Hypsarrhythmia: EEG Characteristics, Clinical and Etiological Factors, and Prognosis

Background/Purpose: Hypsarrhythmia occurs in children with West syndrome. However, hypsarrhythmia-like EEG changes can also occur in other pathological conditions (for example, nonconvulsive status epilepticus in Lennox-Gastaut syndrome, in certain genetic syndromes in combination with pharmacoresistant epileptic seizures). Hypsarrhythmia in combination with clinical and etiological peculiarities can play an important role as prognostic factors influencing the interruption of epileptic seizures and helping to maintain remission.

Methods: A total of 50 EEG studies with various forms of hypsarrhythmia in combination with clinical features and etiology were analyzed. Children aged 3 months to 11 years with West syndrome, mutation in the X-linked CDKL-5 gene, Down syndrome, and Lennox-Gastaut syndrome (hypsarrhythmia-like changes in non-convulsive status epilepticus).

Results: EEG characteristics and clinical and etiological factors associated with a “relatively” good prognosis: a higher proportion of rapid background activity (> 30-40% theta), absence of an electrode decrement, low asymmetry and no synchronization in the EEG; idiopathic and cryptogenic etiology of West syndrome; early initiation of therapy and response to medication. The prognosis is unfavorable: persistence of EEG changes, synchronization and asymmetrical hypsarrhythmia. Asymmetric hypsarrhythmia and unilateral, focal character indicate a structural lesion.

Conclusion: For West syndrome, hypsarrhythmia has been shown to have no prognostic value. The prognosis of hypsarhythmia in terms of mental functions and subsequent epilepsies in symptomatic forms with structural lesions and genetic abnormalities is poor. Electrophysiological parameters must be supplemented with clinical and technical findings to assess the prognosis. The prognosis is more favorable in idiopathic and cryptogenic cases. Further studies on a larger group are needed to test the role of EEG criteria as a prognostic marker.

Publication History

Article published online:
28 October 2021