Hypsarrhythmia is very chaotic and disorganized brain electrical activity with no recognizable pattern, whereas a normal brain electrical activity shows clear separation between each signal and visible pattern. It is an abnormal
interictal pattern, consisting of high amplitude and irregular waves and spikes in a background of chaotic and disorganized activity seen on
electroencephalogram
Electroencephalography (EEG) is a method to record an electrogram of the spontaneous electrical activity of the brain. The biosignals detected by EEG have been shown to represent the postsynaptic potentials of pyramidal neurons in the neocortex ...
(EEG), and frequently encountered in infants diagnosed with
infantile spasms
Epileptic spasms is an uncommon-to-rare epileptic disorder in infants, children and adults. One of the other names of the disorder, West syndrome, is in memory of the English physician, William James West (1793–1848), who first described it in ...
, although it can be found in other conditions such as
tuberous sclerosis.
Gibbs and Gibbs described hypsarrhythmia (originally spelled with one 'r') in 1952 as "...random high voltage waves and spikes. These spikes vary from moment to moment, both in time and in location. At time they appear to be focal, and a few seconds later they seem to originate from multiple foci. Occasionally the spike discharge becomes generalized, but it never appears as a rhythmically repetitive and highly organized pattern that could be confused with a discharge of the ''petit mal'' or ''petit mal'' variant type".
In most cases of infantile spasms, hypsarrhythmia either disappears or improves during a cluster of spasms and/or
REM sleep. Hypsarrhythmia rarely persists beyond the age of 24 months.
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Classification
Through the use of video EEG and continuous monitoring, five variants of the "classical" hypsarrhythmic pattern have been identified:
# Hypsarrhythmia with increased interhemispheric synchronization. Characterized by symmetric and synchronized activity, seen in patients with longstanding evolution, especially in those with West syndrome that changes to
Lennox-Gastaut syndrome.
# Asymmetric hypsarrhythmia. Associated with a brain structural abnormality, and does not necessarily predict the affected hemisphere.
# Hypsarrhythmia with a consistent focus of abnormal discharge.
# Hypsarrhythmia with episodes of voltage attenuation. Commonly seen during
nonrapid eye movement (NREM) sleep. When the episodes of voltage attenuation appear at the same time as an epileptic spasm does, they are called electrodecrements.
# Hypsarrhythmia with little spike or sharp activity.
The "H" in
PEHO syndrome stands for hypsarrhythmia.
Together with developmental regression and
infantile spasms
Epileptic spasms is an uncommon-to-rare epileptic disorder in infants, children and adults. One of the other names of the disorder, West syndrome, is in memory of the English physician, William James West (1793–1848), who first described it in ...
, hypsarrhythmia is one of the diagnostic criteria for
West syndrome
Epileptic spasms is an uncommon-to-rare epileptic disorder in infants, children and adults. One of the other names of the disorder, West syndrome, is in memory of the English physician, William James West (1793–1848), who first described it in ...
.
References
External links
{{Seizures and epilepsy
Electroencephalography
Neurological disorders