Positive Occipital Sharp Transients of Sleep (POSTS) and interictal epileptiform discharges (IEDs) are both EEG patterns, but they have distinct characteristics, clinical implications, and contexts.
Positive
Occipital Sharp Transients of Sleep (POSTS)
1.
Definition:
§ POSTS are
sharp waveforms that occur predominantly during sleep, particularly in
non-rapid eye movement (NREM) sleep.
2.
Waveform Characteristics:
§ They
typically exhibit a triangular shape and can be monophasic or diphasic. The
first phase usually has a higher amplitude than the second phase.
3.
Location:
§ Recorded
primarily from the occipital leads (O1 and O2) of the EEG, with a positive
field at the occiput. Phase reversals are often observed at these
electrodes.
4.
Duration and Frequency:
§ Each
transient lasts approximately 80 to 200 milliseconds and can occur in trains,
typically lasting about 1 to 2 seconds.
5.
Clinical Significance:
§ Generally
considered a normal variant in healthy individuals, especially in children and
adolescents. They are not associated with any pathological conditions and are
common in the EEGs of healthy adults.
6.
Age-Related Variability:
§ More
prevalent in younger populations and tend to decrease with age. Rarely observed
in individuals over 70 years old.
Interictal
Epileptiform Discharges (IEDs)
7.
Definition:
§ IEDs are
abnormal EEG patterns that occur between seizures in individuals with epilepsy.
They represent a transient abnormality in the brain's electrical activity.
8.
Waveform Characteristics:
§ IEDs can
vary in morphology but are often characterized by sharp waves or spikes. They
typically have a more asymmetric shape compared to POSTS and may show a sharper
contour.
9.
Location:
§ IEDs can
occur in various regions of the brain, depending on the type of epilepsy. They
are not limited to the occipital region and can be localized to specific areas
associated with seizure activity.
10.
Duration and Frequency:
§ IEDs are
usually brief, lasting less than 100 milliseconds, and can occur sporadically
or in bursts. They do not typically occur in trains like POSTS.
11. Clinical
Significance:
§ The
presence of IEDs is indicative of an underlying epileptic condition and may
correlate with seizure activity. They are considered abnormal findings and can
help in diagnosing epilepsy.
12. Age-Related
Variability:
§ IEDs can
occur in individuals of any age with epilepsy, but their presence and frequency
may vary based on the type of epilepsy and the individual's age.
Summary
In
summary, while both Positive Occipital Sharp Transients of Sleep and interictal
epileptiform discharges are observed in EEG recordings, they differ
significantly in their characteristics, clinical implications, and contexts.
POSTS are generally benign and associated with normal sleep activity, while
IEDs are abnormal findings indicative of epilepsy and potential seizure
activity. The identification of POSTS suggests normal sleep function, whereas
the presence of IEDs raises concerns about underlying neurological
conditions.
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