Three clinical states and corresponding EEG types were classified. Clinical state 1 (weeks to months, silent phase) presented with (multi-)focal epileptic discharges <50% of the non-REM EEG recording time (type 1 EEG). Clinical state 2 (several weeks, beginning mental deterioration) was accompanied by type 2 EEG with bihemispheric epileptic discharges >50% of the non-REM EEG recording time within abnormal background activity (imminent hypsarrhythmia). Clinical state 3 (mental deterioration) was characterized by hypsarryhthmia. Interrater reliability of seven blinded raters was good (median weighted kappa 0.67). Out of 22 patients presenting with type 2 EEGs, two were lost for follow-up, and 16 developed West syndrome, whereas four were treated early with anti-epileptic drugs and remained stable.


Infants with West syndrome could be reliably identified several weeks before the occurrence of hypsarrhythmia by a typical EEG pattern (type 2), thereby opening the way for early intervention studies.

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