Stroke (Cerebrovascular disease)

Japanese: 脳卒中（脳血管障害） - のうそっちゅう（のうけっかんしょうがい）（英語表記）Stroke (Cerebrovascular disease)

What is a stroke?

The word "stroke" is a general term, not a medical term. The official term is "cerebrovascular disease." Fainting ( Quietly ) The "soto" in "to fall suddenly" means "suddenly," and "chu" means "to be hit" in the word "poisoning" (to be hit by poison), so stroke means that the patient is suddenly hit by something (to fall down) due to a brain disease.

This is a word that was introduced from China, but it appears in Japanese books from 760 A.D., which shows that this disease has a long history in Japan. It is also evidence that people had some understanding of the existence of a disease called stroke even before the development of modern medicine.

Classification of cerebrovascular disorders

cerebral infarction ( Noise ) , cerebral hemorrhage ( Dispatch ) , and subarachnoid hemorrhage are the three most common cerebrovascular disorders.

As shown in Figure 1, the blood vessels in the brain may be damaged by arteriosclerosis or by blood flowing from other parts of the body ( Obturator ( Warrior ) When the artery is blocked, blood flow is cut off. As a result, blood and the nutrients such as oxygen and glucose carried by the blood cannot reach the brain tissue beyond the artery, and the brain tissue dies, which is called a cerebral infarction.

On the other hand, many small lumps form in the thin blood vessels deep in the brain due to high blood pressure or aging, and when blood pressure rises suddenly, these can burst and enter the brain. Hematoma ( Review ) This is called cerebral hemorrhage, which occurs in the large blood vessels on the surface of the brain. Aneurysm ( Domyakuryu ) This causes the brain to split apart, and the three membranes that surround the brain (the outer membrane) form. Dura mater ( This is good ) , arachnoid membrane, Pia mater ( Many ) ), subarachnoid hemorrhage occurs when bleeding occurs between the arachnoid membrane and the pia mater (i.e., under the arachnoid membrane).

We'll explain each of these in more detail later.

Although stroke is one of the national diseases in Japan, the number of deaths from stroke is showing a tendency to decrease year by year. However, this is mainly due to the decrease in deaths from cerebral hemorrhage, while the number of deaths from cerebral infarction and subarachnoid hemorrhage has not decreased very much.

In fact, while the mortality rate has decreased, the incidence rate has not, so the number of patients actually being treated in hospitals is increasing.

A survey conducted in Japan on a certain day showed that of 1.48 million stroke patients who were hospitalized or visited the outpatient clinic that day, approximately 75% had cerebral infarction, 15-20% had cerebral hemorrhage, and 5-10% had subarachnoid hemorrhage. This shows that three-quarters of stroke patients in Japan have cerebral infarction.

What is the cause?

The biggest causes of stroke are said to be high blood pressure and aging. However, there are many other known causes, which are called risk factors. Of course, risk factors differ slightly depending on whether it is cerebral infarction, cerebral hemorrhage, or subarachnoid hemorrhage.

Risk factors for cerebral hemorrhage include high blood pressure, aging, bleeding diathesis (difficulty in blood clotting), arteriosclerosis, etc. The strongest risk factors for subarachnoid hemorrhage are the presence of an aneurysm and high blood pressure.

The most common causes of cerebral infarction are various. In addition to high blood pressure and aging, other causes include diabetes, heart disease, dyslipidemia, obesity, smoking, excessive drinking, stress, dehydration, inflammation, etc. Blood coagulation disorders ( Final examination ) In addition to blood clotting (proneness in blood) and heredity, rare causes include antiphospholipid syndrome, hyperinsulinemia, and hyperhomocysteinemia.

Testing and prevention

Many risk factors can be identified through simple tests. If these factors are found during a health check or medical examination, early lifestyle changes and treatment can help prevent stroke. Although aging and heredity cannot be cured, properly treating other risk factors that exist at the same time can be quite effective in preventing stroke.

MRI scans performed during brain checkups and other similar tests may reveal cerebral infarction (hidden cerebral infarction, etc.) even if the patient is asymptomatic. Silent cerebral infarction ( The high school entrance exam ) Our research shows that these people are more likely to suffer a true stroke in the future.

In some cases, an aneurysm may be discovered before it ruptures. In this case, do not just worry, but consult a specialist doctor (neurologist, brain surgeon, stroke specialist, etc.) as soon as possible. There are various preventive measures.

What to do if you notice an illness

If you feel that you may be having a stroke, even if the symptoms are mild, you should go to a hospital with a specialist as soon as possible. To that end, if you have elderly family members with many risk factors for stroke, it is a good idea to think about which nearby hospital you should take them to in the event of a stroke.

Stroke is a terrible disease, but death can be avoided or aftereffects can be minimized by getting the patient to a well-equipped hospital with specialist doctors as soon as possible.

Yukito Shinohara

Figure 1. Various types of stroke
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Figure 1. Various types of stroke

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

Japanese:

脳卒中とは

　脳卒中という言葉は一般的な用語であり、医学用語ではありません。正式には脳血管障害といいます。脳卒中の卒は卒倒(そっとう)（突然倒れる）の卒で“突然に”の意味、中は中毒（毒にあたる）の中で“あたる”という意味ですから、脳卒中とは脳の病気で突然に何かにあたったようになる（倒れる）ことを意味します。

　これは中国から渡ってきた言葉ですが、西暦760年の日本の書物にすでに見られますから、この病気は日本でも長い歴史をもっていることがわかります。近代医学が発展する前から、人々は卒中という病気があることをある程度理解していたことの証拠でもあります。

脳血管障害の分類

　脳梗塞(のうこうそく)、脳出血(のうしゅっけつ)、くも膜下出血(まくかしゅっけつ)の3つが代表的な脳血管障害です。

　図1に示すように、脳の血管が動脈硬化や、ほかの部位から流れてきたもの（栓子(せんし)といいます）によってふさがってしまうと血流が途絶えてしまいます。その結果、その先の脳組織に血液や血液によって運ばれてくる酸素、ブドウ糖などの栄養物が来なくなり、脳組織が死んでしまうのが脳梗塞です。

　一方、脳の深部の細い血管に高血圧や加齢によって小さなこぶがたくさんでき、これが急に血圧が上昇した時などに破裂して脳のなかに血腫(けっしゅ)ができるのが脳出血、脳の表面の太い血管に動脈瘤(どうみゃくりゅう)ができてそれが破裂し、脳を包む3枚の膜（外から硬膜(こうまく)、くも膜、軟膜(なんまく)）のうち、くも膜と軟膜の間（すなわちくも膜の下）に出血が起こるのがくも膜下出血です。

　そのおのおのについてはあとで詳しく説明します。

　脳卒中は日本の国民病のひとつではありますが、その死亡数は年々減る傾向を示しています。しかしそれは主に脳出血による死亡が減っているからで、脳梗塞やくも膜下出血による死亡はあまり減っていません。

　むしろ死亡率が下がっているわりには発症率が下がっていないので、実際に病院にかかっている患者さんの数は増えています。

　日本におけるある日の調査では、その日に入院中、あるいは外来を訪れた148万人の脳卒中の患者さんのなかで、脳梗塞が約75％、脳出血が15～20％、くも膜下出血が5～10％という結果が出ています。日本で脳卒中で悩む患者さんの4分の3が脳梗塞であることがわかります。

原因は何か

　脳卒中を起こす最大の原因は、高血圧と加齢だといわれています。しかしそのほかにもたくさんの原因が知られており、それらは危険因子と呼ばれています。もちろん、脳梗塞、脳出血、くも膜下出血かによって危険因子は多少違います。

　脳出血は高血圧と加齢に加えて、出血性素因（血が固まりにくいこと）や動脈硬化などが危険因子になります。くも膜下出血は動脈瘤の存在と高血圧が最も強い危険因子です。

　いちばん数の多い脳梗塞の原因はさまざまです。高血圧、加齢のほかに糖尿病、心臓病、脂質異常症、肥満、喫煙、多量飲酒、ストレス、脱水、炎症、血液凝固系異常(けつえきぎょうこけいいじょう)（血が固まりやすいこと）や遺伝のほかに、まれに抗(こう)リン脂質抗体(ししつこうたい)症候群、高インスリン血症や高ホモシスティン血症などが原因になります。