hypsarrhythmia
Pronunciation: hip-sah-RITH-mee-ah
Chaotic, high-amplitude EEG pattern with multifocal spikes and slow waves, characteristic of infantile spasms syndrome.
Full Definition
Hypsarrhythmia is a distinctive, severely abnormal EEG pattern characterized by chaotic, high-amplitude (typically >200 microvolts) activity with multifocal spikes, sharp waves, and slow waves occurring asynchronously across both hemispheres. This pattern is pathognomonic of West syndrome (infantile spasms) and represents one of the most disorganized EEG patterns encountered in clinical neurophysiology. The term combines 'hypsi' (high) and 'arrhythmia' (irregular rhythm), reflecting the pattern's high amplitude and chaotic nature. Modified forms may be seen during treatment or evolution of the condition.
Usage
Usage note: Pathognomonic finding requiring immediate clinical attention and treatment.
In Context
- "The EEG demonstrated classic hypsarrhythmia with high-amplitude chaotic activity and multifocal spikes." — Infantile spasms evaluation
- "Treatment with ACTH resulted in resolution of the hypsarrhythmia pattern and cessation of spasms." — Treatment response report