Sleep Disorders

 

• DDx: Daytime sleepiness

  • Insomnia
  • Obstructive sleep apnoea.
  • Central sleep apnoea.
  • Night work
  • Drugs: hypnotics, β-blockers.
  • Parkinsonism
  • Hypothyroidism
  • Narcolepsy
  • Idiopathic hypersomnolence.

• Normal sleep physiology

  Overview:

  • Repeated 90 minute cycles of non-REM (NREM) followed by REM (rapid eye movement).
  • Cycles get longer through the night, and REM occupies a progressively greater share of the cycle.

  NREM phase, comprising 4 stages:

  • N1: transition from wake to sleep. 5% of total sleep, mainly at the start. May involve hypnic jerks. EEG: alpha waves of waking switch to wider theta waves.
  • N2: 50% of sleep. Sleep spindles on EEG.
  • N3+4 (aka deep, delta-wave, or slow-wave sleep): 20% of sleep. Involves voluntary muscle paralysis. Difficult to wake from. Shortens with age.

  REM phase:

  • 25% of total sleep.
  • Profound muscle paralysis, including of the accessory respiratory muscles, with only the diaphragm working.
  • However, there is autonomic activity, twitches and eye movement, and BP and HR changes.
  • Time when dreams mainly occur.

• Central sleep apnoea

  Aka nocturnal hypoventilation

  Definition

  An interruption of breathing during sleep, without an obstructive cause. Results from a compromise in chest wall function leading to loss of respiratory effort.

  Causes

  APNO2EIC:

  • Altitude
  • Primary central sleep apnoea (idiopathic).
  • Neuromuscular disease: muscular dystrophy (Duchenne's, myotonic dystrophy), MND.
  • Obesity hypoventilation syndrome (Pickwickian syndrome) and Opioids.
  • ↓Ejection fraction (heart failure).
  • Irregular spine: scoliosis.
  • CNS disease: brainstem lesions from stroke or congenital disease (congenital central hypoventilation syndrome, aka Ondine's curse).

  Presentation

  • Episodes of apnoea, often with a crescendo then decrescendo pattern. Worse during REM sleep.
  • Morning headache from ↑CO2.
  • Daytime sleepiness.
  • May be the presenting complaint of the underlying disease.

  Management

  Non-invasive ventilation.

• Insomnia

  Definition and epidemiology

  • Difficulty initiating or maintaining sleep resulting in distress or impaired function.
  • Prevalence: 1/3 in the UK. Commoner in women.

  Management

  Sleep hygiene:

  • Avoid caffeine after 12pm. Avoid alcohol just before sleep.
  • Regular bedtime, regular getting up time, and no daytime napping.
  • Regular exercise, but not just before sleep.
  • Use bedroom just for sleep and sex.
  • Avoid stimulation just before sleep: no bright screens, big meals, or exercise.

  CBT:

  • Individual or group.
  • Includes stimulus control – avoiding stimulants – and sleep restriction – only staying in bed for actual sleep time.

  Pharmacological treatment should be at lowest dose and for shortest time possible:

  • Melatonin: can be used for 3-10 weeks. Safe and effective.
  • Short-acting benzodiazepines and Z-drugs. Effective short term for severe and disabling crises (1-4 weeks), but should be avoided long-term due to dependency risk.
  • Sedating antihistamines. Only effective short-term.

• Nonbenzodiazepine hypnotics

  Z-drugs

  • Names: zopiclone, zolpidem, zaleplon.
  • Mechanism: like BZDs, positive modulators of GABAA receptor.
  • Just as addictive as BZDs.

  Others

  • Antihistamines: promethazine, diphenhydramine.
  • Melatonin: endogenous pineal hormone which aids sleep.

• Narcolepsy

  Pathophysiology and epidemiology

  • Loss of alerting neurons, namely those that produce hypocretin (aka orexin).
  • Onset in teens-20s.

  Signs and symptoms

  • Daytime sleepiness.
  • Cataplexy: ↓muscle tone due to emotion.
  • Sleep fragmented by irregular REM episodes and blurring of sleep/wake state, with hypnagogic hallucinations and sleep paralysis.

  Diagnosis

  • Clinical diagnosis.
  • Polysomnography may aid diagnosis.
  • MRI to exclude space-occupying lesions, and EEG to exclude epilepsy.

  Management

  • Patient education including sleep hygiene.
  • Modafinil for daytime sleepiness. 2nd line: methylphenidate.
  • Sodium oxybate for cataplexy. 2nd line: TCAs, SNRIs.
  • Contact DVLA. Can't drive until symptoms controlled.

• NREM parasomnias

  Definition

  • Parasomnias are abnormal behaviours associated with sleep.
  • In NREM parasomnia the patient becomes semi-awake but dissociated during slow wave sleep.

  Presentations

  • Confusional arousal i.e. awake but confused. Commoner in kids.
  • Night terror.
  • Sleepwalking
  • Sexsomnia
  • Sleep-related eating disorder.

• REM behaviour disorder

  • Loss of REM paralysis, leading to acting out dream content. A type of parasomnia.
  • Associated with Parkinson's disease and Lewy Body dementia.
  • Commonest in middle age to elderly males.