How Narcolepsy Is Diagnosed

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Narcolepsy is a chronic neurological condition that disrupts of the sleep-wake cycle. It’s most often associated with extreme daytime sleepiness, though it also can lead to other symptoms, including cataplexy, a sudden loss of muscle control due to strong emotional response.

While home-exams and online tools can help, and physical examination will rule out other neurological disorders, diagnosis is only confirmed following an evaluation at a specialized sleep clinic.

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There, two tests, the polysomnogram (PSG), which measures physiological activity while you sleep, and the multiple sleep latency test (MSLT), which tracks daytime sleepiness, can confirm the presence of narcolepsy.

In light of recent advances in the understanding of narcolepsy, other evaluations, including genetic testing and assessment of levels of hypocretin (a neurotransmitter associated with regulating sleep and wake cycles) are emerging as potentially helpful for diagnosis.

Self-Checks/At-Home Testing

The first steps in diagnosis for most narcoleptic patients involves observation and at-home assessment, often in consultation with your doctor. While the following steps, alone, won’t confirm presence of the condition, they’ll help start the process:

  • Keeping a sleep journal over a one-to-two-week period is often recommended if narcolepsy is suspected. You’ll be asked to track the duration and quality of sleep overnight, as well as any daytime sleep attacks. Not only is this a good record for your doctor, but it’ll also give you a sense of the scope and scale of your case.
  • Epworth Sleepiness Scale is a self-assessment available online that measures daytime sleepiness often associated with narcolepsy. This simple questionnaire, available from the Division of Sleep Medicine at Harvard Medical School, can’t provide definitive diagnosis, but it can help determine if you should seek out a sleep specialist.
  • Ullanlinna Narcolepsy Scale is another questionnaire that can help determine the possibility of narcolepsy with cataplexy, which is the most common type. However, it’s important to note that some narcoleptic people—those with what’s called “type 2 narcolepsy”—don’t experience that symptom.

Physical Examination

Initial evaluation for this condition involves a thorough assessment of medical history. Your doctor will ask you about your sleep habits and evaluate for cataplexy, daytime hallucinations, and other symptoms. They may also perform neurological tests to make sure other issues aren’t causing problems.  

Labs and Tests

Since the exact causes of narcolepsy are still unknown, clinical diagnosis is a multi-step procedure that involves ruling out other causes of sleep disorders. Here’s a quick breakdown of typical approaches.

Polysomnogram

Also known as a “sleep study,” in a polysomnogram examination, your muscular movements, breathing, eye movements, and brain activity are recorded while you sleep overnight. Basically, this test evaluates the quality of sleep you’re getting to rule out other disorders as causing the problems.

Multiple Sleep Latency Test

The day after PSG testing, the MSLT is applied; this is the most definitive and important test in narcolepsy diagnosis. Basically, you’ll be asked to take five short naps in a day, each separated by two hours. Those who consistently fall asleep within eight minutes are considered to have excessive daytime sleepiness.

People with narcolepsy experience a quicker than normal onset of rapid eye movement (REM) sleep—the stage that causes dreaming. Achieving this state within 15 minutes of falling asleep in at least two of the five naps, as well as during the PSG, is a sign of this condition.

Hypocretin 1 Level Measurement

A more recently established diagnostic tool involves measuring levels of the neurotransmitter hypocretin 1. A small sample of cerebrospinal fluid is taken using a lumbar puncture (also known as a “spinal tap”) and clinically tested. A smaller than normal amount of hypocretin 1, which regulates sleep and wake cycles, is a sign of narcolepsy with cataplexy.

Genetic Testing

While not conclusive, the presence of a certain genetic marker, HLA-DQB1*06:02, is closely linked to narcolepsy. This is a derivation of a gene that regulates sleep and wake cycles. Genetic testing helps doctors diagnose cases where symptoms are atypical.

Differential Diagnosis

As noted, the key to narcolepsy diagnosis often involves differentiating it from others. Quite a few conditions are similar, including the following.

Idiopathic Hypersomnia

Idiopathic hypersomnia is a rare chronic or acute condition in which episodes of extreme sleepiness arise due to no known cause. It differs from narcolepsy in that sufferers don’t feel refreshed after taking naps, and they don’t experience uncontrollable sleep attacks.

Also, cataplexy is not associated with this condition. In some cases, those with idiopathic hypersomnia require 10 or more hours of sleep at night to feel rested.

Sleep Apnea

Sleep apnea is a common disorder characterized by breathing difficulties and interruptions while asleep. Sleep apnea leads to interruptions during sleep, loud snoring, daytime drowsiness, irritability, and problems concentrating, among other symptoms.

Associated with obstructions in the body’s airways, this condition, if untreated, can lead to high blood pressure, irregular heartbeat, diabetes, stroke, and heart failure, among other issues.    

Kleine-Levin Syndrome

Those with this rare disorder experience hypersomnolence, a need to sleep up to 20 hours a day, and compulsive hyperphagia, which is an excessive need to eat, as well as other behavioral issues.

When awake, those with this condition experience confusion, irritability, apathy, and lethargy (lack of energy). Other symptoms of this condition mimic narcolepsy, as Kleine-Levin syndrome can also cause hallucinations.    

Other Conditions

Some other conditions can also mimic narcolepsy, including brain tumors, head trauma, psychosis, and arteriosclerosis (hardening of the arteries) in the brain. These conditions can lead to a similar kind of excessive daytime sleepiness experienced by people with narcolepsy.

A Word From Verywell

Unlike many other diseases or conditions, narcolepsy can be challenging to diagnose; its exact causes are still unknown, and its symptoms and severity can vary a great deal.

However, as doctors and researchers learn more about it, there’s no doubt that approaches to taking it on, including detecting the condition, are only getting better. With the right medical help, this often challenging condition can certainly be overcome.

Essential to that, however, is a proactive approach to getting the care you need. If you or a loved one suspects narcolepsy, don’t hesitate to call your doctor and get on the path towards better days ahead.

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  1. National Organization of Rare Disorders. Narcolepsy. Updated 2017.

  2. National Institute of Neurological Disorders and Stroke. Narcolepsy fact sheet. National Institutes of Health. Updated 2020.

  3. Division of Sleep Medicine Harvard University. Self-evaluation: narcolepsy. 2018.