What are the ICSD-3 classifications of narcolepsy and how are they diagnosed?

Updated: Sep 04, 2019
  • Author: Sagarika Nallu, MD; Chief Editor: Selim R Benbadis, MD  more...
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Answer

The American Academy of Sleep Medicine's International Classification of Sleep Disorders, Third Edition (ICSD-3) reclassified narcolepsy into two types (narcolepsy type 1 and narcolepsy type 2). [10, 11] In the previous edition of the manual, narcolepsy was categorized as either narcolepsy with cataplexy or narcolepsy without cataplexy. [12] The change in nomenclature reflects the fact that some patients demonstrate hypocretin deficiency (the fundamental cause of narcolepsy), but may not demonstrate cataplexy at the time of diagnosis although they may eventually.

Narcolepsy type 1 is distinguished by sleepiness plus cataplexy and a positive multiple sleep latency test (MSLT), or sleepiness plus hypocretin deficiency. Narcolepsy type 2 requires sleepiness and a positive MSLT and the absence of type-1 markers. And, the hypersomnia and/or MSLT findings must not be better explained by another sleep, neurologic, mental, or medical condition or by medicine or substance use. [10]

Whenever possible, the diagnosis of narcolepsy should be confirmed by polysomnography (PSG) followed by a multiple sleep latency test (MSLT); the MSLT should show sleep latency 8 minutes or less and 2 or more sleep-onset REM periods (SOREMPs). A SOREMP on PSG the night preceding the MSLT may replace one of the SOREMPs on the MSLT. This change in the SOREMP requirement means that clinicians need to pay closer attention to the early stage scoring of night PSGs. An alternative criterion for diagnosis is a CSF hypocretin level of 110 pg/mL or lower.


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