Dizziness, Vertigo

Japanese: めまい（英語表記）Dizziness, Vertigo

How dizziness occurs

In order to maintain balance, movement, and posture in space, we need accurate sensory information about our body's movements and position.

Among these, head tilt and rotation are detected by the inner ear, located deep inside the ear. Semicircular canals ( Three-wheeled vehicle ) or Otolith organs ( History ) Ear disorders cause dizziness because the inner ear sends false signals that the head is moving or rotating, when in fact the head is still.

Visual information from the eyes is also important for balance. There are houses at amusement parks that are intentionally tilted, known as mystery zones, and in these you can experience an abnormal sensation of being pulled down in one direction, a feeling of dizziness.

This phenomenon occurs when the apparent vertical we perceive visually is different from the vertical of gravity sensed by the inner ear. Similarly, information from joints and muscles such as the neck also plays an important role.

When you are healthy, there is no contradiction between these senses, and although you may be able to perceive your own movements and changes in the outside world to a certain extent, you do not feel dizzy. However, as in the example given above, when the balance sensory organs such as the inner ear are not functioning properly, information that differs from your actual posture and movement is transmitted.

When this happens, the signals cause muscle reflexes that are similar to those caused when the head or body is tilted, even though the head or body is not actually tilted, and these abnormal signals are also transmitted directly to the brain. This erroneous information is different from that which occurs with real movements, and does not match well with other visual or proprioceptive information.

Occurs in a variety of diseases

We feel dizziness when multiple sensory information does not match. Therefore, not only diseases of the inner ear, but also abnormalities in vision, neck, and back can cause dizziness. Also, diseases of the brain, which integrates these information inputs, especially the brain stem and cerebellum, which reflexively regulate posture and movement, such as cerebral infarction ( Noise ) or cerebral hemorrhage, Brain tumors ( Newcomer ) But I feel dizzy.

Dizziness can also be caused by various systemic illnesses. Orthostatic hypotension ( Cutting edge police ) If your blood pressure is low, and you suddenly stand up or work for a long time while standing, not enough blood flows to your brain, causing you to feel dizzy or faint.

Conversely, sudden high blood pressure can also cause a floating sensation. Dizziness can also occur when blood flow to the brain is temporarily reduced due to arrhythmia.

In addition, anxiety and worry can sometimes cause dizziness, and in many cases, the anxiety of "recurring" can make the dizziness worse, creating a vicious cycle.

In this way, dizziness is related to abnormalities in various systems, including the sensory organs, locomotor system, brain, and circulatory system. The reason why many types of tests are performed for dizziness is because it is necessary to check for a wide range of abnormalities.

When doctors listen to patients, it is important to

1) Duration of dizziness

② Posture, head position, etc. when dizziness occurs

3) Other symptoms associated with dizziness, such as ringing in the ears, hearing loss, ear congestion, numbness in the hands and feet, or headaches

4) Did you lose consciousness when the dizziness occurred?

And more.

When visiting a medical institution for dizziness, it is a good idea to organize the above points. However, if dizziness is accompanied by a severe headache, loss of consciousness, or numbness or paralysis on one side of the body, it is highly likely to be a cerebrovascular disorder, so please visit an emergency hospital as soon as possible.

Treatment and lifestyle precautions

Treatment for dizziness depends on the illness that caused it, but it is generally divided into acute treatment to suppress dizziness attacks, nausea, vomiting, etc., and intermittent treatment to cure the cause of the dizziness. For specific treatment methods, please refer to the relevant section in this book.

Common points of caution in daily life that are recommended for dizziness patients are:

① Get enough sleep and rest

2) Avoid stress and change your mood through moderate exercise, hobbies, etc.

3. No smoking

And more.

In particular, many patients with Meniere's disease are meticulous and conscientious, and have a strong desire to complete their work perfectly and to be praised by others. Delegating work to others and accepting some imperfections, and shifting to a slightly slower lifestyle, are also important points in overcoming dizziness.

Yasushi Naito

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

Japanese:

めまいが起こる仕組み

　私たちが空間のなかでうまくバランスをとって、運動をしたり姿勢を保ったりするためには、自分の体の動きや位置についての正確な感覚情報が必要です。

　この情報のうち、頭の傾きや回転などは耳の奥深くにある内耳の三半規管(さんはんきかん)や耳石器(じせきき)という部分で感知されます。耳の病気でめまいが起こるのは、実際にはじっとしているのに、頭が動いたり回転したりしているという誤った信号が内耳から発せられるためです。

　目からの視覚情報も、バランスには大切です。遊園地にミステリーゾーンなどといってわざと傾けてつくった家があることがありますが、そのなかでは自分が一方向に引き倒されるような異常な感覚、めまい感を体験することができます。

　これは視覚で認識する見かけの垂直と、内耳が感じる重力の垂直とが食い違うことによって起こる現象です。同様に、首などの関節や筋肉からの情報も大切なはたらきをしています。

　健康な状態では、これらの感覚の間に矛盾はなく、自分の運動や外界の変化をそれなりに知覚することはあっても、これをめまいと感じることはありませんが、前にあげた例のように、内耳などバランスの感覚器の調子が悪くなると、現実の姿勢や動きとは異なる情報が発信されます。

　すると、その信号によって、実際には頭や体は傾いていないのに、それらが傾いた時と同じような筋肉の反射が起こり、また、この異常な信号は直接脳にも伝えられます。これらの誤った情報は、現実の運動で生じるものとは異なり、他の視覚や固有知覚とうまく一致しません。

いろいろな病気で起こる

　私たちは、このような複数の感覚情報の不一致を「めまい」と感じるようです。したがって、内耳の病気だけでなく、視覚、首や腰の異常もめまいの原因となります。また、それらの情報入力を統合する脳、とくに姿勢や運動を反射的に調節している脳幹や小脳の病気、たとえば脳梗塞(のうこうそく)や脳出血、脳腫瘍(のうしゅよう)でもめまいを感じます。

　めまいは、いろいろな全身の病気でも起こります。若い人、とくに若い女性に多いのが起立性低血圧症(きりつせいていけつあつしょう)によるめまいです。日ごろから血圧が低めで、さらに急に立ち上がったり、長い時間立ち仕事を続けたりすると脳に十分な血液が流れなくなって、ふらふらしたり、気が遠くなったりします。

　逆に、急激な高血圧でもふわふわした浮動感を感じます。そのほか、不整脈で一時的に脳への血流が低下した場合にもめまいを生じることがあります。

　また、不安や心配事などがめまいの原因となることがあり、さらに「まためまいが起こるのではないか」という不安がめまいを増悪させるという悪循環になることも多くみられます。

　このように、めまいには感覚器、運動器、脳、循環器などいろいろなシステムの異常が関係します。めまいで多くの種類の検査が行われるのは、広い範囲の異常をチェックする必要があるからです。

　医師が患者さんの話を聞く時にポイントになるのは、

①めまいの持続時間

②めまいが起こった時の姿勢、頭の位置などの状況

③耳鳴りや難聴、耳が詰まる感じ、手足のしびれ、頭痛など、めまいに伴う他の症状

④めまいが起こった時に意識を失ったかどうか

などです。

　めまいで医療機関を受診する時は、このような点を整理して行かれるとよいでしょう。ただし、めまいに伴って激しい頭痛や意識障害、半身のしびれや麻痺などがある場合は脳血管障害の可能性が高いので、できるだけ早く救急病院などを受診してください。