Hypsarrhythmia
Pronunciation: hip-sah-RITH-me-ah
A chaotic, disorganized EEG pattern with high-voltage, multifocal spikes characteristic of West syndrome.
Full Definition
Hypsarrhythmia is a distinctive and severely abnormal electroencephalographic pattern characterized by continuous, high-voltage (typically >300 microvolts), asynchronous slow waves mixed with multifocal spikes and sharp waves that appear chaotically distributed across all brain regions. This pattern is pathognomonic for West syndrome and represents one of the most disorganized EEG patterns seen in clinical neurophysiology. The term, coined by Gibbs and Gibbs in 1952, derives from the Greek words 'hypsi' (high) and 'arrhythmia' (without rhythm). The pattern may be modified by sleep states and can evolve over time with treatment or disease progression.
Usage
Usage note: From Greek 'hypsi' (high) + 'arrhythmia' (without rhythm); pathognomonic for West syndrome.
In Context
- "The EEG demonstrated classic hypsarrhythmia with high-voltage chaotic activity during wakefulness." — EEG interpretation report
- "Resolution of hypsarrhythmia after ACTH treatment correlated with cessation of infantile spasms." — Treatment response evaluation