What is narcolepsy?
Narcolepsy is a neurological disorder that affects
the control of sleep and wakefulness. People with narcolepsy experience
excessive daytime sleepiness and uncontrollable episodes of falling asleep
during the daytime despite adequate sleep. These sudden sleep "attacks" may
occur during any type of activity and at any time of the day.
Who gets narcolepsy?
Approximately 1 in every 2,000 Americans has
narcolepsy. The risk of developing narcolepsy is greater in first-degree
relatives (i.e., parents, siblings, offspring) of narcoleptics. Narcolepsy can
occur in people of all ages, but the first sign of daytime sleepiness typically
begins in the teenage years or twenties. In many cases, narcolepsy is
undiagnosed and, therefore, untreated.
What causes narcolepsy?
Scientists have discovered that animals and humans
with narcolepsy have a loss of a neuropeptide in the brain called hypocretin.
This deficiency blurs the boundaries between sleep and wakefulness, which
underlies many of the symptoms of narcolepsy. According to experts, it is likely
narcolepsy involves multiple factors that interact to cause neurological
dysfunction and REM sleep (a phase of the sleep cycle noted by "rapid eye
movements") disturbances.
What are the symptoms of narcolepsy?
Symptoms of narcolepsy include:
- Excessive daytime sleepiness (EDS) — Almost all patients with
narcolepsy experience this symptom. In general, EDS interferes with normal
activities (work, school, etc) on a daily basis, whether or not patients
have sufficient sleep at night. People with EDS report mental cloudiness, a
lack of energy and concentration, memory lapses, a depressed mood, or
extreme exhaustion.
- Cataplexy — This symptom consists of a sudden loss of muscle tone
that leads to feelings of weakness and a loss of voluntary muscle control.
The muscle tone is lost in reaction to strong emotions, such as laughter,
joking, surprise, or anger. Attacks can occur at any time during the waking
period. The severity of attacks ranges from a brief buckling of the knees or
slackness in the jaw to total paralysis with collapse. Cataplexy usually
lasts a few seconds to several minutes. The frequency of attacks varies from
a few in a lifetime to many per day. Cataplexy occurs in at least 60% of
people with narcolepsy.
- Disrupted nighttime sleep — This symptom occurs in 60% to 90%
of patients. Awakenings may be frequent but are generally brief, and the
patient is often unaware of their occurrence.
- Sleep paralysis — This symptom involves the temporary inability to
move or speak while falling asleep or waking up. There is often a sensation
of being unable to breathe, which can be frightening. Episodes of sleep
paralysis typically resolve in a few minutes and are experienced by
approximately 60% of narcoleptics.
- Hallucinations — Usually, these delusional experiences are vivid and
frequently are frightening. The hallucinations occur at sleep onset or upon
awakening. Examples include feelings of levitation and sensations of being
touched by a person or thing that is not real. Hallucinations of this sort
occur in approximately 60% of narcoleptic patients. The hallucinations are
called hypnagogic hallucinations when accompanying sleep onset and
hypnopompic hallucinations when occurring during awakening.
How is narcolepsy diagnosed?
The diagnosis of narcolepsy is made after
performing a detailed medical and sleep history, physical examination, and sleep
testing (which is performed in a sleep disorders centers).
Two tests that are considered essential in confirming
a diagnosis of narcolepsy are the polysomnogram (PSG) and the multiple sleep
latency test (MSLT). The PSG is an overnight test that takes continuous multiple
measurements while a patient is asleep to document abnormalities in the sleep
cycle. A PSG can help reveal abnormalities in REM sleep seen commonly in
narcoleptics and can eliminate the possibility that an individual’s symptoms
result from another condition. Most narcoleptics show disruptions in normal
sleep patterns with frequent awakenings.
The MSLT is performed during the day to measure a
person’s tendency to fall asleep and to determine whether isolated elements of
REM sleep intrude at inappropriate times during the waking hours. As part of the
test, an individual is asked to take five short naps, usually scheduled 2 hours
apart. Narcoleptics generally fall asleep with every opportunity. They also fall
asleep quickly into REM sleep, known as sleep-onset REM periods (SOREMPs).
Whenever possible, medications that reduce the amount of REM sleep, such as
wake-promoting agents and antidepressants, should be discontinued for at least 2
weeks before testing.
How is narcolepsy treated?
The treatment of narcolepsy is aimed at improving
alertness during the desired time of the day based on the individual’s needs and
lifestyle. People with narcolepsy should maximize the quality and quantity of
sleep by adhering to the following:
- Maintain a regular sleep-wake schedule
- Avoid intentional sleep loss, such as staying awake late on weekends
- Avoid alcohol and other central nervous system depressants
- Modify work and school schedules if possible, such as avoiding early
morning classes
- Take short naps (20-30 minutes) as needed to avoid unintentional sleep attacks
- Use modest amounts of caffeine to promote alertness as needed
- Operate motor vehicles and other heavy machinery with extreme caution
and only when approved by your doctor
In addition to these measures, wake-promoting
medications are often prescribed to improve daytime sleepiness. Examples include
modafinil (Provigil®), armodafinil (Nuvigil®),
methylphenidate (Ritalin®), and amphetamine agents. These medications
can produce side effects similar to that of caffeine, such as agitation,
nervousness, and palpitations. Wake-promoting agents are generally initiated at
a low dose and increased gradually as needed. Careful monitoring is required as
high blood pressure and heart arrhythmias have been reported. Sodium oxybate
(Xyrem®) is the only FDA-approved medication used to treat daytime sleepiness
and cataplexy in patients with narcolepsy.
Cataplexy, hypnogogic hallucinations, and sleep
paralysis have been treated traditionally with two classes of antidepressant
medications, which include the tricyclic antidepressants, such as protriptyline
(Vivactil®) and clomipramine (Anafranil®); and the
selective serotonin reuptake inhibitors (SSRIs) like fluoxetine (Prozac®)
and sertraline (Zoloft®). SSRIs generally have fewer side effects
than tricyclic antidepressants.
Narcolepsy can be a debilitating disorder that
interferes with one’s ability to function in all aspects of life, include at
school, home, on the job, and behind the wheel of a car. Teachers and bosses
often view narcoleptics as lazy and unmotivated. People with narcolepsy are at
increased risk for motor vehicle accidents, occupational hazards, and academic
underachievement. Therefore, prompt diagnosis and treatment is required. To
achieve the highest degree of alertness and daytime functioning, communication
with your healthcare professional is highly important.
References
Avidan, Alon Y; Zee, Phyllis C. Handbook of Sleep
Medicine. 1st edition. Philadephia: Lippincott Williams and Wilkins. May 2006.
Foldvary-Schaefer N. The Cleveland Clinic Guide to
Sleep Disorders. New York: Kaplan Publishing, 2009
Narcolepsy/Cataplexy. American Sleep Association.
www.sleepassociation.org/index.php?p=whatisnarcolepsy. Accessed June 8, 2010
Narcolepsy. American Academy of Sleep Medicine.
www.sleepeducation.com/Disorder.aspx?id=5. Accessed June 8, 2010
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