Narcolepsy affects the brain’s ability to regulate sleep-wake cycles, which can lead to a lack of alertness. Typically, narcolepsy does not show up on brain scans, so doctors diagnose it with sleep tests.

Narcolepsy is a chronic neurological condition that causes extreme daytime sleepiness.

In a usual sleep cycle, a person enters rapid eye movement (REM) sleep after about 60–90 minutes. However, people with narcolepsy enter REM sleep within 15 minutes of falling asleep.

This article examines the effects of narcolepsy on the brain and common symptoms. It also compares the differences between a typical brain and a brain with narcolepsy and whether narcolepsy shows up on a brain scan.

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Narcolepsy affects a person’s brain and actions in different ways.

Lack of sleep-wake regulation

Narcolepsy is a long-term brain condition. In some cases, it occurs due to a lack of the brain chemical hypocretin. This chemical helps sustain alertness and prevent sleep from occurring at the wrong times.

The lack of hypocretin causes extreme sleepiness and a lack of control of REM sleep. As a result, the paralysis or dreaming that usually occurs in REM sleep may overlap with wakefulness, causing dreamlike hallucinations.

Narcolepsy affects the brain’s ability to control sleep-wake cycles, so the brain cannot regulate when a person is asleep or awake.

It is important to note that the lack of hypocretin does not account for all cases of narcolepsy, as the exact causes often remain unclear.

Lack of alertness and wakefulness

During usual wakefulness, hypocretin sends signals that increase activity in the neurons essential for sustaining alertness and wakefulness.

In narcolepsy, the loss of hypocretin may cause reduced or inconsistent activity in these neurons. As a result, people with narcolepsy can be fully alert at times but find it difficult to sustain alertness for long periods.

Activation of emotions and lack of muscle tone

Cataplexy and sleep paralysis are atypical states where the brain circuits that produce paralysis during REM sleep become active during wakefulness.

Research continues to explore how positive emotions may trigger cataplexy. The amygdala and prefrontal cortex are brain regions that regulate emotional responses. Neurons in these regions are active during cataplexy.

There are two types of narcolepsy: narcolepsy type 1 (with cataplexy) and narcolepsy type 2 (without cataplexy).

According to the National Institute of Neurological Disorders and Stroke (NINDS), the most common symptoms of narcolepsy include:

  • Excessive daytime sleepiness (EDS): All people with narcolepsy have EDS. EDS causes persistent sleepiness and may cause a person to fall asleep suddenly during the day regardless of how much they slept at night.
  • Cataplexy: This may occur in some people and cause a sudden loss of muscle tone during wakefulness. This leads to weakness and a loss of voluntary muscle control. Cataplexy symptoms range from mild to more severe attacks, which, in some cases, result in a total body collapse, but a person can remain fully conscious.
  • Sleep paralysis: This refers to the temporary inability to move or speak while falling asleep or waking up. As with cataplexy, people remain fully conscious. After episodes end, individuals rapidly recover their full capacity to move and speak.
  • Hallucinations: Some may experience very vivid images which may accompany sleep paralysis. They also usually occur when people are falling asleep or waking up.
  • Fragmented sleep and insomnia: While some of these symptoms have no relation to narcolepsy, some people may also experience:
    • difficulties staying asleep at night
    • insomnia
    • vivid dreaming
  • Automatic behaviors: Individuals with narcolepsy may experience temporary and very brief sleep episodes during an activity such as eating or talking. They will automatically continue the activity without conscious awareness of what they are doing.

The NINDS suggest that while narcolepsy is a long-term condition, it does not usually worsen as a person ages. Symptoms may improve slightly over time but will never disappear.

In most cases, narcolepsy does not show up on a brain scan. Doctors usually diagnose narcolepsy with sleep tests.

Findings from early research claim that routine MRIs do not help diagnose narcolepsy. However, magnetic resonance spectroscopy appears to indicate structural changes in the disorder that a cranial MRI cannot detect.

Typically, doctors can get adequate information from a thorough medical history and by using a polysomnogram, which refers to a night sleep test, and a mean sleep latency test, which involves a daytime napping test.

Read more about tests for narcolepsy.

Common questions to ask a doctor include:

  • How do I know I have narcolepsy?
  • Do other sleep disorders have similar symptoms to narcolepsy?
  • What are the symptoms of excessive daytime sleepiness?
  • What are the symptoms of cataplexy?
  • How do doctors diagnose narcolepsy?
  • What treatments are available for narcolepsy?
  • Is there a cure for narcolepsy?
  • Is narcolepsy very common?
  • Is narcolepsy genetic?
  • Are there support groups for narcolepsy?
  • How can I manage narcolepsy in my work life?

Narcolepsy is a long-term neurological and brain condition that affects the brain’s ability to regulate sleep-wake cycles.

People experience extreme daytime sleepiness, a lack of alertness and wakefulness, and other sleep dysfunctions and disorders.

Doctors do not use MRI to diagnose narcolepsy, but magnetic resonance spectroscopy has indicated structural changes in scans. Sleep tests usually help doctors correlate symptoms to narcolepsy.

Potential complications of narcolepsy include depression and anxiety, a higher body mass index, and overall effects on quality of life and daily routines.