Sleep disorders are an important part of neurology examinations as they require a strong knowledge of complex diagnostic studies such as EEG, and also of a multitude of medications. In this chapter, you will learn sleep waveforms using real EEG tracings, and review high-yield treatments for sleep disorders. Test your knowledge at the end with practice questions and flashcards!
Authors: Jody Manners MD, Brian Hanrahan MD
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Table of Contents
Phases of Sleep
- Characterized by alpha frequency activities, sporadic eye movements, and a posteriorly dominant alpha rhythm that attenuates with eye-opening.
- Stage N1 (5%): Attenuation of the alpha rhythm, the emergence of theta activity, and slow rolling eye movements.
- Frontocentral beta activity can increase.
- Vertex waves and small sharp spikes can be seen.
- Young adults spend the least amount of time in NREM stage 1 sleep.
- Stage N2 (45-55%):
- The stage at which adults spend the most time during normal sleep.
- Characterized by the presence of either sleep spindles and/or K-complexes with theta range background activity.
- Positive Occipital Sharp Transients of Sleep (POSTS) are most prevalent in N2 but can also occur rarely in N1 and N3 sleep.
- Sleep spindles are thought to be generated by the reticular thalamic nucleus.
- Stage N3 (15-20%):
- a.k.a “deep sleep” or “slow-wave sleep” (no longer called “stage 4 sleep”)
- EEG will show slow-waves and high amplitude delta waves.
- Parasomnias tend to occur during this stage.
- Interictal EEGs can show anterior temporal spikes especially if the EEG is performed during non-rapid eye movement (NREM) sleep.
- 20-25% of sleep.
- Normally occurs ~90 minutes into sleep.
- Characterized by a desynchronized low voltage, high-frequency background.
- There will be decreased EMG activity (REM atonia).
- Sharply peaked irregular eye movements with lateral rectus spikes (see below) can be seen ON eeg. Note the lack of muscle artifact.