Facial paresis, also known as facial paralysis, occurs when the muscles on one or both sides of your face stop working properly due to damage to the facial nerve. This condition can affect your ability to smile, close your eyes, speak clearly, or even eat and drink normally, making everyday interactions challenging and often impacting self-confidence.

What Is Facial Paresis?

Facial paresis happens when your facial nerve (also called cranial nerve number seven) becomes damaged or stops functioning correctly. This nerve is responsible for controlling the muscles that allow you to make facial expressions, blink your eyes, and move your mouth. When it doesn’t work properly, you lose the ability to move parts of your face normally.^[1]

The condition can affect just one side of your face, which doctors call unilateral paralysis, or both sides, known as bilateral paralysis. The weakness can range from mild to complete paralysis. In some cases, facial paresis is temporary and improves over time, while in other situations it may become permanent.^[1]

The facial nerve is particularly important because it not only controls movement but also carries signals for taste from the front part of your tongue and helps with tear and saliva production. When this nerve is damaged, multiple functions can be affected beyond just facial movement.^[4]

Understanding the Difference Between Central and Peripheral Facial Paresis

Doctors distinguish between two main types of facial paresis based on where the problem occurs. Understanding this difference is crucial because the causes and treatments vary significantly between the two types.^[3]

Central facial paresis occurs when the damage is in the brain itself, in the area that sends signals to the facial nerve. This type often happens alongside other symptoms like weakness in the arms or legs. With central paresis, the muscles of the upper part of the face (like those that control the forehead and eyelid) usually still work to some degree, so people can still frown and close their eyes somewhat.^[4]

Peripheral facial paresis happens when the facial nerve itself is damaged somewhere along its path from the brain to the face muscles. This is the most common type. With peripheral paresis, all the facial muscles on the affected side are weak, including those controlling the forehead and eyelid. This means people cannot wrinkle their forehead or fully close their eye on the affected side.^[4]

Epidemiology

The most common form of facial paresis is Bell’s palsy, which accounts for roughly seventy percent of all facial nerve paralysis cases. Bell’s palsy occurs when facial weakness develops without any known underlying cause, making it a diagnosis of exclusion after other potential causes have been ruled out.^[3]

Bell’s palsy can affect anyone, occurring at any age. The condition has an incidence rate of ten to forty cases per one hundred thousand people in the general population. This means it is relatively common, and most healthcare providers will encounter many patients with this condition throughout their careers.^[3]

The condition affects men and women similarly, though some risk factors may make certain groups more vulnerable. People who are pregnant, have obesity, chronic high blood pressure, diabetes, or severe complications during pregnancy called preeclampsia appear to have higher risk. Upper respiratory infections also seem to increase the likelihood of developing facial paresis.^[2]

While Bell’s palsy can resolve on its own, not everyone recovers completely. Studies show that about seventy percent of people with complete facial paralysis and ninety-four percent of those with partial paralysis recover within six months. However, this also means that thirty percent of patients with complete paralysis do not fully recover, and up to thirteen percent may have incomplete recovery that lasts beyond one year.^[3][17]

Causes

Facial paresis develops when either the facial nerve itself or the part of the brain controlling facial movement becomes damaged. Some people are born with facial nerve problems, but most people develop the condition later in life due to various causes.^[1]

The most common cause is Bell’s palsy, where the facial nerve becomes swollen and inflamed without a clear reason. Experts believe this might be triggered by viral infections, particularly herpes viruses. The nerve passes through a narrow channel in the bone, and when it swells, it becomes compressed in this tight space. This compression reduces blood flow and oxygen to the nerve, causing it to malfunction.^[3]

Physical trauma is another significant cause, accounting for ten to twenty-three percent of facial paresis cases. Fractures involving the temporal bone (the part of the skull near the ear) can damage the facial nerve. These fractures require tremendous force and often come with other signs like bleeding behind the eardrum or bruising behind the ear. Facial wounds that cut through branches of the facial nerve can also cause paralysis.^[3]

Infections represent another important group of causes. Ramsay Hunt syndrome occurs when the herpes zoster virus (the same virus that causes shingles and chickenpox) reactivates in the facial nerve. This virus lies dormant in the nerve after a previous infection and can suddenly become active again. Lyme disease, caused by bacteria transmitted through tick bites, can also affect the facial nerve.^[1][3]

Middle ear infections can spread to involve the facial nerve since it passes through the middle ear area. Tumors growing on or near the facial nerve can gradually compress it, leading to slowly worsening facial weakness. These include acoustic neuromas (tumors on the hearing nerve) and tumors in the head, neck, or brain that press on facial nerve structures.^[1]

Medical procedures can sometimes inadvertently damage the facial nerve. Surgery involving the ear, parotid gland (a salivary gland in front of the ear), or removal of acoustic tumors carries risk of facial nerve injury. This is called iatrogenic injury, meaning it results from medical treatment.^[3]

Autoimmune diseases, where the body’s immune system mistakenly attacks its own tissues, can affect the facial nerve. Conditions like multiple sclerosis, sarcoidosis, and Guillain-Barré syndrome fall into this category. Stroke, which damages brain tissue by cutting off blood supply, can cause facial weakness along with other neurological symptoms.^[1]

Risk Factors

Several factors can increase your likelihood of developing facial paresis. Understanding these risk factors helps identify who might be more vulnerable and may benefit from closer monitoring or preventive measures when possible.^[2]

Pregnancy increases the risk of developing Bell’s palsy, particularly during the third trimester and shortly after delivery. The reasons for this increased risk are not completely understood but may relate to fluid retention, hormonal changes, and altered immune function during pregnancy. Women with severe preeclampsia face even higher risk.^[2]

People with diabetes mellitus have a greater chance of developing facial nerve problems. High blood sugar levels over time can damage nerves throughout the body, including the facial nerve. Similarly, chronic high blood pressure affects blood vessels and may compromise blood supply to nerves.^[2]

Obesity appears to be associated with higher rates of facial paresis. The mechanisms behind this connection are still being studied but may involve inflammation, metabolic factors, and effects on blood vessel health that come with excess weight.^[2]

Recent upper respiratory infections often precede the development of Bell’s palsy. Many patients report having cold-like symptoms or flu in the days or weeks before their facial weakness began. This pattern supports the theory that viral infections may trigger the nerve inflammation that leads to paralysis.^[2]

People living in areas where Lyme disease is common face risk of facial paresis from tick-borne bacterial infection. Outdoor activities in wooded or grassy areas during tick season increase exposure to this risk. Anyone who develops facial weakness during tick season or after known tick bites should be evaluated for Lyme disease.^[1]

Previous episodes of Bell’s palsy slightly increase the chance of experiencing it again. While most people have only one episode in their lifetime, up to ten percent may have recurrent facial paralysis.^[3]

Symptoms

The symptoms of facial paresis typically develop suddenly, often appearing over the course of just a few hours to a couple of days. The speed of onset and the specific symptoms can help doctors understand the cause and severity of the condition.^[2]

The hallmark symptom is weakness on one side of the face, ranging from mild weakness to complete paralysis. When you try to smile, only one side of your mouth moves up, creating a lopsided appearance. The affected side of your face appears to droop, and your facial expressions become uneven and difficult to control.^[2]

Eye problems are particularly concerning with facial paresis. You may find it difficult or impossible to fully close the eye on the affected side. Your eyelid may not close completely during sleep, leaving the eye partially open. Blinking becomes impaired, which means the eye doesn’t get properly moistened and protected. This can lead to excessive tearing as the eye tries to compensate, or paradoxically, to dryness if tears cannot drain properly. The eye may feel gritty, irritated, or painful.^[2]

Forehead movement becomes affected in peripheral facial paresis. You cannot wrinkle your forehead or raise your eyebrow on the paralyzed side. This is an important distinguishing feature that helps doctors determine whether the problem is with the nerve itself or with the brain.^[4]

Eating and drinking become challenging. Drooling occurs because you cannot keep your lips properly closed on the affected side. Food and liquids may leak from the corner of your mouth. You might notice food collecting between your cheek and gums on the paralyzed side because you cannot feel it there or move it around with your tongue and cheek muscles. Chewing requires extra effort and concentration.^[2][17]

Speaking clearly becomes more difficult because precise lip and mouth movements are essential for forming many speech sounds. Your words may sound slurred or imprecise, and others might have trouble understanding you. This can be frustrating and may cause you to avoid social situations.^[6]

Pain can accompany facial paresis. Some people experience pain around the jaw or in or behind the ear on the affected side. This pain might appear before the facial weakness becomes obvious or might develop as the condition progresses.^[2]

Changes in taste sensation affect the front two-thirds of your tongue on the affected side. Foods may taste different or bland because the facial nerve carries taste information from this part of the tongue. Loss of taste can reduce appetite and make eating less enjoyable.^[4]

Increased sensitivity to sound in the affected ear occurs when the tiny stapedius muscle in the middle ear becomes paralyzed. This muscle normally dampens loud sounds, and when it doesn’t work, everyday noises can seem uncomfortably loud or jarring.^[2]

The psychological and social impact of facial paresis should not be underestimated. Your face is central to how you express emotions and communicate with others. When you cannot smile, show surprise, or convey concern through facial expressions, social interactions become strained. Many people with facial paresis experience decreased self-esteem, anxiety about their appearance, and reluctance to participate in social activities. This emotional burden can significantly affect quality of life.^[3][5]

Prevention

Preventing facial paresis can be challenging because the most common form, Bell’s palsy, occurs without a clearly identifiable preventable cause. However, addressing risk factors and taking precautions against known causes can reduce your chances of developing this condition.^[2]

Managing chronic health conditions effectively offers some protective benefit. Keeping diabetes well-controlled through proper medication, diet, and lifestyle helps protect nerves throughout the body, including the facial nerve. Regular monitoring of blood sugar levels and working closely with your healthcare provider to maintain target ranges is important.^[2]

Controlling high blood pressure through medication, reducing salt intake, maintaining healthy weight, exercising regularly, and managing stress protects blood vessels and ensures adequate blood supply to nerves. Regular blood pressure checks and medication compliance are essential components of this prevention strategy.^[2]

Maintaining a healthy weight through balanced nutrition and regular physical activity may reduce risk since obesity is associated with higher rates of facial paresis. Even modest weight loss can provide health benefits and potentially lower risk.^[2]

Preventing Lyme disease in areas where ticks are common involves several protective measures. When spending time outdoors in wooded or grassy areas, wear long sleeves and pants, use insect repellent containing DEET, and check yourself thoroughly for ticks after outdoor activities. Removing ticks promptly (within 24-36 hours) significantly reduces the chance of disease transmission. If you find an attached tick, remove it carefully with fine-tipped tweezers and monitor for signs of infection.^[1]

Protecting your head from injury helps prevent trauma-related facial nerve damage. Wearing helmets during activities like cycling, motorcycling, skiing, or contact sports reduces the risk of skull fractures that could damage the facial nerve. Using seat belts in vehicles provides crucial protection during accidents.^[3]

Seeking prompt treatment for ear infections prevents them from spreading to affect the facial nerve. If you experience ear pain, drainage, or hearing changes, see your healthcare provider rather than waiting to see if it resolves on its own.^[1]

If you have had chickenpox, you carry the herpes zoster virus that can cause Ramsay Hunt syndrome. While you cannot eliminate this virus from your body, vaccination against shingles (herpes zoster) for adults over fifty years old can reduce the risk of viral reactivation and the complications that come with it, including facial nerve involvement.^[3]

Pathophysiology

Understanding what happens inside the body when facial paresis develops helps explain why symptoms occur and guides treatment approaches. The pathophysiology involves complex changes in nerve structure and function.^[3]

The facial nerve is the seventh cranial nerve and has a complex path from the brain to the face muscles. It originates in the brainstem (specifically in an area called the pons) and travels through a narrow bony channel within the temporal bone before emerging and branching out to supply various facial muscles. This journey through tight bony passages makes the nerve vulnerable to compression when swelling occurs.^[4]

In Bell’s palsy, the exact trigger remains unknown, but inflammation of the facial nerve is the central problem. When the nerve becomes inflamed, it swells within its confined bony canal. Because the bony channel cannot expand to accommodate the swollen nerve, pressure builds up. This increased pressure compresses the nerve and restricts blood flow through the tiny vessels that supply it.^[3]

When blood flow to the nerve decreases, the nerve tissue experiences ischemia, meaning it doesn’t receive enough oxygen and nutrients. Nerve cells are particularly sensitive to oxygen deprivation. Without adequate oxygen, the nerve cannot generate or transmit electrical signals properly, and communication between the brain and facial muscles breaks down. This is why facial muscles become weak or paralyzed even though the muscles themselves are healthy.^[3]

The severity and duration of nerve compression determine the extent of damage. With mild compression and brief inflammation, the nerve may only be temporarily unable to conduct signals but remains structurally intact. In these cases, once swelling decreases and normal blood flow resumes, nerve function returns relatively quickly and completely.^[3]

With more severe or prolonged compression, actual structural damage to the nerve fibers can occur. The protective covering around nerve fibers, called myelin, may break down. This process, called demyelination, significantly impairs the nerve’s ability to transmit signals efficiently. However, myelin can regenerate, and recovery is still possible, though it takes longer.^[3]

In the most severe cases, the nerve fibers themselves (called axons) may die. When this happens, the nerve must regrow from the point of damage all the way to the muscles it supplies. Nerve regrowth occurs slowly, at roughly one millimeter per day. Depending on how far the nerve must regrow, this can take many months. Sometimes, regenerating nerve fibers grow back incorrectly, connecting to the wrong muscle groups. This can result in synkinesis, where unintended facial movements occur, such as the eye closing when trying to smile.^[1]

When facial muscles do not receive nerve signals for an extended period, they can begin to weaken and shrink from disuse, a process called atrophy. If nerve supply is not restored within approximately two years, the muscles may become so damaged that they cannot function even if nerve connection is eventually restored. This is why the timing of interventions matters significantly for chronic facial paralysis.^[12]

In cases caused by viral infections like Ramsay Hunt syndrome, the virus directly attacks nerve cells, causing inflammation and cell death. In trauma-related facial paresis, physical tearing or cutting of nerve fibers causes immediate loss of continuity in the communication pathway. With tumors, gradual compression over time slowly strangles the nerve’s blood supply and physically distorts its structure.^[3]

Central facial paresis involves different pathophysiology. Here, the problem lies not in the facial nerve itself but in the neural pathways from the brain’s motor cortex to the facial nerve nuclei in the brainstem, or in damage to the brainstem nuclei themselves. Conditions like stroke interrupt these pathways by cutting off blood supply to brain tissue, causing cell death in the affected area. Because of how facial movement is organized in the brain, with the upper face receiving some input from both sides of the brain, central lesions typically spare forehead movement.^[4]