Untreated narcolepsy can negatively affect many aspects of a person’s life. Treatment is available, but it is reliant on a successful diagnosis, which typically involves a battery of tests.

Narcolepsy is a rare and chronic condition in which the brain cannot properly regulate the sleep-wake cycle. The condition causes sudden and uncontrollable bouts of sleep and other types of sleep disturbances.

This article outlines the different tests for narcolepsy and answers some frequently asked questions about the condition. It also describes what narcolepsy is, who it affects, and why a person who experiences symptoms should undergo tests for the condition.

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Narcolepsy is difficult to diagnose. Part of the reason for this is that the symptoms are varied and can develop due to other conditions.

Before conducting tests for narcolepsy, a doctor will conduct a thorough physical exam and take a person’s medical history.

Common tests for narcolepsy include:

Epworth sleepiness scale (ESS)

Dr. Murray Johns developed the ESS in 1990 to assess “daytime sleepiness” in his patients.

The ESS is a questionnaire that requires a person to rate on a scale of 0–3 their likelihood of falling asleep while engaging in eight simple activities, which include reading and sitting in traffic.

If the questionnaire highlights an elevated level of sleepiness during waking hours, a person may go on to see a sleep specialist.

Polysomnography (PSG)

A PSG is a sleep study that requires an overnight stay in a sleep lab. The test measures different physiological factors to assess how quickly the person falls asleep and how soon they enter rapid eye movement (REM) sleep. REM is the deepest stage of sleep, and entering it too early in the sleep cycle can be a sign of narcolepsy.

Some physiological factors that the PSG measures include:

  • brain waves
  • eye movement
  • breathing
  • muscle tone

Multiple sleep latency test (MSLT)

The MSLT takes place in a sleep lab the day after the PSG test. For the MSLT, a person takes five short naps with 2-hour intervals, and a researcher measures how long it takes for the person to fall asleep and enter REM sleep.

A person may have narcolepsy if their average time to fall asleep is under 8 minutes, and they enter into REM sleep within 15 minutes on at least two occasions.

Hypocretin test

People with narcolepsy often have low levels of the neuropeptide hypocretin-1, which affects sleep-wake cycles.

In some cases, a doctor will recommend testing the levels of hypocretin-1. This is a rather invasive test that requires a lumbar puncture. However, a low level of hypocretin-1 is a very strong indicator of narcolepsy.

Narcolepsy is relatively rare, affecting an estimated 135,000–200,000 people in the United States. However, many more people may be living with narcolepsy without knowing it.

Although there is no cure for narcolepsy, it is important that those experiencing symptoms receive a test for the condition. A narcolepsy diagnosis can facilitate:

  • getting treatment and counseling to help manage the condition
  • requesting reasonable accommodations from an employer
  • avoiding the negative effects of narcolepsy on emotional health, education, career, and social life

Differential diagnosis

A differential diagnosis is a method of distinguishing a particular condition from other conditions with similar symptoms. A person who presents with narcolepsy symptoms will require narcolepsy testing to help with the differential diagnosis. This helps ensure that a person receives the correct treatment.

Some health conditions to rule out include:

Other examples include:

Narcolepsy is a chronic neurological disorder in which the brain does not regulate sleep-wake cycles as it should. The hallmark of the condition is excessive sleepiness, which does not relate to the amount of sleep a person gets. These bouts of sleepiness can be very sudden and overwhelming, and they may result in accidents or injuries.

Other symptoms of narcolepsy include:

  • Cataplexy: In this type of sudden muscle weakness, the muscles suddenly become limp, rendering a person unable to move. It often occurs when the person is experiencing strong emotions.
  • Sleep paralysis: In this temporary condition, a person is mentally aware but unable to move or speak when falling asleep or waking up. During such episodes, a person may experience sensory, auditory, or visual hallucinations.
  • Sleep disturbances: A person may have difficulty staying asleep, which may contribute to excessive sleepiness on waking.
  • Automatic behaviors: These are behaviors that a person carries out without conscious awareness. A person with narcolepsy may continue performing behaviors for a short time after falling asleep, and they may have no recollection of performing these behaviors at a later stage.

Following incidents of excessive sleepiness during waking hours or cataplexy, people with narcolepsy typically return to a normal level of consciousness fairly quickly.

Not everyone who has narcolepsy will exhibit all of the symptoms above. In fact, doctors can use the presence or absence of cataplexy to distinguish between type 1 narcolepsy and type 2 narcolepsy.

Narcolepsy affects about 1 in 2,000 people, although researchers believe that many more individuals may have this chronic condition but not have received the correct diagnosis.

Narcolepsy affects males and females approximately equally. According to the National Organization for Rare Disorders, medical experts have identified two peak periods for the onset of narcolepsy. These occur at about 15 and 36 years of age. However, the condition can develop at any age between childhood and 50 years.

Narcolepsy does not go away, but it is not a progressive disorder.

Below are some answers to questions that people often ask about narcolepsy.

What tests do doctors recommend for narcolepsy?

Tests for narcolepsy include ESS, PSG, MSLT, and the hypocretin test.

The PSG and MSLT tests are necessary for a narcolepsy diagnosis.

Can a blood test detect narcolepsy?

There are currently no blood tests for narcolepsy.

What symptoms indicate narcolepsy?

The key symptoms of narcolepsy include:

  • excessive sleepiness, which can include the rapid onset of overwhelming “sleep attacks”
  • cataplexy
  • sleep paralysis
  • hallucinations, particularly when falling asleep or waking up
  • disrupted sleep

Narcolepsy is a chronic condition in which the brain does not regulate sleep-wake cycles properly. It can cause cataplexy, sudden and overwhelming sleep attacks, disturbed sleep, and excessive sleepiness. Without treatment, narcolepsy can severely disrupt a person’s life.

Narcolepsy is difficult to diagnose, partly because the symptoms are similar to those of more common conditions. However, multiple tests are available to help doctors make a differential diagnosis. Based on the results of these tests, they can devise a suitable treatment plan.