Bell's palsy: what is it, causes, symptoms, treatment, prognosis

What is Bell's palsy?

Bell's palsy Is a form of temporary facial paralysis caused by injury or trauma to the facial nerves. The facial nerve, also called the seventh cranial nerve, travels through a narrow bony canal (called the fallopian canal) in the skull under the ear to the muscles on each side of the face. For most of its travel, the nerve is enclosed in this bony sheath.

Each facial nerve directs muscles on one side of the face, including those that control blinking and closing the eyes, as well as facial expressions (smile and frown). Additionally, the facial nerve carries nerve impulses to the lacrimal and salivary glands, the muscles of the small bone in the middle of the ear. The facial nerve also transmits the taste sensations from the tongue.

When Bell's palsy occurs, the function of the facial nerve is impaired, causing the messages that the brain is sending to the facial muscles to be interrupted. This interruption results in facial weakness or paralysis.

Bell's palsy is named after Sir Charles Bell, a 19th century Scottish surgeon who described the facial nerve and its relationship to the condition. Bell's palsy, which has nothing to do with stroke, is the most common cause of facial paralysis. As a rule, it affects only one of the two facial nerves, therefore it appears only on one side of the face, but in rare cases it can affect both sides at the same time.

Signs and symptoms

Early symptoms of Bell's palsy may include:

• slight fever (fever);
• pain behind the ear;
• stiff neck;
• weakness and / or stiffness on one side of the face.

Symptoms can start suddenly and progress quickly over several hours, sometimes after exposure to cold or draft. Part or all of the person may be affected.

In most cases of Bell's palsy, only facial muscle weakness occurs, and facial paralysis is temporary. Most cases resolve in two to three weeks. Approximately 80% of cases are resolved within three months. However, some cases persist. Occasionally, only the upper or lower half of the face is affected.

In severe cases of Bell's palsy, the facial muscles on the affected side are completely paralyzed, resulting in that side of the face becoming smooth, expressionless, and motionless. Often, the opening between the upper and lower eyelids (palpebral fissure) enlarges and remains open during sleep. This can lead to the inability to close the eye on the affected side. People with Bell's palsy may not have a corneal reflex, hence the eye on the affected side does not close when the cornea is touched.

If the compressed area of ​​the facial nerve is close to the branching of other nerves, there may be a decrease in the production of saliva and / or tears. Some people with Bell's palsy experience loss of taste on one side of the mouth, drooling, and increased sensitivity to sound (hyperacusis) on the affected side of the head. In some cases, the victim's response to the injection behind the ear is also reduced.

Recovery from Bell's palsy depends on the extent and severity of the damage to the seventh cranial nerve. If the facial paralysis is only partial, complete recovery can be expected. The affected muscles usually return to their original function within one to two months.

If, as the nerve fibers recover, they grow together with muscles that are different from those that they originally innervated, voluntary movements of the muscles of the face may appear, accompanied by involuntary contractions of other muscles of the face (synkinesis). Sometimes Bell's palsy develops a phenomenon called crocodile tears (tears not triggered by emotion) associated with facial muscle contractions.

Causes and risk factors

The disease occurs as a result of an inflammatory process or compression of the facial nerve; a specific cause has not been identified, but a correlation with viral infectious processes is observed in most cases. In fact, a person infected with the virus can also develop inflammation of the facial nerve; this causes swelling, which in turn causes an increase in pressure in the canal that the nerve crosses (the so-called fallopian canal), with a consequent decrease in blood and oxygen flow to the nerve cells. Sometimes damage only affects the nerve sheath (myelin sheath); in this case, recovery from Bell's palsy occurs fairly quickly.

Viral infections associated with the onset of Bell's palsy:

• herpes simplex virus (responsible for various diseases such as herpes)
• herpes zoster virus (the viral agent that causes shingles and chickenpox)
• Epstein-Barr virus (pathogen infectious mononucleosis)

Other associated viruses are those that cause diseases such as:

• cold;
• viral meningitis;
• flu;
• foot and mouth disease;
• acquired immunodeficiency syndrome;
• rubella;
• viral otitis and etc.

Other pathological conditions include:

• Lyme disease (borreliosis);
• arterial hypertension (high blood pressure);
• diabetes;
• sarcoidosis;
• a brain tumor;
• swelling of the parotid gland.

Traumatic events involving the face or skull can also be associated with the onset of Bell's palsy.

Bell's palsy is not a condition associated with stroke or transient ischemic attack (TIA).

Affected populations

Bell's palsy is a fairly common condition that affects men and women in equal numbers. According to various estimates, 25-35 out of 100,000 people suffer from Bell's palsy. Approximately 40,000 people are diagnosed with the disease each year.

Bell's palsy is more common in older people than in children, but the disorder can affect people of any age. However, pregnant women or people with diabetes or upper respiratory disease are more likely to be affected than the general population.

Diagnostics

Diagnosis is based on physical examination, in particular when observing the characteristic distortion of the face and the inability to move the muscles on the affected side; however, there is no laboratory test that can unequivocally confirm the disorder. Therefore, other possible causes of facial paralysis must be ruled out.

As a rule, various clinical studies are required, both laboratory (blood tests) and instrumental tests (for example, magnetic resonance imaging (MRI) and computed tomography (CT)) to check for fractures or tumors that may have damaged VII cranial nerve.

The test that provides significant help is electromyography (EMG), thanks to this test you can check for the presence of nerve lesions and, in case of a positive result, determine the degree of damage to the facial nerve.

Symptomatic Disorders

Symptoms of the following disorders may be similar to those of Bell's palsy. Comparisons can be useful for differential diagnosis:

• Acoustic neuroma - benign tumor of the 8th cranial nerve. This nerve lies in the internal auditory canal. Compression of this nerve by a tumor leads to early symptoms of an acoustic neuroma, a ringing sound in the ear (noise in ears) and / or hearing loss. The associated compression of the other facial nerve (7th cranial nerve) can cause muscle weakness if the trigeminal nerve (5th cranial nerve) is compressed - facial numbness occurs. Spread of the tumor to different areas can lead to impaired ability to coordinate movements of the legs and arms (ataxia), numbness in the mouth, slurred speech (dysarthria) and / or hoarseness.
• Myasthenia gravis - a chronic neuromuscular disease characterized by muscle weakness. Initially, the muscles of the mouth, lips, tongue and vocal apparatus are most affected. Early symptoms of the disorder may include difficulty speaking, chewing, and / or swallowing; drooping of the upper eyelid (ptosis), double vision (diplopia). When symptoms occur on one side (unilateral), the disorder resembles Bell's palsy. As a result, muscle weakness occurs in the arms and legs, leading to generalized physical weakness.
• Ramsey-Hunt Syndrome (SRS), also known as geniculate ganglionitis, is a rare neurological disorder characterized by paralysis of certain facial nerves (facial paralysis), a rash affecting the ear or mouth, ringing in ears. Ramsey-Hunt syndrome is caused by the varicella-zoster virus, the same virus that causes chickenpox in children and shingles in adults. In cases of Ramsey-Hunt syndrome, the previously dormant varicella-zoster virus reactivates and spreads to the facial nerves. Those affected experience hearing loss or severe ear pain.

Treatment

Bell's palsy is treated differently for each patient:

• Some cases are mild and do not require treatment, as symptoms tend to regress spontaneously within two weeks.
• In other cases, medications and / or other therapeutic measures are used; when the exact cause of the paralysis (eg, infection) can be traced, it is clear that a specific treatment will be helpful.

Recent studies have shown that cortisone drugs can reduce inflammation and swelling and are therefore effective and helpful in treating Bell's palsy. Other medicines such as acyclovirused to fight herpes infection can shorten the course of the disease in certain cases. Pain relieverssuch as aspirin, acetaminophen, or ibuprofen may relieve pain.

Another fundamental factor in treatment is eye protection: The disorder can interfere with the natural the ability of the eye to hydrate, leaving the precious organ exposed to dryness and subsequent irritation. Therefore, it is important to keep the eye lubricated (eg with artificial tears) and to protect it from dust and injury, especially at night.

Other treatments, such as physical therapy, facial massage, or acupuncture, can improve facial nerve function and relieve pain.

Decompression surgery to relieve pressure on the nerve remains controversial and is rarely recommended; in rare cases, cosmetic or reconstructive surgery may be required to reduce facial blemishes and repair some damage, such as a non-closing eyelid or a slanted smile.

Forecast

The prognosis for people with Bell's palsy is generally good. The degree of nerve damage determines the degree of recovery. The improvement is gradual and the recovery time varies. With or without treatment, most patients begin to recover 2 weeks after the first symptoms, and most recover completely, returning to normal work within 3-6 months. For some, however, symptoms may last longer.

In some cases, symptoms may never go away completely.

In rare cases, the disorder recurs either on the same or on the opposite side of the face.