Evaluating Patients for Narcolepsy

The American Academy of Sleep medicine (AASM) International Classification of Sleep Disorders - Third Edition (ICSD-3) contains diagnostic criteria for sleep disorders, including narcolepsy.

Narcolepsy type 1

• Excessive daytime sleepiness daily for ≥3 months^*
• One or both of the following:
  • Cataplexy and mean sleep latency ≤8 minutes and ≥2 SOREMPs on MSLT; SOREMP (≤15 min after sleep onset) on preceding nocturnal PSG may replace one of the SOREMPs on MSLT^†
  • Low or absent CSF hypocretin-1 levels^‡

Narcolepsy type 2

• Excessive daytime sleepiness and MSLT findings as above, but without cataplexy^§
• CSF hypocretin-1 levels are unknown or are above the threshold for narcolepsy type 1^§
• The hypersomnolence and/or MSLT findings are not better explained by other causes, such as insufficient sleep, OSA, delayed sleep phase disorder, or the effect of medications or substances or their withdrawal

Notes:

*In young children, narcolepsy may sometimes present as excessively long night sleep or as resumption of previously discontinued daytime napping.

†If narcolepsy type 1 is strongly suspected clinically, but MSLT criteria are not met, consider repeating the MSLT.

‡Low or absent CSF hypocretin-1 levels = CSF hypocretin-1 concentration measured by immunoreactivity is either ≤110 pg/mL or <1/3 of mean values in healthy subjects using the same assay.

§If cataplexy develops later or low or absent CSF hypocretin-1 levels are discovered, reclassify as narcolepsy type 1.

CSF, cerebrospinal fluid; ICSD, International Classification of Sleep Disorders; MSLT, multiple sleep latency test; PSG, polysomnography; SOREMP, sleep-onset REM period.

The American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) contains diagnostic criteria for sleep-wake disorders, including narcolepsy, designed for use by mental health and medical clinicians.

• Recurrent periods of an irrepressible need to sleep, lapsing into sleep, or napping occurring within the same day. These must have been occurring ≥3 times per week over the past 3 months
• The presence of at least one of the following:

1. Episodes of cataplexy, defined as either (a) or (b), occurring at least a few times per month:
   1. In individuals with long-standing disease, brief (seconds to minutes) episodes of sudden bilateral loss of muscle tone with maintained consciousness that are precipitated by laughter or joking
   2. In children or in individuals within 6 months of onset, spontaneous grimaces or jaw-opening episodes with tongue thrusting or a global hypotonia, without any obvious emotional triggers
2. Hypocretin deficiency, as measured using CSF hypocretin-1 immunoreactivity values (≤1/3 of values obtained in healthy subjects tested using the same assay, or ≤110 pg/mL). Low CSF levels of hypocretin-1 must not be observed in the context of acute brain injury, inflammation, or infection
3. Nocturnal sleep PSG showing REM sleep latency ≤15 minutes, or an MSLT showing a mean sleep latency ≤8 minutes and ≥2 SOREMPs

Notes:

DSM, Diagnostic and Statistical Manual of Mental Disorders.