Overview: What is narcolepsy?
Narcolepsy is a neurological disorder in which sleep-wake regulation in the brain is disturbed. The result is excessive sleepiness during the day, which sufferers cannot resist and which cannot be alleviated even with sufficient sleep.
Two main forms of narcolepsy
Experts distinguish two main forms of narcolepsy, in terms of the symptom cataplexy (sudden slackening of muscles as a result of strong emotional stimuli) described below:
Narcolepsy type 1 is associated with such attacks of muscle flaccidity (cataplexies). This variant probably accounts for the majority of all cases of narcolepsy. In most cases, cataplexies are not present from the onset of the disease, but develop months to years after the initial symptom, daytime sleepiness. The decisive factor for narcolepsy type 1 is the fact that a measurable nerve messenger substance is largely missing in the cerebrospinal fluid (CSF), i.e. the producing nerve cells in the brain have been lost.
Without deficiency of this nerve messenger and without cataplexy, narcolepsy type 2 progresses. In certain cases, narcolepsy type 2 is only the early stage of type 1, i.e., over time, the affected person does develop cataplexies – the diagnosis then changes from “narcolepsy type 2” to “narcolepsy type 1”.
Narcolepsy – incidence and age
Narcolepsy is not all that rare. Research shows that in Europe, only 26 to 50 people out of 100,000 of the population suffer from it. However, experts assume that the number of unreported cases is high – many people probably suffer from narcolepsy without being aware of it or their doctor.
The disease can appear for the first time at almost any age. In most cases, however, narcolepsy begins at a younger age, during adolescence or before the age of 40. Both sexes are affected equally.
Narcolepsy: causes and risk factors
Narcolepsy is a well-studied neurological disorder. It is based on the loss of the predominant nerve cells in the brain that produce the nerve messenger hypocretin (or: orexin). This loss can be searched for and confirmed diagnostically by hypocretin measurements in the neural fluid; the measurement has been offered at the University Hospital Zurich since the early 2000s. Hypocretin is important for sleep-wake regulation: it strengthens wakefulness and stabilizes both wakefulness and sleep.
Experts suspect that the reason for hypocretin deficiency is an autoimmune reaction of the body, i.e. a dysregulation of the immune system. It is possible that in affected narcoleptics the immune system destroys those nerve cells that produce the hormone hypocretin. As a result, the normal sleep-wake rhythm is disturbed. Sufferers alternate frequently between sleeping and waking at night and during the day.
In addition to autoimmune processes, experts also discuss infections (such as with the flu) as triggers of narcolepsy. Very rarely there is a familial predisposition and also rarely the disease occurs as a symptom of brain damage – for example as a result of a stroke, encephalitis or an accident with brain injury. Researchers suspect that in these cases, a loss of hypocretin-producing neurons provides the impetus for the impaired sleep-wake regulation.
Any physical illness can also be associated with psychological stress. This can manifest itself in worry, tension, circling thoughts or sleep disturbances, among other things, and can complicate the course of treatment. If you or your relatives desire psychiatric-psychological counseling and support, our specialists at the USZ will be happy to assist you.
Narcolepsy is essentially characterized by the following symptoms:
- Daytime sleepiness: Narcoleptics are either constantly sleepy during the day or experience sudden attacks of falling asleep again and again – the sleepiness is so overpowering that they nod off, often only for a few minutes. If they (can) sleep for 15 to 30 minutes, they usually feel refreshd for a few hours afterwards before becoming sleepy again. Usually this daytime sleepiness becomes noticeable in monotonous situations (e.g. reading). However, some sufferers also tend to fall asleep in more active situations, such as while eating or driving.
- Cataplexy: This refers to the sudden, momentary loss of tension (tone) in the muscles of the face, arms, and legs, usually on both sides of the body simultaneously. Triggers are intense emotions such as laughter, joy, pride, surprise or anger. Cataplexy usually lasts only five to 120 seconds and can vary in severity. Sometimes the acute loss of tone is only noticeable by the fact that the facial muscles slacken briefly and the affected person speaks unclearly and slurred. But you can also buckle your knees briefly or even slump completely. In all cases, however, the affected persons remain fully conscious. When cataplexies occur, narcolepsy is almost always present. Conversely, not every narcoleptic has cataplexies (narcolepsy type 2).
- Hypnagogic hallucinations: The term refers to sensory illusions during the transition from waking to sleeping (i.e., during falling asleep) or from sleeping to waking (i.e., upon awakening). Some sufferers see or hear things that are not real. Tactile sensory illusions (supposed touches) are also possible.
- Sleep paralysis: During the phase of falling asleep and waking up, narcoleptics are sometimes temporarily unable to move or speak. Dream perceptions and waking consciousness can become mixed up here, so that the affected person does not know whether they are awake or asleep. You feel completely paralyzed for a short time. This feeling lasts only a few seconds to minutes and is not dangerous, but it can be very frightening.
- Disturbed night sleep: People with narcolepsy repeatedly wake up abruptly at night for no apparent reason. They are then immediately wide awake. These waking phases are usually short, but can also last longer.
Daytime sleepiness and cataplexy, as well as disturbed nighttime sleep, are considered core symptoms of narcolepsy type 1. Other symptoms such as sleep paralysis and hallucinations may also occur, but do not have to.
Concomitant diseases of narcolepsy
There are a number of conditions that are more common in narcoleptics than in people who do not suffer from it. These comorbidities include, for example, nightmares, sleepwalking, sleep-disordered breathing, migraines, obesity, and depression.
Narcolepsy – Diagnosis with us
If you experience unexplained sleepiness – possibly with bouts of muscle flaccidity – you should come to us. We will first ask you about your medical history(anamnesis). Describe as precisely as possible what complaints you have and how long they have existed. We may ask you specifically about the core symptoms of narcolepsy (daytime sleepiness and cataplexy). Also inform us if there are any known cases of narcolepsy in your family.
In the next step, we will examine you physically and take a blood sample. Sometimes severe fatigue and exhaustion can be explained by a deficiency of iron or vitamin B 12 or by impaired thyroid function. If other diseases are also possible causes, further examinations such as cardiac ECG or neurological tests can provide clarity.
If changes in the brain are suspected, imaging techniques such as magnetic resonance imaging are also used.
Before examinations in the sleep laboratory, we usually apply an actigraphy for 2 weeks. To do this, you wear a device on your wrist that looks like a wristwatch without a dial. This actigraphy device measures your movements and light over 2 weeks. From this, it can subsequently be deduced how your day-night and sleep-wake rhythm was. This can provide crucial diagnostic information and is important for the interpretation of measurements in the sleep laboratory. For example, if someone comes to the sleep lab after chronic sleep deprivation, it is quite understandable that the sleep pressure is very high in all measurements, without the need for a disease to be present.
Polysomnography is then performed to diagnose narcolepsy. You will spend the night in the sleep laboratory – under continuous monitoring of various bodily functions. Among other things, you are connected to equipment that monitors and measures your brain waves, heart and breathing activity. Cameras also record sleep and wake periods, as well as any arm and leg movements during sleep. This allows other causes of daytime sleepiness, such as sleep apnea syndrome or restless legs syndrome, to be detected or ruled out.
Multiple Sleep Latency Test (MSLT)
Indispensable after polysomnography is the Multiple Sleep Latency Test (MSLT), which is performed the following day. You may lie down in bed and fall asleep for 20 minutes four to five times at intervals of two hours. Your brain waves are measured via electrodes on your head (electroencephalography, EEG) to check after how many minutes you fall asleep and which sleep phase you enter.
Also helpful in clarifying sleep problems can be sleep diaries and sleep questionnaires, such as the Epworth Sleepiness Test. In the case of unclear symptoms or absence of cataplexies, an examination of the cerebrospinal fluid (CSF diagnostics) may be useful. The concentration of hypocretin is measured. It is decreased in narcolepsy type 1, but normal in narcolepsy type 2. Further day testing may be necessary when assessing the fitness to drive of motorized vehicles. Without appropriate evidence, a person with narcolepsy is not eligible to drive a motor vehicle.
In addition, many people with narcolepsy have a genetic trait (marker) in their blood, namely a specific histocompatibility antigen (HLA-DQB1*0602). A blood test for this HLA marker, if positive, may indicate narcolepsy. There are also many healthy people (about 30 percent) who have this HLA marker. It is therefore not suitable for making a diagnosis.
Narcolepsy: prevention, early detection, prognosis
There are no known measures to prevent narcolepsy. There is also no screening program for this rare disease. However, it is important that both the population and, above all, physicians are aware of this disease and recognize it in time.
Narcolepsy – course and prognosis
As mentioned above, pronounced daytime sleepiness is usually the first sign of the disease. In some sufferers it develops slowly over weeks to months, while in others it sets in within a few days. In narcolepsy type 1, seizures of sudden muscle flaccidity (cataplexies) also occur as the disease progresses. Depending on the individual case, other symptoms such as hallucinations may also occur.
The symptoms of narcolepsy can therefore vary greatly from person to person, and this also applies to the severity of the symptoms. For example, some people are only slightly affected by their narcolepsy in their daily lives, education and work, while others have to live with severe limitations. Some narcoleptics are even unable to work.
Regardless of its severity, the disease persists throughout life. This means that those affected usually also always have to take medication for the symptoms. Narcolepsy has no effect on life expectancy. However, pronounced daytime sleepiness increases the risk of accidents – for example in road traffic or burns in smokers.
Narcolepsy: Treatment is individual
The therapy of narcolepsy includes non-drug and drug measures. In doing so, we choose a treatment that suits the individual person concerned. The aim is to enable them to cope with their chronic illness as well as possible in the long term.
Non-drug therapy: What you can do yourself!
As a narcoleptic, you can do a lot yourself to ensure that your condition affects you as little as possible in your daily life. To do this, you should take to heart the following tips:
- Ensure a regular daily routine with short rest breaks – preferably at the same time every day. A short nap after lunch is indispensable. How many more rest breaks are advisable depends on the individual case. It is best to ask your doctor about this.
- Refrain from eating rich meals. These increase the tendency to fall asleep. Eat better in the course of the day several small meals.
- Avoid alcohol – it increases the tendency to fall asleep.
- You should also avoid nicotine. Smoking only seemingly keeps you awake – in the long run it increases the tendency to fall asleep.
- Milk and dairy products also increase the urge to fall asleep. Therefore, you should consume them preferably in the evening before going to bed.
- Caffeinated beverages can freshen you up a bit between scheduled rest breaks.
- If you tend to be overweight, you should incorporate regular exercise and physical training into your daily routine.
It is important that you accept your condition and learn how best to cope with it. Do not try to constantly fight against the annoying sleepiness and unwanted sleep attacks in everyday life – it will do no good and will only frustrate you.
Depending on the nature and severity of your symptoms, we will prescribe appropriate medication. Essentially, the following agents are available for symptomatic treatment of narcolepsy:
- Stimulants (psychostimulants) such as modafinil or methylphenidate are used to combat daytime sleepiness and unwanted attacks of falling asleep.
- For daytime sleepiness, cataplexies, disturbed nighttime sleep, sleep paralysis, and hypnagogic hallucinations, the primary remedy is sodium oxybate, a liquid taken immediately before sleep. As in the case of treatment with psychostimulants, a close connection to specialists and regular check-ups are indispensable.
- In cataplexies, tricyclic antidepressants such as clomipramine, reboxetine, or fluoxetine occasionally help.
For all medications, we will explain how to use them correctly, what to watch out for when taking them, and how to adjust the dose if needed. In addition, it may be useful for you to keep a diary of the dosage, effectiveness, and any side effects of the medications you take. This information can help you and us provide the best medication for your narcolepsy. Sleeping pills such as benzodiazepines or Z-drugs (e.g. zolpidem) should not be used to treat narcolepsy!