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.