Narcolepsy

Question 1

What is the prevalence of narcolepsy?

Answer 1

0.05%

Question 2

What genes are associated with narcolepsy?

Answer 2

HLA - DRB1*1501

HLA DQB1* 0602

Question 3

What are the clinical features associated with narcolepsy?

Answer 3

• Cataplexy (not everyone will have this)- sudden collapse especially in emotional circumstances such as laughing or crying. The individual will appear to be asleep but will have a basic awareness of what is going on around them.
• Excessive daytime somnolence.
• Hypnagogic (at the onset of sleep) / hynopompic (when coming round from sleep) visual hallucinations.
• Sleep paralysis.

Question 4

How should narcolepsy be investigated?

Answer 4

1. Polysomnography
2. Multiple sleep latency test
3. Lumbar puncture (measure orexin levels in CSF)

Question 5

What is orexin?

Answer 5

A neuropeptide that controls wakefulness. Levels are low in narcoleptics

Question 6

How is narcolepsy treated?

Answer 6

• Modafinil (general stimulant to be taken in the morning and at lunchtime).
• Dexamphetamine (2nd line stimulant).
• Venlafaxine (for cataplexy) (serotonin reuptake inhibitor).
• Sodium Oxybate (Xyrem)(2nd line treatment for sleepiness and cataplexy).