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What is narcolepsy?

Narcolepsy affects approximately 1 in every 2000 in the U.S. Narcolepsy is one of the sleep disorders classified as a Central Disorder of Hypersomnolence, as is Idiopathic Hypersomnia (IH). There are two types: Narcolepsy Type 1 (NT1) and Narcolepsy Type 2 (NT2). People with narcolepsy experience some of the same symptoms as people with IH.

Symptoms for NT1 and NT2

The most prevalent and frequent symptom is:

• Excessive daytime sleepiness (EDS) is characterized by persistent sleepiness, brain fog, and drowsiness. The severity of EDS for narcolepsy is measured by a subjective test called the Epworth Sleepiness Scale (ESS).

People with narcolepsy at varying frequencies may experience:

• Sleep paralysis is an inability to move at sleep-wake-transitions.

• Hypnagogic/hypnopompic sleep-related hallucinations are vivid audio, visual, and/or tactile events when falling asleep or awakening.

• Disturbed nighttime sleep is described as fragmented sleep with multiple awakenings.

NT1 distinguishes itself from NT2 in that it is characterized by:

• Cataplexy is a sudden muscle weakness triggered by emotion.

Some people with NT1 and NT2 also on occasion share the following symptoms with people with IH:

• Sleep Inertia or “sleep drunkenness” is a temporary sense of grogginess and disorientation upon waking up from sleep.

Diagnosis

The average time between the onset of symptoms and diagnosis is 7-10 years. Narcolepsy can only be diagnosed definitively with a set of sleep studies. Your doctor will take a medical history and perform a physical exam. Once other disorders causing sleepiness have been ruled out, diagnosis for NT1, NT2, and IH requires an overnight Polysomnogram (PSG) and a Multiple Sleep Latency Test (MSLT). Your doctor may also ask you to keep a sleep diary. If a sleep study is repeated, an NT2 diagnosis may change to an IH diagnosis, and similarly, an IH diagnosis may change to an NT2 diagnosis.

• PSG – takes place overnight in a sleep lab and monitors brain activity, heart rate, breathing, eye and leg movements, and oxygen.

• MSLT – occurs after a polysomnogram and gives you a nap opportunity approximately every 2 hours over the course of the day for a total of 4-5 naps. It records the time it takes for you to fall asleep during a nap and what sleep stages you enter.

There is another test, a lumbar puncture, which is infrequently used. This measures the level of orexin (also known as hypocretin) in your cerebrospinal fluid.

NT1 Etiology

Normal sleep is characterized by the following cycle: Non-Rapid Eye Movement 1 (NREM-1), NREM-2, NREM-3, and REM. It takes about 90 minutes to move through this cycle. Most people will have 4-5 cycles during the night. Orexin is a neurotransmitter that emits signals to regulate sleep cycles. Because NT1 is characterized by low levels of orexin, people with NT1 are unable to regulate their sleep/wake cycle and may go into REM sleep too early and have fragmented sleep throughout the night.

NT2 Etiology

The cause of NT2, as well as IH, is not yet known.

Treatment

Currently, medications are available to treat two narcolepsy symptoms: EDS and cataplexy. Some are FDA-approved and some may be prescribed off-label (not FDA-approved for treatment of specific narcolepsy symptoms). FDA-approved medications that are taken at night are known as the sodium oxybate class, which is a central nervous system depressant. One FDA-approved medication that is taken in the morning increases histamine in the brain, which is a wake-promoting neurotransmitter.

Most off-label medications only treat EDS and include traditional stimulants and wake-promoting agents. Antidepressants may also be prescribed off-label to specifically treat cataplexy symptoms, yet they have not been formally studied or approved by the FDA for this use.

Contacting a physician is an important step in determining an individualized treatment plan.

Clinical Research

A considerable amount of research is being conducted to advance new treatments for people with NT1, NT2, and IH. This research includes wake-promoting agents, and agents that address a loss of orexin in the brain, which occurs in NT1.