How is stage I sleep defined on normal sleep EEG?

Updated: May 15, 2018
  • Author: Selim R Benbadis, MD; Chief Editor: Helmi L Lutsep, MD  more...
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Answer

Answer

Stage I sleep is also referred to as drowsiness or presleep and is the first or earliest stage of sleep. Representative EEG waveforms are shown in the images below.

The earliest indication of transition from wakeful The earliest indication of transition from wakefulness to stage I sleep (drowsiness) is shown here and usually consists of a combination of (1) drop out of alpha activity and (2) slow rolling eye movements.
Slow rolling (lateral) eye movements during stage Slow rolling (lateral) eye movements during stage I sleep. Like faster lateral eye movements, slow ones are best seen at the F7 and F8 electrodes, with the corneal positivity indicating the side of gaze.
On this transverse montage, typical vertex sharp t On this transverse montage, typical vertex sharp transients are seen. In contrast to K complexes, these are narrow (brief) and more focal, with a maximum negativity at the mid line (Cz and to a lesser degree Fz). These are seen in sleep stages I and II.
Vertex waves are focal sharp transients typically Vertex waves are focal sharp transients typically best seen on transverse montages (through the midline) and would be missed on this longitudinal bipolar montage if it did not include midline channels (Fz-Cz-Pz). Vertex waves are seen in sleep stages I and II.
Positive occipital sharp transients of sleep (POST Positive occipital sharp transients of sleep (POSTS) are seen in both occipital regions, with their typical characteristics contained in their name. They also have morphology classically described as "reverse check mark" and often occur in consecutive runs of several seconds, as shown here.

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