RPSGT RPSGT Electroencephalography & Signal Interpretation 5

Question 1

POSTS (positive occipital sharp transients of sleep) are normal EEG variants seen during which stage?

Accepted Answer

N1 and N2 sleep

Answer

POSTS are normal, benign waveforms seen in N1 and N2 sleep, maximal over occipital regions, and should not be mistaken for pathology.

Question 2

The international 10-20 electrode placement system derives its name from the fact that electrodes are placed at intervals of:

Accepted Answer

10% and 20% of skull circumference distances

Answer

The 10-20 system spaces electrodes at 10% and 20% intervals of the total skull circumference measured in each plane.

Question 3

A patient's EEG shows continuous, diffuse high-amplitude delta activity throughout an entire overnight study. This pattern is most consistent with:

Accepted Answer

Severe encephalopathy or deep coma

Answer

Continuous diffuse delta without normal sleep architecture cycling suggests severe cerebral dysfunction such as encephalopathy or coma.

Question 4

Which filter setting in PSG is specifically used to reduce slow-moving artifacts such as sweat and movement?

Accepted Answer

Low-frequency filter (LFF) / High-pass filter

Answer

The low-frequency filter (high-pass filter) attenuates very slow frequencies, reducing sweat and movement artifacts that appear as slow undulations.

Question 5

K-complexes on EEG must have a total duration of at least:

Accepted Answer

0.5 seconds

Answer

By AASM definition, a K-complex is a well-delineated negative sharp wave followed by a positive component with total duration ≥0.5 seconds.

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