Narcolepsy is a chronic neurological disorder that affects a person’s sleep-wake cycles. A person may need to have specialized sleep tests before they receive a diagnosis.
Narcolepsy can cause interrupted nighttime sleep, excessive daytime sleepiness, and uncontrollable urges to sleep. Some people with narcolepsy also experience cataplexy, a sudden loss of muscle tone during wakefulness.
Narcolepsy affects up to
This article explores how doctors diagnose narcolepsy. It outlines the main sleep tests involved, gives tips on how to prepare, and describes how doctors interpret the results. Finally, it gives advice about when to see a doctor.
A doctor first takes a detailed medical history. They ask about the symptoms and any medications that the person is taking. They also conduct a physical examination.
Major symptoms associated with narcolepsy include:
- fragmented nighttime sleep
- excessive daytime drowsiness or sleepiness
- an irresistible urge to sleep
- hypnagogic hallucinations, which happen as a person falls asleep
- sleep paralysis, a feeling of being conscious but unable to move during sleep
- cataplexy, which often occurs during strong emotions such as excitement or laughter
- sleep attacks, brief episodes of sleep during activities
The doctor also aims to rule out other neurological conditions that may be causing the person’s symptoms. Examples of these health issues include:
- Idiopathic hypersomnia: This is a medical term for excessive daytime sleepiness with an unknown cause.
- Sleep apnea: This sleep disorder involves breathing repeatedly stopping and starting.
- Psychiatric disorders: Depression and bipolar disorder may cause lethargy, fatigue, and excessive sleepiness.
- Brain conditions: Brain injuries and brain tumors may cause excessive sleepiness.
- Kleine-Levin syndrome: This disorder causes excessive sleep, excessive hunger, and behavioral changes.
- Substance use: Substances such as alcohol, opioids, and benzodiazepines may cause excessive sleepiness.
If the doctor rules out these and similar health issues and makes an initial diagnosis of narcolepsy, they refer the person to a sleep specialist for further evaluation.
Sleep specialists may conduct these two sleep studies to help determine whether a person has narcolepsy:
Polysomnography
Polysomnography (PSG) is an overnight test. A person wears electrodes on their scalp, eyelids, and chin. These measure and record their brain activity, eye movements, and muscle tone while they sleep.
A doctor also monitors the person’s heart rate and breathing.
PSG can help determine:
- sleep duration
- sleep quality
- the stage in the sleep cycle at which rapid eye movement (REM) sleep occurs
PSG can also help detect other sleep disorders, such as sleep apnea and periodic limb movement disorder.
Multiple sleep latency test
The multiple sleep latency test (MSLT) typically occurs the day after PSG. It helps doctors identify whether the previous night’s sleep has an effect on daytime naps.
The MSLT involves taking five short naps over the course of the day, each separated by 2 hours. The test helps identify sleep patterns, including how quickly the person falls asleep and enters REM sleep.
Doctors typically ask a person to stabilize their sleep schedule a week before their sleep tests. They may also ask the person to keep a sleep diary and wear a device called an actigraph that monitors periods of rest and activity.
A doctor may ask a person to stop taking certain medications 1–2 weeks before the sleep tests. But a person should not stop taking any medications unless their doctor recommends it.
The doctor may recommend stopping treatments that can affect the brain, such as:
- antidepressants
- stimulants
- opioids
A person’s medical team will give them specific instructions about how to prepare for the test and what to expect.
Both PSG and an MSLT can take place in a hospital or a specialized sleep facility. PSG can also take place at home.
When deciding whether the person’s situation meets the criteria for narcolepsy, a sleep specialist considers the person’s symptoms and their PSG and MSLT results.
There are two types of narcolepsy. They work and progress in different ways:
- Narcolepsy type 1: This involves cataplexy and is associated with low levels of a chemical messenger in the brain called hypocretin-1 or orexin-A. It regulates arousal, wakefulness, and appetite.
- Narcolepsy type 2: This does not involve cataplexy and is associated with normal or unknown levels of orexin-A.
These methods may also help a doctor diagnose narcolepsy:
- Sleep history: The sleep specialist will take a detailed sleep history, including questions about sleep quantity and quality. Adults may need to complete a questionnaire called the Epworth sleepiness scale. Children ages 7–16 years may need to complete the Epworth Sleepiness Scale for Children and Adolescents.
- Pediatric daytime sleepiness scale: This measures daytime sleepiness in young children. It includes questions about the child’s level of drowsiness in a variety of settings.
- Sleep diary: A doctor may aska person to record their sleep patterns in a diary for 1–2 weeks. This includes recording the duration and quality of sleep and any symptoms, such as daytime sleepiness or sleep attacks.
- Actigraph: A doctor may ask a person to wear this device, which detects limb movements to analyze whether the person is active or asleep.
- Lumbar puncture or spinal tap: A doctor may ask for a sample spinal fluid to assess levels of orexin-A. Low levels
may help them diagnose narcolepsy type 1. - Genetic testing: A 2018 meta-analysis found that a certain protein increases a person’s risk of narcolepsy type 1 and, to a lesser degree, type 2. Still, this does not confirm the presence of either disorder.
- Blood work and imaging tests: A doctor may request these tests to rule out other conditions that can cause similar symptoms.
Narcolepsy can significantly affect a person’s quality of life, and it can be dangerous in certain situations.
The condition may remain undiagnosed for several years. It is important to see a doctor about any of these symptoms:
- excessive need to sleep
- inability to remain awake in situations where a person should be able to do so
- sudden loss of muscle tone in response to strong emotions, such as laughter or anger
It is vital that a person with these symptoms does not drive, operate heavy machinery, or take part in other potentially dangerous activities.
Narcolepsy is a chronic neurological disorder that changes the brain’s ability to regulate the sleep-wake cycle.
This can lead to a range of symptoms, including excessive daytime sleepiness and sleep attacks. In some people, narcolepsy causes a sudden loss of muscle tone in response to strong emotions.
Before the doctor diagnoses narcolepsy, a person needs to undergo two sleep studies in a hospital or specialized sleep center. Other tests may be necessary to rule out health issues that can cause similar symptoms.
Narcolepsy can significantly reduce the quality of life, and it can be dangerous in some situations. Anyone with symptoms of narcolepsy should consult a doctor as soon as possible. In the meantime, avoid driving and operating heavy machinery.