In our experience, no. Facial muscles do not waste away (atrophy) after Bell’s palsy, however much time has passed. What many people notice, such as a flatter or thinner cheek, is atonicity: lower muscle tone, because the muscles received weaker signals for a long time. Atonicity can be reversed.
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Why atrophy does not happen after Bell’s palsy
No, Bell’s palsy does not cause atrophy of facial muscles.
From our point of view, the atrophy of facial muscles does not happen after Bell’s palsy. It does not matter how much time has passed since the onset. This is because the facial muscles do not receive their sensory innervation through the facial nerve.
Bell’s palsy only affects the motor neurons of our face.
The facial nerve consists mostly of motor neurons, which are responsible for the movement signals. It also provides signals to salivation and lacrimation glands, which is why you might have excessive tears or lack of them. Also, the sensory (taste) signals to the first 2/3rd of the tongue are provided by the facial nerve. That is why you might have experienced the disruption of the normal taste during the acute stage of your facial palsy. Eventually, this subsides after a few weeks. This is the main reason why the atrophy of the facial muscles does not happen during facial palsy.
How the facial nerve differs from other nerves
The atrophy of facial muscles does not happen during facial palsy because our facial nerve is different from other nerves in our body.
If we damage the skeletal nerve, let’s say the median nerve, which innervates some muscles in our palm and arm, atrophy might take place. The median nerve and all skeletal nerves of our body that provide the movement are mixed. They consist of both sensory and motor fibres. If this nerve is damaged, the brain does not receive any signals from the affected muscles. So the signs from the brain cannot reach the muscles, and also the signals from the muscles cannot reach the brain.
As long as the brain cannot hear anything from the muscles, it may think “OK, this muscle is dead, this soldier is dead, it makes no sense to send him ammunition, supplies and so on and so on”. So it just starts to ignore that muscle in its nutritional and trophic processes, and the muscle sustains atrophy. Atrophy means – malnutrition. So these muscles shrink and become replaced by the fibrous tissue and permanently lose their ability to function, at least partly.
The sensory signals from our facial muscles are conducted by the Trigeminal nerve, which is not affected by facial palsy. That is why you do not lose the sensitivity of your skin. You also do not lose the pain sensation in your face. You may feel some numbness in your facial muscles, especially in the acute phase. That is mostly because you lack movements. The Trigeminal nerve, which senses the movements, contractions, and relaxations of our muscles, lacks signals. That is why it provides the brain with a certain feeling of numbness. What you might experience is atonicity, a lack of tone in your facial muscles, but not atrophy.
What is atonicity?
Atonicity is reduced tone in the facial muscles. While the facial nerve is still recovering, the signals that reach the muscles are weaker than usual. The muscles work less, so they lose some of their tone.
Think of a broken leg. If you do not use your leg for a while, its muscles become smaller and weaker. That is loss of tone, not wasting away, and it comes back when you use the leg again.
“My cheek is not as full as the other side”
A reader asked us: “I was diagnosed with Bell’s palsy 11 months ago. My cheek on my affected side is not as full as the other side and I do not have my full smile back. Has my cheek atrophied?”
No. At 11 months, the facial nerve is usually still recovering. The thinner cheek is atonicity, and the missing smile is often related to synkinesis, muscles pulling against each other.
Can atonicity be reversed?
Yes. Atonicity is reversible and not a reason to despair. The facial nerve can keep recovering for several years, although more and more slowly, until it reaches a stable level.
In our clinic we use micro-stimulation of the nerve. It does not use electric shocks, so it is not the same as electrical stimulation. In a number of our patients, we have seen the nerve start recovering again, even several years after the onset. The Nerve Conduction Study we do before and after rehabilitation shows this as better nerve conduction.
A thinner cheek is one of the long-term effects of Bell’s palsy. If you are unsure what is happening in your face, book a video consultation.
In our clinical experience, no. The facial muscles keep their sensory connection to the brain through the trigeminal nerve, which Bell’s palsy does not affect. What people notice is usually lower muscle tone, not wasting.
The muscles on the affected side received weaker signals for a long time, so they lost some tone. This is called atonicity. It can make the cheek look flatter.
Atrophy means the muscle wastes away and is replaced by fibrous tissue. Atonicity means the muscle is healthy but has less tone because it has been used less. Atonicity can be reversed.
Yes. As the nerve recovers and the muscles are used normally again, tone can return. Rehabilitation can help, even years after the onset.
