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What is Bell’s palsy?

After you have been diagnosed with Bell’s palsy, your first question will definitely be, “What is Bell’s palsy?”. Let us clear your confusion and elaborate on the ins and outs of Bell’s palsy.

Estimated reading time: 11 minutes


What is Bell’s palsy

In general, Bell’s palsy is a particular diagnosis for a peripheral facial paralysis. Essentially, the correct name of this functional disorder is a peripheral facial paralysis. When the cause of this paralysis cannot be established, it is considered an idiopathic facial paralysis, which then gets the name Bell’s palsy.

In short, Bell’s palsy is a diagnosis given to facial paralysis when its cause is unknown.

In this article, we are discussing a classical Bell’s palsy. The topics of Ramsay Hunt Syndrome, congenital and post-traumatic facial palsy we will discuss in other posts.

Symptoms of Bell’s palsy

Below are the symptoms that are characteristic for acute Bell’s palsy specifically.

  1. Sudden paralysis of facial muscles
    Sudden or quickly developing, within several hours, or at most within one or two days, paralysis of facial muscles. The affected half of the face stops functioning, the eye gets wide open, facial asymmetry at rest is very visible, mouth corner is drooping. You may experience excessive tearing or, on the contrary, your eye may become dry. Affected half of the face cannot be moved.
  2. Possibility of pain
    In most cases, you will not experience any pain, but it is possible that the sudden facial paralysis may be accompanied by painful sensations. Most often, the pain will happen in or behind the ear. Sometimes it can also affect half of the head, or even radiate towards the neck and shoulder area.
    Unfortunately, if you experience pain during the beginning stages of Bell’s palsy, in most scenarios, it means that the damage is quite severe, and your recovery can take a longer time.

Causes of Bell’s palsy

Although in most cases of Bell’s palsy its exact cause cannot be established, let’s discuss three options that can lead to this facial paralysis.

Facial nerve channel
Facial nerve in the pyramid of temporal bone
  1. Local over cooling
    One of the common causes of Bell’s palsy is local over cooling. It happens when a side of your face and neck area become so cold, that it disrupts blood supply in the area. It can happen due to draft winds, air conditioner, cold winds and weather, etc.
    We had one patient who was watching her son skiing. She had a very light jacket and had no hat and no scarf. She had to stay outside in the winter weather for a couple of hours. The next morning, she woke up with a facial paralysis.
  2. Disruption of blood supply
    Either due to local over cooling, or other causes, the blood vessels that supply the facial nerve with oxygen and other nutrients, may become constricted or spasmed. Without oxygen, our nerve cells cannot survive for long.
    If the disruption in blood supply is long (a day or more), it can lead to deeper damage to the facial nerve and a long recovery period.
  3. Bacterial infection of the inner ear
    Bacterial infections of the inner ear, such as Otitis Media, can cause a severe inflammation that spreads and involves the facial nerve. Our facial nerve runs very close to the ear, in the pyramid of the temporal bone. It passes through a very narrow “S”-shaped bone channel.
    Within this channel, our facial nerve is very vulnerable to inflammation and swelling. When the nerve becomes constricted due to the swelling resulting from the infection, it will be damaged and will cease its normal function, resulting in facial paralysis.

Causes of facial palsy

Besides the three causes explained above, there are other possible causes that may lead to facial paralysis. In some cases, doctors may give the diagnosis “Bell’s palsy” even if the paralysis was caused by the factors described below.

  1. Lyme disease
  2. Herpes virus – leading to facial palsy with diagnosis Ramsay Hunt Syndrome
  3. Surgical interventions – in the Cerebellopontine angle or during cosmetic surgeries
  4. Tumours that are located in the Cerebellopontine angle
  5. Traumas – head injuries and temporal bone fractures

Technically, facial paralysis caused by these factors is not “Bell’s palsy”, as the causing factor can be established. In the case of the Herpes virus, the diagnosis of facial palsy is called “Ramsay Hunt Syndrome”.

Risk factors for Bell’s palsy

Now let’s take a look at some of the risk factors that may lead to Bell’s palsy. Usually, it is the combination of risk factors, together with causing factors, that can lead to Bell’s palsy.

Stress can lead to Bell’s palsy.

Stress has been confirmed to be a risk factor for developing Bell’s palsy. It reduces the capacity of our immune system and can lead to various problems in our bodies, including Bell’s palsy. If you experience chronic stress, you may have an increased risk of Bell’s palsy due to over cooling, blood vessel spasms or infections and inflammations in the area where the facial nerve is located.

Last weeks of pregnancy.

During the last weeks of pregnancy or immediately after giving birth, women are at a higher risk of developing Bell’s palsy. It does not mean that the risk is high, it is simply higher than for a healthy human being who is not pregnant.

Diabetes and high blood pressure.

Although diabetes and high blood pressure are not a very common cause of Bell’s palsy, they still contribute as a risk factor to its development.


How Bell’s palsy happens

The first important thing to know is that Bell’s palsy is not a disease. It is a functional disorder. It is more of a trauma to the facial nerve, but not a disease of the facial nerve.

Before we dive into the explanation of Bell’s palsy, let’s take a look at the facial nerve.

Essentially, our facial nerve is like a cable that consists of thousands of thin wires, called axons. Motor neurons connect our brain to the facial muscles and innervate them (provide electrical signals). An axon is a wire of the moto cable that transports the electrical signals from the motor neuron’s cell body all the way to the neuromuscular junction connecting it with the muscle fibres.

The facial nerve
Structure of the facial nerve
Structure of a neuron
Structure of a motor neuron

Just like a normal wire, to be able to conduct electricity the axon needs insulation. The insulation for neurons in our body is provided by myelin sheath. It consists of living cells that contain a protein with electrical insulation properties.

Stage 1: Sheath loss

Due to the compression of the facial nerve or as a result of the reduced blood supply, the myelin sheath will suffer first.

Since the myelin sheath provides electric insulation to the facial nerve, once it is damaged, the insulation is broken. Without the insulation, the electrical signals that are sent from the brain cannot reach the facial muscles, even if the axons remain undamaged. This is called a conduction block.

Stages of facial nerve damage during Bell's palsy
Stages of facial nerve damage during Bell’s palsy

When conduction block happens, you experience paralysis of one side of the face. If the factor that caused this remains unknown, this is then called “Bell’s palsy”. That is also why it happens so suddenly. Once the electrical conductivity is lost, no signals are able to reach your facial muscles.

Stage 2: Disconnection

During the sheath loss stage, only the myelin sheath is damaged. The axon remains intact.

However, if the damaging factor persists for a longer time, the axons of the facial nerve will suffer next.

This leads to a physical disconnection between the brain and the facial muscles. The nerve fibres from the site of damage, that usually takes place in the pyramid of the temporal bone behind the ear, all the way to the facial muscle, will degenerate (die). Luckily, the cell body of the neuron, will remain alive, because the nucleus of the facial nerve is located in the brain. The nucleus of the facial nerve is not affected during Bell’s palsy.

Once the distal part of the motor nerve fibres degenerate, the immune system will clear out the way and get rid of the degenerated cells.

Since the actual nerve cell remain alive, as soon as the damage happens, it will begin to regenerate.

Recovery after Bell’s palsy

The process of damage and recovery of the facial nerve during Bell’s palsy can be compared to regrowth of grass after it has been cut. If you mow a lawn, you will cut off a part of the grass blades. This does not kill the grass itself. The grass root remains alive in the soil. After some time, the grass blades will grow back. It cannot happen as quick as cutting it. It will be growing back at the rate that the nature allows.

The same happens with the facial nerve. After the damage, it will begin to regenerate. It will take some time. The regeneration of the facial nerve under the most optimal circumstances happens at the rate of 1 mm per day, maximum.

The time, while the facial nerve fibres and the myelin sheath are recovering, is known as the acute stage of Bell’s palsy. It is the stage when you experience a full paralysis of one side of your face.

There are generally two scenarios that your recovery can follow. It can be quick, or it can take a longer time.

Short recovery

Superficial damage to the facial nerve
Superficial damage to the facial nerve

A quick recovery after Bell’s palsy will happen if the damage to the facial nerve was superficial. This means that the damaging factor did not remain for long and only the myelin sheath was damaged. Only the sheath loss happened, and the disconnection did not take place – the axon of the motor neuron was not injured.

The myelin sheath takes a few weeks to regenerate. Once the myelin sheath is recovered, the axon recovers its insulation and can provide signals from the brain to the facial muscles again. Since the nerve fibres were not damaged, the recovery in this case will be quick and complete. You are also not likely to experience any complications and residuals.

This Bell’s palsy recovery scenario happens in the majority of cases when it is caused by over cooling or a small disruption of blood supply.

We have a more detailed post describing the timeline and process of a quick Bell’s palsy recovery.

Long recovery

Extensive damage to the facial nerve
Extensive damage to the facial nerve

If the damaging factor stayed longer, then not only the myelin sheath, but also the axon suffered damage. Both the sheath loss and disconnection took place. This happens in approximately 30% or less of all facial palsy cases. Usually, a deeper damage occurs if your Bell’s palsy is caused by a bacterial or viral infection, as well as if the disruption in blood supply was long.

In this case, the recovery takes a much longer time. It can vary from 3-4 weeks (if the damage to the axon was minimal) to 3-4 months. Sometimes, it can take even longer. Our facial nerve recovers very slowly. It needs time to regenerate the damaged axons.

If the recovery is long, the probability of developing complications and residuals is high.

And please, remember, that Bell’s palsy is not permanent. Despite what your doctor or other medical sources may tell you, it does not last forever. Once your facial movements return, you do not have a paralysis any more. Therefore, your Bell’s palsy ends there. You may develop complications and residuals, as a result of a long recovery process. But this is not Bell’s palsy any longer. These residuals and complications will not go away on their own, and can remain for a long time. That is why we developed Neuro-Proprioceptive Method of Rehabilitation – to help reduce manifestations of complications after incomplete Bell’s palsy recovery without surgeries or any other invasive methods.

Signs of recovery

Once the facial nerve and/or its myelin sheath recovers sufficiently, you will start noticing first signs of recovery. Besides the first movements, you may also start feeling some twitching, vibration, itching of your facial muscles. You may notice that your facial symmetry is returning even before that.

To see your recovery, we always recommend measuring and keeping track of your progress every week. This will help you stay positive because you will be able to see that recovery is happening. Especially if it takes a longer time.

Speak with us

If you suffer from Bell’s palsy, and you are confused, scared and frustrated, please do not panic. It will get better. We know that, because we went through this journey with hundreds of our patients. From despair and hatred towards their faces, through daily work, we guided them to love their face again. They managed to improve their condition and bring back their smile.

We are here to guide you on your own journey. Speak with us, we will answer your questions and help you understand better what you can expect from the future.

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Alex Pashov

Co-founder of Crystal Touch clinic and Bell's palsy expert.

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