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Hypocretin (orexin) deficiency predicts severe objective excessive daytime sleepiness in narcolepsy with cataplexy
  1. C R Baumann,
  2. R Khatami,
  3. E Werth,
  4. C L Bassetti
  1. Department of Neurology, University Hospital, Zürich, Switzerland
  1. Correspondence to:
 Professor Claudio L Bassetti
 Department of Neurology, Universitätsspital Zürich, Frauenklinikstrasse 26, 8091 Zürich, Switzerland; claudio.bassetti{at}


Cerebrospinal fluid (CSF) hypocretin-1 deficiency is associated with definite (“clear cut”) cataplexy in patients with narcolepsy. The relationship between CSF hypocretin-1 levels and other narcoleptic symptoms (including excessive daytime sleepiness, EDS) is not properly understood.

In a consecutive series of 18 subjects with narcolepsy and definite cataplexy, patients with undetectable CSF hypocretin-1 (n = 12) were found to have significantly lower mean sleep latencies (p = 0.045) and a higher frequency of sleep onset REM periods (SOREMPs, p = 0.025) on multiple sleep latency test than patients (n = 6) with detectable levels. Conversely, Epworth sleepiness scale scores, the frequency of hallucinations/sleep paralysis, and the frequency and severity of cataplexy were similar in both groups.

These results suggest that hypocretin deficiency identifies a homogenous group of patients with narcolepsy characterised by the presence of definite cataplexy, severe EDS, and frequent SOREMPs.

  • CSF, cerebrospinal fluid
  • DH, detectable hypocretin
  • EDS, excessive daytime sleepiness
  • ESS, Epworth Sleepiness Scale
  • MSL, mean sleep latency
  • MSLT, multiple sleep latency test
  • PSG, polysomnography
  • SNS, Swiss narcolepsy scale
  • SOREMP, sleep onset REM period
  • SPAS, Sleep Propensity in Active Situations
  • UH, undetectable hypocretin
  • UNS, Ullanlinna Narcolepsy Scale
  • cataplexy
  • excessive daytime sleepiness
  • hypersomnia
  • hypocretin
  • orexin

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  • Competing interests: none declared