W6L2 - Sleep Disorders

Question 1

Define Sleep Paralysis and what is it associated with?

Answer 1

Sleep Paralysis

• Temporary period of paralysis prior to falling asleep (hypnogogic) or waking from sleep (hypnopompic)
• During episodes individuals are able to hear and open their eyes but unable to move.
• Associated with:
  
  • Hallucinations
  • REM at sleep onset
  • Narcolepsy and familial inheritance (isolated or substance-induced)
  • Supine sleeping (on back)

Question 2

What are the 3 types of SP

Answer 2

Intruder:

• Threatening presence with other hallucinations (e.g., footsteps, voices, humanoid apparitions, and feeling as though being touched or grabbed)

Incubus:

• Breathing difficulties, feelings of suffocation, bodily pressure, pain, morbid thoughts of impending death

(Moderate correlation between Intruder and Incubus experiences as well as correlated with fear/terror)

Vestibular-Motor (V-M):

• Sensations of linear and angular acceleration, floating, flying or falling, autoscopy (out of body experiences, fictive motor movements ranging from arm movements to sitting up to leg movement as though walking

(V-M less related to Intruder/Incubus/Fear experience)

Question 3

Explain the link between SP and Fear. What are some explanations for the fear.

Answer 3

SP tend to result in fear

• Exposure to trauma (e.g., PTSD sufferers), heightened stress, poor sleep quality and anxiety symptoms can increase the incidence of SP

Explanations

• Fear can arise during episode due to suppression of respiratory movement
• May also be involvement from activation of amygdala and brain tries to resolve emotional response by creating a threat
• Disturbance of Sleep-Wake System

Question 4

Prevalence, onset and progression of SP

Answer 4

Prevalance

• Varying. 3% - 62%
• Isolated/Recurrent
• Prevalent in shift-work population

Onset

• Predominantly occurs in adolescents
• Median = 16, Common age range 13-18

Progression

• Decreases with age

Question 5

What are the 4 classic features of Narcolepsy

Answer 5

Narcolepsy

Mandatory:

• Excessive daytime sleepiness (EDS)

Typically present:

• Cataplexy (60-70%)
  
  • Sudden loss of muscle tone in response to emotional (positive) stimuli
  • Knee-jerk reflex reduced
• Hypnagogic or hypnopompic hallucinations (30-60%)
  
  • Pre or post-sleep
• Sleep paralysis (25-50%)

Question 6

What do narcolyptic symptoms represent?

Answer 6

REM sleep components intruding during wake

REM appears at sleep onset (and in MSLT)

REM Sleep Atonia (Muscle Paralysis)

• Cataplexy
• Sleep paralysis

Intrusion of Dreams

• Hallucination

Question 7

What is the prevalance and onset of Narcolypsy

Answer 7

Prevalence/Onset

• 0.02-0.05%. Huge cross-cultural variability
  
  • Israel - 0.002%
  • Japan - 0.18%
• Equally in males and females
• Onset in adolesence
  
  • Teens-20’s
  • Sometimes following an illness/vaccination indicating an auto-immune component.

Question 8

Explanation for Narcolypsy

Answer 8

Orexin signalling is altered in Narcolepsy

• Absent/very low orexin in most cases (Induce sleep)
• Possible receptor abnormality.

Question 9

Diagnosis: Narcolypsy

Answer 9

Diagnosis: Narcoypsy

• Abnormal immune function
  
  • HLA subtype
  • Immune system attacks orexin
• Sleep study
  
  • Short sleep onset latency (SOL)
  • Short REM latency
  • Increased wake
• Multiple Sleep Latency Test (MSLT)
  
  • Rapid sleep onset
  • REM onset

Question 10

Narcolepsy – Treatment

Answer 10

Treatment of Narcolepsy: Only can treat symptoms

• Excessive Daytime Sleepiness
  
  • Planned naps
  • CNS stimulants (dex-amphetamine, modafinil)
  • Sodium oxybate
    
    • Puts people to sleep fast
• Cataplexy
  
  • Antidepressants (clomipramine, fluoxetine)
  • Sodium oxybate
• Research attempts to find orexin receptor agonists.
  
  • Orexin can’t cross BBB so can’t give orexin pill

Question 11

What is REM Behaviour Disorder (RBD). What does it often precede.

Answer 11

RBD

• Loss of atonia in REM, resulting in dreams acting out
• Often precedes degenerative disease by many years (Parkinson’s, Lewy body dementia, multiple systems atrophy).

Question 12

Animal study: Mechanism of REM muscle atonia

Answer 12

Rats

• Lesion of sublateral dorsal (SLD) region resulted in REM sleep without atonia
• Injected tracer into this region and found projections through the pons and medulla to the spinal ventral horn (contain the alpha-motor neurons).

Question 13

Why do you still even get REM sleep with lesion of the SLD?

Answer 13

Two populations of SLD neurons:

• Flip flop switch
• Atonia.

In Human RBD, PPT/LDT involved too.