Neurosurgery notes/Other specialities/Neurology/Neurology general/Sleep

Sleep

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Neurology general
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Sleep stages
Sleep abnormalities

Sleep physiology

  • Sleep cycle is regulated by the circadian rhythm, which is driven by suprachiasmatic nucleus (SCN) of the hypothalamus. Circadian rhythm controls nocturnal release of ACTH, prolactin, melatonin, norepinephrine: SCN → norepinephrine release → pineal gland → ↑ melatonin. SCN is regulated by environment (eg, light).
  • Two stages:
    • Rapid-eye movement (REM)
    • Non-REM.
  • Alcohol, benzodiazepines, and barbiturates are associated with ↓ REM sleep and N3 sleep; norepinephrine also ↓ REM sleep.
  • Benzodiazepines are useful for night terrors and sleepwalking by ↓ N3 and REM sleep.

Circadian rhythms

  • Regulated by the suprachiasmatic nuclei (SCN).
    • Regulates
      • Other hypothalamic nuclei
      • Melatonin release from pineal gland
        • SCN → norepinephrine release → pineal gland → inc. melatonin
  • Sleep duration
      • Newborn
      16 to 20 hours a day
      Child
      10 to 12 hours a day
      Adult
      6.5 hours per day
  • Types of EEG
      • Term
      Description
      Alpha
      Frequency 8-13 Hz. Awake eye closed
      Delta
      Frequency < 4 Hz. Very deep sleep, infants and in patients with organic brain disease
      Beta
      Frequency 14-40 Hz. Awake eye opened
      Theta
      Frequency 4-8 Hz. Children or adults with brain disorders or during emotional stress
      Gamma
      Frequencies > 40 Hz
      Lambda
      Diphasic sharp transient occurring over the occipital regions of the head of waking subjects during visual exploration. The main component is positive relative to other areas. Time-locked to saccadic eye movement. Amplitude varies but is generally below 50 mV
      Fast
      Activity of frequency faster than alpha (i.e. beta and gamma activity)
      Slow
      Activity of frequency slower than alpha (i.e. theta and delta activity)
      Sharp
      A transient, clearly distinguished from background activity, with pointed peak at a conventional paper speed or time scale and duration of 70-200 ms
      Spike
      A transient, clearly distinguished from background activity, with pointed peak at a conventional paper speed or time scale and a duration from 20 to 70 ms