What is facial nerve palsy (facial paralysis)?
Facial nerve palsy is a paralysis (paresis) of the facial nerve. Impulses from the brain travel through it to the muscles of the forehead, cheeks, mouth and neck. It controls all the major muscles of your face, plus the flow of saliva and tears, the glands of the nasal mucosa, and the sense of taste on the front two-thirds of the tongue. If the facial nerve is damaged, the muscles and glands associated with it no longer function correctly.
The damage can occur both in the brain, such as from a stroke or brain tumor. Or the nerve itself is attacked, for example by an infection with bacteria or viruses. In the latter case, facial nerve palsy occurs idiopathically in about two-thirds of cases. That is, no direct cause can be found. Idiopathic facial nerve palsy, also known as Bell’s palsy after the London physician Charles Bell, affects about 7 to 40 per 100,000 people each year. It is the most common cranial nerve disease. Both sexes are affected about equally often. The risk of this increases with age. In addition, the risk of women during pregnancy is increased threefold.
If facial paralysis is properly recognized and treated, it can be cured in the vast majority of cases. Rarely does a clear consequence such as an asymmetrical face remain.
Facial nerve palsy: causes and risk factors
Medicine differentiates two different forms of facial nerve palsy:
Central facial nerve palsy: The damage affects the brain. Possible causes are:
- Stroke (cerebral infarction, cerebral hemorrhage): The blood supply to the brain is suddenly interrupted, resulting in failures of the central nervous system and possibly paralysis of certain parts of the body.
- Brain tumor: A tumor can affect the region of the brain that controls the facial nerve.
Peripheral facial nerve palsy: The facial nerve directly is damaged. In 70 percent of cases, facial paralysis develops idiopathically as a result of the peripherally damaged facial nerve, i.e., without a clearly identifiable trigger. In the remaining approximately 30 percent, facial nerve palsy is the result of an infectious or inflammatory disease, when this affects the facial nerve in addition to certain organs. The facial paralysis symptoms then appear acutely along with other typical symptoms. Causes of peripheral facial nerve palsy due to inflammation may include:
- Infection with the viruses herpes simplex, herpes zoster (shingles) or its special form zoster oticus, which specifically attacks the ear area. It leads to facial paralysis in two-thirds of cases.
- Lyme disease, caused by the tick-borne bacterium Borrelia burgdorferi.
- Middle ear infection: It sometimes spreads to the ramification of the facial nerve, which runs between the tympanic cavity and the mastoid process.
- Meningitis: It can spread to the facial nerve.
- Melkersson-Rosenthal syndrome: An inflammatory disease of unknown cause with multiple symptoms, including sometimes facial paralysis.
- Sarcoidosis: The disease of connective tissue usually affects multiple organs and can cause facial paresis.
- Sjögren’s syndrome: The body’s own immune cells attack the salivary and lacrimal glands. Paralysis of the facial nerve can be one of the consequences.
Nerve injury, such as after a skull fracture or soft tissue injury, can also lead to peripheral facial nerve injury, such as after a skull fracture or soft tissue injury palsy.
Risk factors for facial nerve palsy
- Hypertension and diabetes mellitus are considered risk factors for facial paralysis. If the blood values are inadequately adjusted, the elevated blood sugar not infrequently damages the nerves, sometimes even the facial nerve.
- Extreme stress can also promote facial paralysis. Occasionally, cold drafts are known to be a trigger.
- During pregnancy, the risk of facial nerve palsy is also increased.
- Newborns can develop facial palsy if the facial nerve is compressed in the birth canal or by forceps use during birth.
Symptoms: Mostly unilateral paralyzed facial expression
Facial nerve palsy usually develops within 24 to 48 hours. It often begins with pain behind the ear. The main symptom is paralysis of the muscles on one half of your face. Usually the side is affected where the nerve is damaged. This means you can only smile, speak, whistle, wrinkle your nose, frown or frown, blink with difficulty. Usually one corner of the mouth hangs down, a small region behind the ear shows disturbed sensation.
In addition, the following symptoms may occur:
- Overall asymmetrical face
- You can no longer close one eye completely.
- If you can only close the eyelid incompletely, the eyeball moves upwards (positive bark phenomenon).
- Because your cheek and lip muscles are paralyzed, you have difficulty speaking.
- The skin between the nose and the corner of the mouth and on the forehead is suddenly wrinkle-free.
- They are hypersensitive to sounds.
- Your sense of taste is disturbed.
- They produce less tear fluid and saliva.
If central facial paresis (damage to the nerve cells in the brain) is the trigger for facial paralysis, it primarily affects the mimic muscles in the mouth area. Then you can still move your forehead muscles.
Facial paresis diagnosis
If one of the corners of your mouth droops and you can only close one eye incompletely, we can tell from these symptoms that you have facial nerve palsy. Moreover, if you cannot frown, pucker your lips or puff out your cheeks, this confirms the suspicion.
To determine the extent of facial paralysis, we can perform various tests. Here, different disciplines of the USZ work closely together in a network. Investigations include:
- A taste test shows whether you can distinguish between sweet, sour, salty or bitter on the tongue. If not, your taste buds are also affected.
- The Schirmer test determines whether your eye is producing enough tear fluid. For the test, we place narrow strips of paper in the lower lid of both eyes. By comparing, we can tell if there is a decreased tear flow in one.
- We use a special procedure (impedance measurement) to check whether the stapedius reflex, the mechanism that protects your inner ear from excessive loudness, is still intact.
- We use an otoscope (ear funnel equipped with a light and magnifying glass) to perform an otoscopy. This allows us to see if vesicles on the eardrum or in the ear canal suggest zoster oticus.
- With the help of electromyography (EMG)-a method of measuring electrical currents in the muscle-we can determine whether a muscle or the nerve supplying it is damaged. We may combine this examination with determination of nerve conduction velocity(electroneurography) if nerve damage is suspected. Depending on the results, a decision is made about possible surgical reconstruction of the damaged nerve.
- A blood test can reveal whether an underlying disease may have caused the facial nerve palsy. On the basis of the blood values, we recognize the following causes, for example:
- Lyme disease
- Infection with the herpes simplex virus or varicella zoster.
- Tick-borne encephalitis (TBE)
- Diabetes mellitus
- An X-ray of your skull will show if any fractures or bony changes may have affected nerve function and caused the facial paralysis.
- In individual cases, it may be necessary to exclude a brain tumor as a trigger with the help of a computer tom ography or magnetic resonance imaging.
- Sometimes spinal fluid (CSF) testing for pathogens is also appropriate.
Facial nerve palsy: prevention, early detection, prognosis
Since the cause of idiopathic facial nerve palsy is unknown, you cannot prevent it. If facial paralysis is concomitant with a disease such as Lyme disease, zoster oticus, or diabetes, it is critical that you treat the causative disease early.
Early detection of facial paralysis
Early detection of facial nerve palsy is difficult because it usually occurs relatively suddenly.
Course and prognosis
The course of facial paralysis depends on its cause. In the case of the most common form, idiopathic facial nerve palsy, there is a good chance that the disease will develop favorably. In over 80 percent of cases, symptoms resolve on their own within six weeks to six months. Facial paralysis resulting from an accident also has a good chance of recovery.
However, some affected individuals retain unintentional co-movements of the mimic muscles (so-called synkinesias) even after optimal treatment. Less than ten percent have to deal with permanent facial asymmetries that can affect them visually.
Furthermore, in the course of healing, the so-called crocodile tear phenomenon may develop: In this case, a one-sided flow of tears occurs during eating. This is due to incorrect cross-linking between taste fibers and tear gland during the formation of new nerve fibers. It occurs when facial paralysis heals incorrectly. In addition, in about 7 out of 100 cases of idiopathic facial nerve palsy, paralysis of the same or the other half of the face follows again later.
The exchange with people who are affected by the same disease can be a great support in coping with the disease. Advice on finding a suitable self-help group is available from Selbsthilfe Zürich. Self-Help Zurich and the University Hospital Zurich are cooperation partners in the national project “Health literacy thanks to self-help-friendly hospitals”.
Facial paresis: Treatment depending on the cause
The therapy of facial nerve palsy is two-pronged: On the one hand, we treat the underlying disease, on the other hand, we treat the direct effects of the paralysis symptoms.