Bell's Palsy

What is Bell's Palsy?

Named after Scottish anatomist Charles Bell, who first described it, Bell’s palsy is a non-specific diagnosis given to facial paralysis when all of the specific causes such as a brain tumor, Lyme Disease, or stroke have been ruled out. In most cases the paralysis affects one side of the face, giving it slack muscle tone and a characteristic droop along the eye and mouth.Bell's palsy is a form of temporary facial paralysis resulting from damage or trauma to one of the facial nerves.  It is the most common cause of facial paralysis. Generally, Bell's palsy affects only one of the paired facial nerves and one side of the face, however, in rare cases, it can affect both sides.  Symptoms of Bell's palsy usually begin suddenly and reach their peak within 48 hours.  Symptoms vary from person to person and can range in severity from mild weakness to total paralysis.  These symptoms include twitching, weakness, or paralysis, drooping eyelid or corner of the mouth, drooling, dry eye or mouth, impairment of taste, and excessive tearing in the eye. Bell’s palsy often causes significant facial distortion. Most scientists believe that a viral infection such as viral meningitis or the common cold sore virus -- herpes simplex-- can cause the disorder when the facial nerve swells and becomes inflamed in reaction to the infection. What causes Bell's palsy? The cause of Bell's palsy is not clear. Most cases are thought to be caused by the herpes virus that causes cold sores.In most cases of Bell's palsy, the nerve that controls muscles on one side of the face is damaged by inflammation.Many health problems can cause weakness or paralysis of the face. If a specific reason cannot be found for the weakness, the condition is called Bell's palsy.

   

Facial Nerve Anatomy

 The facial nerve controls the muscles that move the eyebrows, close the eyes, and move the mouth and lips. It also controls the tear glands, one of the salivary glands, and the taste buds in the front of the tongue.

 Electrochemical signals are relayed between the brain and many facial muscles by 7000 nerve fibers that comprise the     facial nerve. When the facial nerve is damaged, as in Bell's palsy, the action of each nerve fiber is disrupted. Because the facial nerve controls several functions, several symptoms occur.

 Diagnostic test:

Diagnosis of Bell's Palsy

A diagnosis of Bell's palsy is often based on symptoms and by ruling out other disorders. Other conditions that may cause facial paralysis include facial tumors, certain cancers, and autoimmune diseases. The physician can usually exclude other disorders by taking the patient's history of symptoms, and by examining the head, neck, ears, and eyes.

During the physical examination, the doctor observes the patient's range of movement in different parts of the face (e.g., raising and lowering the eyebrows, closing both eyes). If one eyebrow cannot be raised or can only be lifted slightly, it suggests that one side of the face is weaker. Similarly, if one eye cannot be closed tightly, it indicates a problem with the controlling muscles. If paralysis or muscle weakness is noted in another part of the body, Bell's palsy may be ruled out through diagnostic testing.

Imaging tests such as computerized tomography (CT scan) or magnetic resonance imaging (MRI scan)are used to detect infection, tumor, bone fracture, or other abnormality in and around the facial nerve.

Hearing and balance tests are used to determine if the nerve responsible for hearing is also damaged and assess injury to the inner ear. Tests can be performed to evaluate the eye's ability to produce tears. The sense of taste also can be evaluated to determine the location and severity of a facial nerve lesion.

Electromyography (EMG) assesses injury by electrically stimulating the facial nerve. Electrical current is applied to the skin over the nerve and nerve function is determined by the amount of current needed to cause contraction of the facial muscles. The test is often repeated to assess disease progression and the extent of injury.

Laboratory tests can help the physician determine the underlying cause. For example, a blood test for Lyme disease may be ordered if there is a chance that the patient was bitten by a deer tick, or a blood glucose test may be obtained to determine if the patient has undiagnosed diabetes.

                             Pathophysiology

             The pathophysiology of Bell's Palsy is not entirely clear, but is most likely related to compression of the facial nerve due to demyelination, inflammation, or ischemia (inadequate blood supply). The facial nerve is responsible for contraction of the muscles of the face in expression, lacrimation, and the senses of taste and hearing. As a result of its convoluted path through the temporal bone which is only slightly larger in diameter than itself, the 10,000 neurons that exist in the facial nerve are prone to impairment due to vascular congestion with secondary ischemia.

Pathology

It is thought that as a result of inflammation of the facial nerve, pressure is produced on the nerve where it exits the skull within its bony canal, blocking the transmission of neural signals or damaging the nerve. Patients with facial palsy for which an underlying cause can be found are not considered to have Bell's palsy per se. Possible causes include tumor, meningitis, stroke, diabetes mellitus, head trauma and inflammatory diseases of the cranial nerves (sarcoidosis,brucellosis, etc.). In these conditions, the neurologic findings are rarely restricted to the facial nerve. Babies can be born with facial palsy. In a few cases, bilateral facial palsy has been associated with acute HIV infection.

In some research the herpes simplex virus type 1 (HSV-1) was identified in a majority of cases diagnosed as Bell's palsy. This has given hope for anti-inflammatory and anti-viral drug therapy (prednisone and acyclovir). Other research however, identifies HSV-1 in only 31 cases (18 percent), herpes zoster in 45 cases (26 percent) in a total of 176 cases clinically diagnosed as Bell's Palsy. That infection with herpes simplex virus should playa major role in cases diagnosed as Bell's palsy therefore remains a hypothesis that requires further research.
In addition, the herpes simplex virus type 1 (HSV-1) infection is associated with demyelination of nerves. This nerve damage mechanism is different from the above mentioned - that oedema, swelling and compression of the nerve in the narrow bone canal is responsible for nerve damage. Demyelination may not even be directly caused by the virus, but by an unknown immune system response. The quote below captures this hypothesis and the implication for other types of treatment:
It is also possible that HSV-1 replication itself is not responsible for the damage to the facial nerves and that inhibition of HSV-1 replication by acyclovir does not prevent the progression of nerve dysfunction. Because the demyelination of facial nerves caused by HSV-1 reactivation, via an unknown immune response, is implicated in the pathogenesis of HSV-1-induced facial palsy, a new strategy of treatment to inhibit such an immune reaction may be also effective.

Treatment

Bell's palsy affects each individual differently. In patients presenting with incomplete facial palsy, where the prognosis for recovery is very good, treatment may be unnecessary. However, the more severe cases may require treatment. Patients presenting with complete paralysis, marked by an inability to close the eyes and mouth on the involved side, are usually treated, some of them with smile surgery. Early treatment (within 3 days after the onset) is necessary for therapy to be effective. Steroids have been shown to be effective at improving recovery while antivirals have not.

Steroids  

Corticosteroid such as prednisone significantly improves recovery at 6 months and are thus recommended. Antivirals Antivirals (such as acyclovir) are ineffective in improving recovery from Bell's palsy beyond steroids alone. They were however commonly prescribed due to a theoretical link between Bell's palsy and the herpes simplex and varicella zoster virus. Surgery Surgery may be able to improve outcomes in facial nerve palsy that has not recovered.  A number of different techniques exist. Smile surgery or smile reconstruction is a surgical procedure that restores the smile for people with facial nerve paralysis. Complementary therapy The efficacy of acupuncture remains unknown because the available studies are of low quality (poor primary study design or inadequate reporting practices).

Antivirals
Antivirals such us acyclovir are ineffective in improving recovery from Bell's Palsy beyond steroids alone. They were however commonly prescribed due to a theoretical link between Bell's palsy and the herpes simplex and varicella zoster virus.

Surgery
Surgery may be able to improve outcomes in facial nerve palsy that has not recovered. A number of different techniques exist. Smile surgery or smile reconstruction is a surgical procedure that restores the smile for the people with facial nerve paralysis.

Complementary Therapy
The efficacy of acupuncture remains unknown because the available studies are of low quality (poor primary study design or inadequate reporting practices).

Physiotherapy 

Physiotherapy can be beneficial to some individuals with Bell’s palsy as it helps to maintain muscle tone of the affected facial muscles and stimulate the facial nerve. It is important that muscle re-education exercises and soft tissue techniques be implemented prior to recovery in order to help prevent permanent contractures of the paralyzed facial muscles. Muscle re-education exercises are also useful in restoring normal movement. To reduce pain, heat can be applied to the affected side of the face. In individuals with unresolvedfacial nerve paralysis, transcutaneous electrical stimulation can be an effective treatment strategy.

Prognosis 

The prognosis for individuals with Bell's palsy is generally very good. The extent of nerve damage determines the extent of recovery.  With or without treatment, most individuals begin to get better within 2 weeks after the initial onset of symptoms and recover completely within 3 to 6 months.

Epidemiology

The annual incidence of Bell's palsy is about 20 per 100,000 population, and the incidence increases with age. Bell’s palsy affects about 40,000 people in the United States every year. It affects approximately 1 person in 65 during a lifetime. Familial inheritance has been found in 4–14% of cases. Bell's Palsy is three times more likely to strike pregnant women than non-pregnant women. It is also considered to be four times more likely to occur in diabetics than the general population.

A range of annual incidence rates have been reported in the literature: 15, 24, and 25-53 (all rates per 100,000 population per year). Bell’s palsy is not a reportable disease, and there are no established registries for patients with this diagnosis, which complicates precise estimation.

Risk factor:

Conditions that compromise the immune system, such as HIV, increase the risk for Bell's palsy. Patients who have diabetes are more than 4 times as likely to develop the disorder as the general population. Women who are pregnant have a 3.3 times higher risk for Bell's palsy than women who are not pregnant. During pregnancy, Bell's palsy occurs most often in the third trimester.

Other risk factors include the following:

• Bacterial infections such as Lyme disease or typhoid fever, syphillis, tuberculosis, frequent middle ear infections

• Neurological disorders such as Guillain-Barre syndrome, multiple sclerosis, and neurosarcoidosis

• Traumatic injury to the head or face

• Tumors causing nerve compression

• Viruses such as influenza (the flu), the common cold, or infectious mononucleosis

Clinical manifestation:

Sometimes you may have a cold shortly before the symptoms of Bell's palsy begin.

Symptoms most often start suddenly, but may take 2 - 3 days to show up. They do not become more severe after that. Symptoms are almost always on one side only. They may range from mild to severe.

The face will feel stiff or pulled to one side, and may look different. Other symptoms can include:

• Difficulty eating and drinking; food falls out of one side of the mouth

• Drooling due to lack of control over the muscles of the face

• Drooping of the face, such as the eyelid or corner of the mouth

• Hard to close one eye

• Problems smiling, grimacing, or making facial expressions

• Twitching or weakness of the muscles in the face

Other symptoms that may occur:

• Dry eye or mouth

• Headache

• Loss of sense of taste

• Sound that is louder in one ear (hyperacusis)

• Twitching in face

• Dizziness

• Hypersensitivity to sound

Medical management:

The objectives of management are to maintain facial muscle tone and to prevent or minimize denervation. Steroidal therapy may be initiated to reduce inflammation and edema, which reduces vascular compression and permits restoration of blood circulation to the nerve. Early administration of corticosteroids appears to diminish severity, relieve pain, and minimize denervation. Facial pain is controlled with analgesic agents or heat applied to the involved side of the face. Additional modalities may include electrical stimulation applied to the face to prevent muscle atrophy, or surgical exploration of the facial nerve. Surgery may be performed if a tumor is suspected, for surgical decompression of the facial nerve, and for surgical rehabilitation of a paralyzed face.

Nursing management:

• Provide support and reassurance.

• Provide soft diet with supplementary feedings as indicated.

• Instruct to chew on unaffected side, avoid hot fluids/foods, and perform mouth care after each meal.

• Assess facial nerve function regularly

Administer medications as ordered

• Corticosteroids: to decrease edema and pain

-Mild analgesics as necessary

• Provide special eye care to protect the cornea.

-Dark glasses (cosmetic and protective reasons) or eye shield

-Artificial tears to prevent drying of the cornea

-Ointment and eye patch at night to keep eyelid closed

Patients need reassurance that a stroke has not occurred and that spontaneous recovery occurs within 3 to 5 weeks in most patients. Teaching patients with Bell’s palsy to care for themselves at home is an important nursing priority.

Health teachings:

TEACHING EYE CARE

Because the blink reflex is diminished, the involved eye may not close completely and the needs to be protected to prevent corneal irritation and ulceration. Inform the patient of potential complications, including corneal irritation and ulceration, overflow of tears, and absence of blink reflex. Key teaching points include:

• Cover the eye with a protective shield at night.

• Apply eye ointment to keep eyelids closed during sleep.

• Close the paralyzed eyelid manually before going to sleep.

• Wear wrap-around sunglasses or goggles to decrease normal evaporation from the eye

TEACHING ABOUT MAINTAINING MUSCLE TONE

Show patient how to perform facial massage which gentle upward motion several times daily when the patient can tolerate the massage.

• Demonstrate the facial exercises, such as wrinkling the forehead, blowing out the cheeks, and whistling in an effort to prevent muscle atrophy.

• Instruct patient to avoid exposing the face to cold and drafts.

• Remind patient and family of the importance of participating in health promotion activities and recommended health screening practices