Narcolepsy (English spelling)

Japanese: ナルコレプシー（英語表記）Narcolepsy

What is the disease?

Narcolepsy causes unbearable daytime sleepiness and loss of strength in the whole body when laughing or being startled. Cataplexy ( Strength and strength ) , appearing as soon as I fall asleep Sleep paralysis ( Sadness ) Symptoms are similar to Sleep paralysis ( Swimming paralysis ) Or, due to a dream experience when falling asleep Hypnagogic hallucinations ( New population generation ) It is a chronic disease whose main symptoms are

The disease most often begins in teenagers and rarely in middle age or later, affecting approximately 1 in 1,000 to 3,000 people.

What is the cause?

The cause of this disease has not yet been clarified. When examining the white blood cell blood type (HLA) of people with this disease, it is found that there are many people with a certain type, so it is thought that some constitutional factor is related to the onset of the disease.

Recently, it has been discovered that a decrease in a brain substance called orexin is involved in the onset of this disease.

How symptoms manifest

Narcolepsy causes intolerable daytime sleepiness. This occurs every day, regardless of whether the person slept well the night before. The sleepiness lasts for about 20 minutes each time, and is characterized by the feeling of refreshment after waking up. However, after 1-2 hours, sleepiness returns. Even in stressful situations such as during an exam or interview, where sleepiness would not normally occur, a sleep attack may occur in which the person suddenly becomes sleepy and falls asleep.

Cataplexy is a sudden muscle weakness that is triggered by a large emotional change, such as being surprised, impressed, laughing, etc. Usually, recovery occurs within a few seconds.

Sleep paralysis is a condition in which the whole body becomes weak as one begins to fall asleep, and is experienced as sleep paralysis. The dreams one experiences as one falls asleep may also be experienced as hypnagogic hallucinations.

Testing and diagnosis

To objectively assess daytime sleepiness, Sleep latency ( Swimming pool ) The test is carried out. The patient lies down in an EEG room about every two hours, four or five times during the day, and the time it takes for the patient to fall asleep after darkness is turned off (sleep latency) is measured using electroencephalograms. The shorter the time it takes for a sleep pattern to appear on the EEG, the stronger the sleepiness is judged to be. If the average sleep latency is eight minutes or less, the patient is diagnosed with abnormal sleepiness.

Treatment methods

Treatment is centered on drug therapy. Psychostimulants are used to prevent daytime sleepiness. Recently, a drug called modafinil (Modiodal) is often used. This drug has a relatively long duration of action, and taking it once in the morning will keep it effective until around the evening. Compared to the previously available methylphenidate (Ritalin) and pemoline (Betamine), it is characterized by being milder and having fewer side effects.

If Modiodal is not effective enough, Ritalin or Betanamine can be added to it. Ritalin has a short duration of action (it is quickly metabolized and excreted from the body), so it must be taken twice a day, in the morning and afternoon.

Drugs that suppress REM sleep are used to treat cataplexy, hypnagogic hallucinations, and sleep paralysis. The most commonly used of these are antidepressants such as Anafranil and Tofranil.

As for lifestyle changes, it is important to get into the habit of taking a 20-minute nap during your break.

What to do if you notice an illness

Narcolepsy, if left undiagnosed, can be a symptom of falling asleep at work. Laziness ( raw ) People are often mistaken for being drowsy or unmotivated. Drowsiness can also be the cause of industrial and traffic accidents. Therefore, if you suspect you have drowsiness, it is important to see a specialist to confirm the diagnosis and start treatment early.

Makoto Uchiyama

Source: Houken “Sixth Edition Family Medicine Encyclopedia” Information about the Sixth Edition Family Medicine Encyclopedia

Japanese:

どんな病気か

　ナルコレプシーは、昼間の耐えがたい眠気や、笑ったりびっくりすると全身の力が抜けてしまう情動脱力発作(じょうどうだつりょくほっさ)、寝入りばなに現れる金縛(かなしば)りのような症状である睡眠麻痺(すいみんまひ)や、寝入りばなの夢体験による入眠時幻覚(にゅうみんじげんかく)を主な症状とする慢性疾患です。

　この病気は10代に発症する場合がほとんどで、中年期以降に発症することはまれです。およそ1000～3000人に1人の頻度でみられます。

原因は何か

　この病気の原因はまだ明らかにされていません。白血球の血液型（HLA）を調べると、この病気にかかっている人には特定のタイプが多いため、何らかの体質的要因が発症に関係していることが考えられています。

　最近、オレキシンという脳内物質の低下が、この病気の発症に関わっていることがわかってきました。

症状の現れ方

　ナルコレプシーでは、日中に耐えがたい眠気が現れます。これは前夜によく眠れたかどうかにかかわらず、毎日起こります。1回の居眠りはおおよそ20分くらいで、目覚めたあとにすっきりするのが特徴です。しかし、1～2時間するとまた眠気がおそってきます。普通なら眠気を催すはずのない試験中や面接中などの緊張した場面でも、急に眠気におそわれ眠ってしまう睡眠発作を起こすことがあります。

　情動脱力発作は、びっくりしたり、感激したり、笑ったりした時など情動の大きな変化をきっかけに、突然筋肉の力が抜ける発作です。通常は、数秒以内に回復します。

　睡眠麻痺は寝入りばなに全身の脱力が起こるもので、自覚的には金縛りとして体験されます。寝つき際の夢が、入眠時幻覚として体験されることもあります。

検査と診断

　昼間の眠気を客観的にとらえるためには、反復睡眠潜時(すいみんせんじ)検査が行われます。これは、昼間に4回ないし5回、約2時間おきに脳波検査室で横になり、暗くしてから眠るまでの時間（睡眠潜時）を脳波で調べるものです。脳波で睡眠のパターンが現れるまでの時間が短いほど、眠気が強いと判定されます。平均睡眠潜時が8分以下の場合、異常な眠気と診断されます。

治療の方法

　治療は薬物療法が中心です。日中の眠気を防ぐためには、精神刺激薬を用います。最近はモダフィニル（モディオダール）という薬が多く使われます。この薬は作用時間が比較的長く、朝に1回服用することで夕方ころまで効果があります。これまであったメチルフェニデート（リタリン）やペモリン（ベタナミン）と比べて、マイルドで副作用が少ないのが特徴です。

　モディオダールでは効果が十分でない場合、これにリタリンやベタナミンを追加して使用します。リタリンは作用時間が短い（早く代謝され体外に排泄される）ため、朝と昼の2回服用する必要があります。

　情動脱力発作、入眠時幻覚、睡眠麻痺などには、レム睡眠を抑える作用をもつ薬物が使われます。このなかでよく使われているのは、アナフラニール、トフラニールなどの抗うつ薬です。

　生活の工夫としては、休み時間に20分くらいの昼寝をとる習慣をつけることが大切です。