Lecture on Sleep Stages, Physiology, and Pathology

Introduction

• Overview of sleep stages and EEG waveforms.
• Discussion on normal sleep physiology.
• Conclusion with sleep pathology and mnemonics.

Stages of Sleep and EEG Waveforms

Awake Conscious State

• Types:
  • Alert: Beta waves.
  • Tired: Alpha waves.
• Mnemonics:
  • Beta waves for alertness (busting out work).
  • Alpha waves for tiredness (about to fall asleep).

Sleep Stages

• Non-REM (NREM) Sleep:
  • N1:
    - Theta waves.
    - Lightest sleep stage.
    - Features: Sudden myoclonic jerks.
    - Mnemonic: Replace “ni” in myoclonic with “n1”.
  • N2:
    - K complexes and sleep spindles.
    - Features: Bruxism (teeth grinding).
    - Mnemonic: “Bruxism” as “K” and “2 S’s” for sleep spindles.
  • N3:
    - Delta waves.
    - Deepest sleep stage.
    - Features: Sleepwalking, night terrors, bed wetting.
• REM Sleep:
  • Beta waves (paradoxical sleep).
  • Features: Rapid Eye Movement, atonia, increased heart rate, penile tumescence.
• PGO refers to Ponto-Geniculo-Occipital waves. These are specific electrical brain wave patterns observed during REM (Rapid Eye Movement)
• • Mnemonic: Beta waves and “boners” (B-B).

Normal Sleep Physiology

Sleep Stage Breakdown

• Awake Alert/Tired:
  • Memorize beta and alpha waves.
• N1:
  • 5-10% of total sleep time.
  • Features: Sudden myoclonic jerks.
• N2:
  • 50% of total sleep time.
  • Features: Bruxism.
• N3:
  • 10-20% of total sleep time.
  • Deepest sleep.
• REM:
  • 15% of total sleep time.
  • Features: Beta waves, eye movements, elevated autonomics.penile tumescence

Abnormal Sleep Pathology

Pathologies by Stage

• N1: Affected by obstructive sleep apnea. Increases N1 sleep.
• N2: Bruxism.
• N3: Sleepwalking, night terrors, bed wetting.
• REM:
  • Affected by Major Depressive Disorder (MDD).
  • Decreased REM latency, increased duration and density.

Narcolepsy

• Cause: Deficiency of orexin-producing neurons.
• Symptoms: Sudden cataplexy, daytime sleepiness.
• Diagnosis: Decreased orexin/hypocretin 1 in cerebrospinal fluid.
• Treatment: Modafinil, and SSRIs or SNRIs for hallucinations.

Epileptiform

• What it means: “Epilepsy-like” — looks like a seizure might happen or has happened.
• Looks like: Sharp, spiky, or jagged waves that suddenly appear.
• When seen: Can appear during a seizure (ictal) or in between seizures (interictal).
• What it suggests: The brain has abnormal electrical activity — often seen in epilepsy.

2.

Interictal

• What it means: “Between seizures.”
• Looks like: Similar to epileptiform activity — sharp spikes or waves — but happening when there’s no seizure.
• When seen: Patient is conscious and appears normal, but the EEG shows unusual activity.
• What it suggests: The brain is prone to seizures, even if one isn’t happening at that moment.

3.

Paroxysmal

• What it means: “Sudden and short burst.”
• Looks like: A wave or group of waves that suddenly appear, stand out, then disappear quickly.
• When seen: Can happen in normal sleep or in abnormal brain activity (like epilepsy).
• What it suggests: Sudden change in brain activity — could be normal or abnormal depending on the situation.

4.

Polyphasic

• What it means: “Many phases” (the wave crosses the middle line multiple times).
• Looks like: A complex wave that wiggles up and down more than once — like a squiggle with multiple peaks and dips.
• When seen: In some normal sleep patterns, and sometimes in seizure activity.
• What it suggests: The wave has a complex shape. Alone, it doesn’t mean epilepsy, but is seen in certain EEG patterns.

5.

Transient

• What it means: “Temporary” — lasts for a very short time.
• Looks like: A quick, isolated wave or group of waves that don’t repeat.
• When seen: Can be normal (like a K-complex in sleep), or abnormal.
• What it suggests: Something brief happened — not always dangerous.
• Sharp Transient is a brief, sharply contoured abnormal waveform seen on the EEG, often associated with epileptiform activity or seizures.

6.

Ictal

(Possibly what you meant by “Isetal”)

• What it means: “During a seizure.”
• Looks like: A rhythm that builds up and changes over time — like waves getting faster or bigger.
• When seen: While the patient is actively having a seizure.
• What it suggests: This is the actual seizure activity.

7.

Irregular Activity

• What it means: No clear rhythm or pattern.
• Looks like: Disorganized waves that don’t repeat consistently.
• When seen: Can be normal (like in drowsiness or sleep) or abnormal depending on context.
• What it suggests: The brain isn’t following a normal rhythm — may or may not be serious.

Conclusion

• Comprehensive overview of sleep stages and related pathologies.
• Importance of mnemonics for memorization.
• Encouragement to study further and connect with educational resources.