Reviews

Narcolepsy: Diagnosis and management

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ABSTRACT

Narcolepsy is a chronic disorder of hypersomnia that can have a significant impact on quality of life and livelihood. However, with appropriate treatment, its symptoms are manageable, and a satisfying personal, social, and professional life can still be enjoyed. Greater awareness of the disorder promotes accurate and efficient diagnosis. With ongoing research into its underlying biology, better treatments for narcolepsy will inevitably become available.

KEY POINTS

  • Features of narcolepsy include daytime sleepiness, sleep attacks, cataplexy (in narcolepsy type 1), sleep paralysis, and sleep-related hallucinations.
  • People with narcolepsy feel sleepy and can fall asleep quickly, but they do not stay asleep for long. They go into rapid eye movement sleep soon after falling asleep. Total sleep time is normal, but sleep is fragmented.
  • Scheduled naps lasting 15 to 20 minutes can improve alertness. A consistent sleep schedule with good sleep hygiene is also important.
  • Modafinil, methylphenidate, and amphetamines are used to manage daytime sleepiness, and sodium oxybate and antidepressants are used for cataplexy.


 

References

Narcolepsy was originally described in the late 1800s by the French physician Jean-Baptiste-Edouard Gélineau, who reported the case of a wine merchant suffering from somnolence. In this first description, he coined the term narcolepsie by joining the Greek words narke (numbness or stupor) and lepsis (attack).1

Since then, the disorder has been further characterized, and some insight into its biological underpinnings has been established. Importantly, treatments have improved and expanded, facilitating its management and thereby improving quality of life for those with the disorder.

This review focuses on clinically relevant features of the disorder and proposes management strategies.

CLINICAL FEATURES

Narcolepsy is characterized by instability of sleep-wake transitions.

Daytime sleepiness

Clinically, narcolepsy manifests with excessive daytime sleepiness that can be personally and socially disabling. Cataplexy, sleep paralysis, and hypnagogic or hypnopompic hallucinations can also be present,2,3 but they are not necessary for diagnosis. In fact, a minority of patients with narcolepsy have all these symptoms.4 Narcolepsy is divided into type 1 (with cataplexy) and type 2 (without cataplexy).2

Sleepiness tends to be worse with inactivity, and sleep can often be irresistible. Sleep attacks can come on suddenly and may be brief enough to manifest as a lapse in consciousness.

Short naps tend to be refreshing. Rapid eye movement (REM) latency—the interval between falling asleep and the onset of the REM sleep—is short in narcolepsy, and since the REM stage is when dreaming occurs, naps often include dreaming. Therefore, when taking a history, it is worthwhile to ask patients whether they dream during naps; a yes answer supports the diagnosis of narcolepsy.5

In children, sleepiness can manifest in reduced concentration and behavioral issues.6 Napping after age 5 or 6 is considered abnormal and may reflect pathologic sleepiness.7

Cataplexy

Cataplexy—transient muscle weakness triggered by emotion—is a specific feature of narcolepsy type 1. It often begins in the facial muscles and can manifest with slackening of the jaw or brief dropping of the head. However, episodes can be more dramatic and, if the trunk and limb muscles are affected, can result in collapsing to the ground.

Cataplexy usually has its onset at about the same time as the sleepiness associated with narcolepsy, but it can arise even years later.8 Episodes can last from a few seconds to 2 minutes. Consciousness is always preserved. A range of emotions can trigger cataplexy, but typically the emotion is a positive one such as laughter or excitement.9 Deep tendon reflexes disappear in cataplexy, so checking reflexes during a witnessed episode can be clinically valuable.2

Cataplexy can worsen with stress and insufficient sleep, occasionally with “status cataplecticus,” in which repeated, persistent episodes of cataplexy occur over several hours.8 Status cataplecticus can be spontaneous or an effect of withdrawal from anticataplectic medications.2

Cataplexy is thought to represent intrusion of REM sleep and its associated muscle atonia during wakefulness.

Sleep paralysis, hallucinations

Sleep paralysis and hallucinations are other features of narcolepsy that reflect this REM dissociation from sleep.

Sleep paralysis occurs most commonly upon awakening, but sometimes just before sleep onset. In most cases, it is manifested by inability to move the limbs or speak, lasting several seconds or, in rare cases, minutes at a time. Sleep paralysis can be associated with a sensation of fear or suffocation, especially when initially experienced.8

Hypnopompic hallucinations, occurring upon awakening, are more common than hypnagogic hallucinations, which are experienced before falling asleep. The hallucinations are often vivid and usually visual, although other types of hallucinations are possible. Unlike those that occur in psychotic disorders, the hallucinations tend to be associated with preserved insight that they are not real.10

Notably, both sleep paralysis and hallucinations are nonspecific symptoms that are common in the general population.8,11,12

Fragmented sleep

Although they are very sleepy, people with narcolepsy generally cannot stay asleep for very long. Their sleep tends to be extremely fragmented, and they often wake up several times a night.2

This sleep pattern reflects the inherent instability of sleep-wake transitions in narcolepsy. In fact, over a 24-hour period, adults with narcolepsy have a normal amount of sleep.13 In children, however, when narcolepsy first arises, the 24-hour sleep time can increase abruptly and can sometimes be associated with persistent cataplexy that can manifest as a clumsy gait.14

Weight gain, obstructive sleep apnea

Weight gain is common, particularly after symptom onset, and especially in children. As a result, obesity is a frequent comorbidity.15 Because obstructive sleep apnea can consequently develop, all patients with narcolepsy require screening for sleep-disordered breathing.

Other sleep disorders often accompany narcolepsy and are more common than in the general population.16 In a study incorporating both clinical and polysomnographic data of 100 patients with narcolepsy, insomnia was the most common comorbid sleep disorder, with a prevalence of 28%; others were REM sleep behavior disorder (24%), restless legs syndrome (24%), obstructive sleep apnea (21%), and non-REM parasomnias.17

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