Narcolepsy1 is a rare and lifelong neurological disorder that affects the brain’s ability to control the sleep–wake cycle. Narcolepsy is a complex disorder that is thought to have a genetic component, but the specific genetic causes are not yet fully understood.
People with narcolepsy experience excessive daytime sleepiness and difficulty staying awake during the day as well as disruptions in their normal sleep patterns at night.
The overall prevalence of narcolepsy is estimated to be around 0.02–0.05% of the general population.
Narcolepsy is a chronic neurologic disorder affecting the sleep-wake cycle in the brain. It is divided into two subtypes based on clinical presentation and referred to as type 1 and type 2.
Narcolepsy, first described in 1880, is characterized by excessive hypersomnolence, cataplexy, hypnagogic/hypnopompic hallucinations, sleep paralysis, automatic behaviors and sleep onset rapid-eye movement (REM) periods.
Cataplexy, defined as brief episodes of muscle atonia evoked by strong, mainly positive, emotions, is the pathognomonic symptom of NT1, while NT2 does not present with strictly defined cataplexy.
Up to 0%
of patients with narcolepsy have cataplexy (NT1)
0 to 50 per 100,000 people
Estimation for prevalence for NT1
0 to 34 per 100,000 people
Estimation for prevalence for NT2
Excessive Daytime Sleepiness (EDS) is described as a persistent sense of mental cloudiness (brain fog), lack of energy, or extreme exhaustion. It includes daytime sleep attacks that may occur with or without warning and may be uncontrollable, and persistent drowsiness, which can continue for prolonged periods of time. Microsleeps, or fleeting, involuntary moments of sleep that may intrude into the waking state, are also experienced as part of EDS for many people. Naps can help people with narcolepsy feel refreshed for a short period of time before EDS symptoms return.
Cataplexy, the second major symptom of narcolepsy, is nearly unique to the disease. It is a sudden loss of muscle tone, usually triggered by emotions such as laughter, surprise, fear, or anger. Cataplexy occurs while the person is awake and causes feelings of weakness and a loss of voluntary muscle control. Cataplexy may occur more often during times of stress or fatigue. Attacks can involve only a slight feeling of weakness in one part of the body (i.e. sagging facial muscles, nodding head, buckling knees, garbled speech, etc.) or an immediate and total full body collapse. Although someone suffering a severe cataplexy attack may appear unconscious, they are actually awake and alert. Attacks can last from a few seconds up to several minutes. Cataplexy is related to the loss of muscle tone usually associated with dreaming or REM sleep; as protection against acting out one’s dreams, muscles become immobile or paralyzed. In cataplexy, this protection is triggered inappropriately during wakefulness.
Disrupted or fragmented nighttime sleep is sleep disrupted by periods of wakefulness, vivid dreams, sleep talking, and movement. People with narcolepsy typically have no difficulty initially falling asleep.
Hypnagogic (during sleep onset) and hypnopompic (during waking) hallucinations are vivid, realistic, and often frightening dreams that occur on the edge of sleep and wakefulness.
Sleep paralysis is the temporary inability to move, occurring in the transition between sleepand wakefulness.
Diagnosis is often delayed, with the average time between the onset of symptoms and the diagnosis ranging from 8 to 22 years. On average, it takes 10 years from onset of symptoms to an official diagnosis of narcolepsy and visits to approximately six different specialists.
Prior to diagnosis, it is not uncommon for people to be misdiagnosed with other sleep disorders, depression, psychiatric conditions, Attention-Deficit / Hyperactivity Disorder (ADHD) and even epilepsy.
Screening tool. Epworth Sleepiness Scale (ESS).
The ESS is a self-administered questionnaire with 8 questions. Respondents are asked to rate, on a 4-point scale (0-3), their usual chances of dozing off or falling asleep while engaged in eight different activities. Most people engage in those activities at least occasionally, although not necessarily every day. The ESS score (the sum of 8 item scores, 0-3) can range from 0 to 24. The higher the ESS score, the higher that person’s average sleep propensity in daily life, or their ‘daytime sleepiness’.
Polysomnography (PSG): An overnight sleep study that records brain activity, eye movements, muscle activity, and breathing. It can reveal if REM sleep occurs early in the sleep cycle and rule out other sleep disorders.
Multiple Sleep Latency Test (MSLT): Performed the day after PSG, it involves five 20-minute nap opportunities spaced 2 hours apart. It measures how quickly a person falls asleep and if they enter REM sleep.
Actigraphy: A wrist-worn device that records sleep-wake patterns over 1-2 weeks, used to rule out insufficient sleep or circadian rhythm disorders.
Cerebrospinal Fluid Hypocretin-1 Test: A lumbar puncture to measure hypocretin-1 levels. Low levels indicate type 1 narcolepsy.
If your diagnosis confirms narcolepsy, your doctor or sleep specialist will discuss treatment with you. Treatment usually consists of medication and behavior changes. Most likely, treatment will not relieve all symptoms. It make take weeks or months to manage symptoms. Getting started on proper treatment can help to feel better and live a more normal life.
Glossary of abbreviations
References
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