Narcolepsy

Prevalence

  • Narcolepsy-cataplexy affects 0.02%-0.04% of the general population in most countries.

  • Narcolepsy affects both genders, with possibly a slight male preponderance.

Risk factors

Environmental

  • Group A streptococcal throat infection, influenza (notably pandemic HlNl 2009), or other winter infections are likely triggers of the autoimmune process, producing narcolepsy a few months later.

  • Head trauma and abrupt changes in sleep-wake patterns (e.g., job changes, stress) may be additional triggers.

Temperamental

  • Parasomnias, such as sleepwalking, bruxism, REM sleep behavior disorder, and enuresis, may be more common in individuals who develop narcolepsy.

  • Individuals commonly report that they need more sleep than other family members.

Symptoms

  • Recurrent periods of an irrepressible need to sleep, lapsing into sleep, or napping occurring within the same day. These must have been occurring at least three 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:

a. 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.

b. 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 cerebrospinal fluid (CSF) hypocretin-1 immunoreactivity values.

a. Less than or equal to one-third of values obtained in healthy subjects tested using the same assay, or less than or equal to 110 pg/mL.

b. Low CSF levels of hypocretin-1 must not be observed in the context of acute brain injury, inflammation, or infection.


  • Nocturnal sleep polysomnography showing rapid eye movement (REM) sleep latency less than or equal to 15 minutes, or a multiple sleep latency test showing a mean sleep latency less than or equal to 8 minutes and two or more sleep-onset REM periods.