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The Pathophysiology of Narcolepsy

In the majority of people living with narcolepsy, loss of hypocretin leads to sleep-wake state instability.^1-3

People living with narcolepsy experience frequent and unpredictable transitions between wakefulness, non-REM sleep, and REM sleep.^4,5 The boundaries between sleep-wake states also become unstable, allowing elements of one state to intrude into another.^4,6

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Etiology

Learn about possible causes of hypocretin neuron loss in narcolepsy.

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Find out »

Sleep-Wake State Instability

See how loss of hypocretin leads to unstable boundaries between sleep-wake states.

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Go deeper »

Manifestations

Understand signs and symptoms that reflect underlying sleep-wake state instability.

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Make the connection »

References

American Academy of Sleep Medicine. International Classification of Sleep Disorders. 3rd ed. Text Revision. American Academy of Sleep Medicine; 2023.
España RA, Scammell TE. Sleep neurobiology from a clinical perspective. Sleep. 2011;34(7):845-858.
Saper CB, Fuller PM, Pedersen NP, Lu J, Scammell TE. Sleep state switching. Neuron. 2010;68(6):1023-1042.
van der Heide A, Lammers GJ. Narcolepsy. In: Thorpy MJ, Billiard M, eds. Sleepiness: Causes, Consequences and Treatment. Cambridge, UK: Cambridge University Press; 2011:111-125.
Ahmed I, Thorpy M. Clinical features, diagnosis and treatment of narcolepsy. Clin Chest Med. 2010;31(2):371-381.
Broughton R, Valley V, Aguirre M, Roberts J, Suwalski W, Dunham W. Excessive daytime sleepiness and the pathophysiology of narcolepsy-cataplexy: a laboratory perspective. Sleep. 1986;9:205-215.

Performance of routine tasks without awareness.

Sudden and brief loss of muscle tone, often triggered by strong emotions or certain situations. Narcolepsy with cataplexy is known as narcolepsy type 1.

Complete collapse to the ground; nearly all skeletal muscles are involved.

Only certain muscle groups are involved.

Biological clock mechanism that regulates the 24-hour cycle in the physiological processes of living beings. It is controlled in part by the SCN in the hypothalamus and is affected by the daily light-dark cycle.

Frequent awakenings and inappropriate transitions between states of sleep and wakefulness during nighttime sleep.

The inability to stay awake and alert during the day.

A neurotransmitter in the brain that supports wakefulness.

Vivid, realistic, and sometimes frightening dream-like events that occur when falling asleep.

Also known as orexin. A neuropeptide that supports wakefulness and helps suppress non-REM sleep and REM sleep.

Primary brain region for regulating the timing of sleep-wake states.

Unintentionally falling asleep due to excessive daytime sleepiness. Also known as “sleep attacks.”

Brief, unintentional lapses into sleep or loss of awareness.

A validated objective measure of the tendency to fall asleep in quiet situations.

People living with narcolepsy type 1 have low levels of hypocretin.

Narcolepsy without cataplexy; the cause of narcolepsy type 2 is unknown.

A state of sleep characterized by slower-frequency, more synchronized neuronal activity and decreased muscle tone. Deep stages help to restore the body.

A multiparameter test that monitors physiologic signals during sleep; used as a diagnostic tool in sleep medicine.

A state of sleep characterized by fast-frequency, desynchronized activity on EEG, vivid dreams, and loss of muscle tone. Normally occurs 60-90 minutes after sleep onset. Also known as “paradoxical sleep.”

Brief loss of control of voluntary muscles with retained awareness at sleep-wake transitions.

An abnormal sleep phenomenon characterized by REM sleep occurrence within 15 minutes of sleep onset; may occur during nighttime sleep or daytime napping.

A group of neurons located in the hypothalamus that are essential for promoting non-REM sleep. These neurons project to all wake-promoting regions to inhibit wakefulness and promote non-REM sleep during the night.