History and exam
Key diagnostic factors
common
excessive daytime sleepiness
In contrast to the excessive daytime sleepiness of other sleep disorders, the sleepiness of narcolepsy often improves temporarily after a short daytime nap, and there is a refractory period of about 1 to several hours before the next episode, during which the patient feels more functional.
cataplexy
Loss of muscle tone typically lasts 0.5 to 2 minutes, but can last up to 30 minutes. Consciousness is usually intact. Frequently triggered by emotional stimuli such as laughter, excitement, or anger.
hypnagogic/hypnopompic hallucinations
Probably intrusions of rapid eye movement sleep dreaming into wakefulness either at the beginning of the night or on awakening. Patients usually recall these sometimes frightening events.
sleep paralysis
Immobility may be accompanied by hypnopompic hallucinations or a feeling of suffocation and can be frightening.
Other diagnostic factors
common
chronic fatigue or tiredness
Patients may report low physical or mental energy, a frequent correlate of sleep disorders.
poor performance at work
Patients may report reduced capabilities including inattention and inability to sustain repetitive tasks, especially in a low-stimulus environment.
poor memory and concentration
Often reported, and may show progressive deterioration, frequently being attributed to aging.
car accidents
May be reported; due to sleepiness and overt dozing, especially in a low-stimulus situation.
slurred speech
May precede sleep attack.
blurred vision
May precede sleep attack.
irregular breathing pattern
May precede sleep attack.
sleep attacks
High propensity to fall asleep in inappropriate situations several times a day. This can take place during monotonous, sedentary activity, or postprandially, and when fully involved in a task.
fragmented nocturnal sleep
Can spontaneously awaken many times during the night, followed by difficulty returning to sleep.
symptoms of other sleep disorders
People with narcolepsy have a higher than expected incidence of other sleep disorders, such as obstructive sleep apnea, periodic limb movement disorder of sleep, and rapid eye movement (REM) sleep behavior disorder.[1][80][82]
Patients with narcolepsy have frequent sleep-onset REM sleep periods or REM intrusions into wakefulness. This may be elicited from the history as dreams during transitions from sleep to waking and vice versa, dreams during short daytime naps, and difficulty in differentiating such dream episodes from reality.
obesity
May contribute to obstructive sleep apnea. Obesity is also associated with Prader-Willi syndrome.
uncommon
status cataplecticus
Rare manifestation of cataplexy, characterized by prolonged cataplexy that lasts for hours.[5]
hepatomegaly
Associated with Niemann-Pick disease type C.
paresis
Associated with multiple sclerosis.
Risk factors
strong
low cerebrospinal fluid hypocretin
Deficiency is firmly established as a cause of narcolepsy type 1. Levels are normal in narcolepsy type 2.[1]
human leukocyte antigen (HLA)-DQB1*0602
Nearly all patients with narcolepsy test positive for the human leukocyte antigen (HLA) HLA-DQB1*0602 haplotype, including those without cataplexy but with hypocretin deficiency.[1]
linkage to 4p13-q21
Although usually sporadic, some familial cases have strong linkage to 4p13-q21. The genes underlying these familial cases are generally unknown, but 8 Japanese families with narcolepsy showed linkage to a site on chromosome 4p13-q21, which may act in concert with the HLA-signaled predisposition.[58]
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