Narcolepsy

From Ganfyd

Narcolepsy is caused by deficient hypocretin transmission and is characterised by:

• Excessive day time sleepiness
• Abnormal REM sleep

The presence of cataplexy is diagnostic.^[1] Sleep paralysis which can occur in the majority of the population at some time or the other and may be disturbing to patients, may need to be distinguished from the rarer but often under diagnosed narcolepsy.

Aetiology

• Amimal models demonstrate key role hypocretin

Primary

• In man associated with decrease hypocretin-1 in CSF and decreased number hypocretin neurons in brain
• Most patients have HLA DQ?B1*0602 allele

Secondary

• Brain lesions due to tumour, multiple sclerosis, encephalitis etc affecting:
  • Posterior hypothalamus
  • Mesencephalon
  • Pons
• Newmann-Pick disease type-C
• Muscular dystrophy
• Parkinsons disease

Prevalence

• Suspected to be underdiagnosed - between 0.025 to 0.075 %
• More common in Japan

Features

• Bimodal onset with peaks around 15 years and 35 years
• Sleepiness
  • Irresistible
  • Short and reoccurring typically at 2 hour intervals with refreshed on recovery
  • Often patients recall dreaming
• Rapid eye movement manifestations
  • Cataplexy
  • Sleep paralysis
  • Hallucinations on sleep onset (hypnagogic hallucinations)

Differential diagnosis

• Sleep deprivation
• Sleep aponea
• Sleep paralysis
• Idiopathic hypersomnia
• Recurrent hypersomnia
• Epilepsy/Syncope
• Pseudonarcolepsy

Treatment

A full recent review^[2] commented that scheduled naps can help but only if supplemented by active therapy.

Sleepiness

• Modafinil^[3]
• Methylphenidate^[3]
• Amphetamines
• Sodium oxybate^[3]
• Mazindol
• Pemoline
• Selegiline

Cataplexy

See cataplexy for its treatment

Sleep pattern

• Sodium oxybate^[3]
• Benzodiazepines
• Zopiclone etc

References