Facial paralysis (Bell's palsy)

Japanese: 顔面神経麻痺（ベル麻痺） - がんめんしんけいまひ（ベルまひ）（英語表記）Facial paralysis (Bell palsy)

What is the disease?

Facial paralysis is the motor paralysis of the facial muscles controlled by the facial nerve. It develops acutely or subacutely. Symptomatic ( Introduction ) Facial paralysis with no apparent cause Idiopathic ( Special life ) Facial paralysis (Bell's palsy) can be classified as

The most common cause is herpes virus infection, typically lip ( Public health ) People who have previously had herpes may suddenly develop facial paralysis. tumor ( Main ) In addition to motor nerves, the facial nerve also controls the taste buds in the front two-thirds of the tongue and the stapedius muscle, a small muscle that regulates the volume of the tongue.

What is the cause?

The cause of idiopathic facial nerve palsy is still unknown, but possible causes include Cold exposure ( Relief Bomb ) ,allergy, Localized edema ( Recruitment ) , viral infections, etc.

In any case, the facial nerve exits the brain through a narrow tunnel surrounded by bones called the facial nerve canal, and it is thought that if the facial nerve becomes swollen (edema) for some reason, the facial nerve becomes compressed and paralysis occurs.

How symptoms manifest

Typical symptoms of Bell's palsy include:

① The main symptom is sudden motor paralysis of one side of the face, regardless of gender or age. As a result, the patient is unable to wrinkle the forehead, close the eyes, have drooping corners of the mouth, and cannot speak. Point ( Toga ) Symptoms include difficulty whistling and drooling from the corners of the mouth (Figure 30).

② The ear on the affected side may become sensitive, making sounds seem louder.

3) There may be a loss of taste in the front two-thirds of the tongue on the paralyzed side. A typical complaint is a feeling of metal in the mouth when eating.

4. It is difficult to close the eyes, so the eyes are filled with tears. Jun ( Moisturize ) This means that the cornea becomes more susceptible to drying out at night. Ulcers ( Canker ) There are things you can do.

⑤The prognosis is relatively good, and the condition may heal naturally within a few months.

⑥If healing is incomplete, facial paralysis may remain. Also, if the regenerated facial nerve controls muscles different from the original one, abnormal combined movements such as closing the eyes when closing the mouth or crying when eating hot or cold foods may occur.

Testing and diagnosis

Diagnosis is relatively easy based on the typical facial expression. However, if there is an underlying disease, if it occurs on both sides at the same time, or if it recurs repeatedly, imaging such as MRI is required. In addition, it can also be caused by relatively rare diseases such as sarcoid and Lyme disease, and if these are suspected, other tests such as blood tests will be required.

Before the onset of facial paralysis, you may experience pain or pain in your ears. Blisters ( Water ) If the formation of erythema precedes, paralysis due to herpes virus infection is the first to be considered. In addition, electromyography and evoked potential tests may be performed to accurately evaluate the degree of damage and recovery.

Treatment methods

Generally, treatment can be done on an outpatient basis, but hospitalization is necessary in some cases, such as when testing is required, when the diagnosis is unclear, or when the facial nerve paralysis is severe.

Corticosteroid therapy is thought to be effective, but should be used with caution in the presence of diabetes or infections, as these conditions may worsen. Vitamin _B12 and vitamin E preparations are also used to promote nerve repair.

Even if there is no obvious evidence of herpes virus infection, there have been recent reports that administration of antiviral drugs can improve facial nerve paralysis, so antiviral drugs may be administered at the same time. Artificial tears ( Human Rights Station ) It is necessary to apply eye drops to protect the cornea.

Rehabilitation therapy is also important, and it is effective to gently massage the paralyzed muscles and practice making different faces to activate the facial muscles.

Hiroyuki Nodera, Ryuji Kaji

Figure 30 Typical facial appearance of Bell's palsy
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Figure 30 Typical facial appearance of Bell's palsy

Facial paralysis
Facial paralysis
(Childhood illnesses)

What is the disease?

Paralysis of the facial muscles occurs due to facial nerve damage during childbirth.

What is the cause?

The facial nerve branches off from the brain, passes through a canal in the skull that opens in front of the ear, and comes out to the surface to be distributed to the facial muscles. Facial nerve paralysis occurs when the nerve is edema or torn due to strong pressure on the part that penetrates the skull during childbirth.

How symptoms manifest

In most cases, it only occurs on one side. Symptoms include being unable to close the eye on the paralyzed side, the mouth being convulsed and unable to open wide, and milk dripping from the corner of the mouth on the paralyzed side. This is especially evident when the baby cries.

Treatment and Prognosis

It usually heals naturally within 2 to 3 weeks. During that time, eye drops are used to prevent the cornea of the eye that cannot be closed from drying out. If the nerve is torn, surgery is required to repair the nerve.

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

Japanese:

どんな病気か

　顔面神経麻痺は、顔面神経によって支配されている顔面筋の運動麻痺です。急性あるいは亜急性に発症します。原因疾患が明らかな症候性(しょうこうせい)顔面麻痺と、明らかな原因が不明な特発性(とくはつせい)顔面神経麻痺（ベル麻痺）とに分けられます。

　原因疾患として多いのは、ヘルペスウイルス感染症で、典型的には口唇(こうしん)ヘルペスを以前患った方が突然の顔面神経麻痺で発症します。ほかには腫瘍(しゅよう)や代謝疾患が原因となる場合もあります。顔面神経は、運動神経以外にも舌の前3分の2の味覚を伝達したり、アブミ骨筋という音量を調節する小さな筋を支配しています。

原因は何か

　特発性顔面神経麻痺の原因はいまだ不明ですが、考えられる可能性としては寒冷曝露(かんれいばくろ)、アレルギー、局所浮腫(きょくしょふしゅ)、ウイルス感染などがあります。

　いずれにしても、顔面神経は顔面神経管と呼ばれる骨で取り囲まれた狭いトンネルを通って脳から外に出ますが、何らかの原因で顔面神経がはれる（浮腫）と顔面神経が圧迫され麻痺が現れると考えられています。

症状の現れ方

　ベル麻痺の典型的な症状は以下のとおりです。

①男女差、年齢層に関係なく、突然始まる片側顔面筋の運動麻痺が主な症状です。その結果、額にしわを寄せられない、眼を閉じられない、口角が垂れ下がる、口を尖(とが)らせて口笛がふけなくなる、口角からよだれが垂れる、などの症状が起こります（図30）。

②麻痺側の耳が過敏になり、音が大きく響くように感じることがあります。

③麻痺側の舌の前方3分の2の味覚障害を伴うことがあります。典型的な訴えとしては、ものを食べた時、金属を口に入れたような感じがするというものです。

④眼が閉じにくいため、眼を涙で潤(うるお)すことができず、夜間などに角膜が乾燥しやすくなります。そのため、角膜に潰瘍(かいよう)ができることがあります。

⑤比較的予後は良好で、数カ月で自然治癒することもあります。

⑥治癒が完全でない場合には、顔面麻痺が残ることがあります。また再生した顔面神経が本来の支配先と異なった筋を支配してしまった場合には、口を閉じると眼が一緒に閉じたり、熱いものや冷たいものを食べた時に涙が出たりする異常連合運動が起こることがあります。

検査と診断

　診断は典型的な顔の表情から比較的容易です。しかし、原因となる病気がある場合、両側に同時に発症したり何度も繰り返す場合などは、MRIなどの画像診断が必要です。そのほかにサルコイド、ライム病などのややめずらしい病気でも起こることがあり、それらが疑われる場合には、血液検査などほかの検査が必要になります。

　顔面神経麻痺の発症前に、耳のなかに痛みや水泡(すいほう)の形成が先行する場合は、ヘルペスウイルス感染による麻痺がまず考えられます。また、障害の程度や回復の正確な評価のために、筋電図や誘発電位検査が行われることもあります。