Narcolepsy and Idiopathic Hypersomnia

The chronic neurological disorder of narcolepsy involves excessive daytime sleepiness, and is often associated with sleep paralysis, hallucinations and cataplexy.

Idiopathic Hypersomnia is a rare disorder with similar symptoms—and often involving daytime sleeps of 1 - 2 hours which generally are not refreshing.

Overview—What is Narcolepsy?

Narcolepsy is a chronic neurological disorder. All people with narcolepsy experience excessive drowsiness and often a lack of energy, combined with strong urges to nap which can occur any time during the day. Brief naps lasting 20 – 30 minutes may help people to feel rested and be alert for several hours.

Cataplexy—a sudden loss of muscle tone while conscious—is associated with narcolepsy, as is sleep paralysis—in which people are unable to feel or move a part of their body as they are waking up from sleep.


People with narcolepsy often experience other symptoms including broken sleep at night, sometimes due to excessive leg movements during sleep, visual or auditory hallucinations as they are going to sleep or waking from sleep (known as hypnogogic or hypnopompic hallucinations) and commonly, people with narcolepsy experience lucid dreams (dreams in which they are aware that they are having a dream!).  So, despite being tired and sleepy all day, patients with narcolepsy often have poor quality sleep at night.

What Causes Narcolepsy?

Narcolepsy is caused by a malfunction of the part of the brain which controls levels of alertness. Narcolepsy is related to lack of a brain chemical called hypocretin (also known as orexin). In some cases (but not all) it is an inherited condition.

During normal daytime hours people affected might fall asleep without warning—and rapidly enter Rapid Eye Movement (or REM) sleep. During daytime naps as well as during nighttime sleep, hallucinations, cataplexy and sleep paralysis may occur.

How Does Narcolepsy Affect People?

Narcolepsy’s onset may be sudden or gradual. Personal, school and working life is often affected by sleepiness, and there is often a misplaced social perception of laziness or lack of interest. Depression is sometimes associated with narcolepsy, and driving a car is only advisable while under medication.

How is Narcolepsy Treated?

While many of the symptoms may be controlled with medication, there is no cure for narcolepsy. Doctors prescribe wake promoting medication to assist with sleepiness, and antidepressant medications are often used to prevent cataplexy. Adapting lifestyle to accommodate the effects of narcolepsy is an important dimension to treatment.

Overview—What is Idiopathic Hypersomnia?

Idiopathic hypersomnia is poorly understood neurological disorder resulting in unrefreshing sleep despite an adequate amount of sleep and often profound daytime sleepiness. Some patients with Idiopathic hypersomnia sleep for more than 12 hours per night.  People with idiopathic hypersomnia often report a profound need to nap during the day, but often wake feeling unrefreshed.

What Causes Idiopathic Hypersomnia?

A rare disorder, idiopathic hypersomnia’s cause is not completely understood but relates to the parts of the brain that regulate sleep and wakefulness.

How Does Idiopathic Hypersomnia Affect People?

Usually starting in people aged under 30, idiopathic hypersomnia appears gradually, often over months or even years. The most striking symptoms that people have is chronic excessive daytime sleepiness, often with prolonged sleep at night and non-refreshing sleep. Patients often describe ‘sleep drunkeness’ on waking suddenly, often in response to an alarm, and for a few minutes they may be confused and irritable until they fully wake up or go back to sleep. Other symptoms can include a feeling of ‘Brain Fog’ while awake with impaired concentration and headaches.  The disorder may cause feelings of depression, and people may have great trouble studying or working. Often friends and family have difficulty understanding the illness. Sadly, for many patients with this disorder, the diagnosis is often delayed as the symptoms are attributed to insufficient sleep, depression and laziness.

How is Idiopathic Hypersomnia Treated?

There is no cure for idiopathic hypersomnia, but symptoms may be controlled at least partly with medication. Fortunately, in approximately 10-15% of cases, idiopathic hypersomnia resolves spontaneously without intervention. Several research projects are currently underway around the world investigating new medications that may be able to assist with idiopathic hypersomnia.

What is the Multiple Sleep Latency Test?

A multiple sleep latency test is a key tool for diagnosing and differentiating between narcolepsy and idiopathic hypersomnia. After a night-time sleep study, patients are given a 20 minute opportunity to attempt to nap every two hours throughout the day while their sleep is measured.

The test measures how long it takes you to fall asleep, and whether REM sleep is quickly entered. Falling asleep quickly and going quickly into REM sleep are likely to indicate narcolepsy, while falling asleep quickly but not entering REM sleep quickly are likely to indicate idiopathic hypersomnia.