What is Bell's Palsy?
Bell's palsy is a form of facial paralysis resulting from a dysfunction of the cranial nerve VII (the facial nerve) causing an inability to control facial muscles on the affected side. Several conditions can cause facial paralysis, e.g., brain tumor, stroke, myasthenia gravis, and Lyme disease. However, if no specific cause can be identified, the condition is known as Bell's palsy. Named after Scottish anatomist Charles Bell, who first described it, Bell's palsy is the most common acute mononeuropathy (disease involving only one nerve) and is the most common cause of acute facial nerve paralysis (>80%). Bell's palsy is defined as an idiopathic unilateral facial nerve paralysis, usually self-limiting. The hallmark of this condition is a rapid onset of partial or complete paralysis that often occurs overnight. In rare cases (<1%), it can occur bilaterally resulting in total facial paralysis.
Signs and symptoms
The onset of paralysis is sudden with Bell’s palsy, and can worsen during the early stages. Symptoms will usually manifest and peak within 2-3 days, although it can take as long as 2 weeks. Common symptoms include, but are not limited to:
- Muscle weakness or paralysis
- Overall droopy facial appearance
- Impossible or difficult to blink
- Difficulty speaking
- Difficulty eating and drinking
- Nose runs
- Nose is constantly stuffed
- Forehead wrinkles disappear
- Sensitivity to sound
- Excess or reduced salivation
- Facial swelling
- Diminished or distorted taste
There are also some eye related symptoms, which include but are not limited to:
- Difficulty closing the eye
- Sensitivity to light
- Lower eyelid droop
- Tears fail to coat cornea
- Brow droop
- Excessive tearing
- Lack of tears
Bell's palsy is characterized by facial drooping on the affected half, due to malfunction of the facial nerve (VII cranial nerve), which controls the muscles of the face. Facial palsy is typified by inability to control movement in the facial muscles.
The facial nerves control a number of functions, such as blinking and closing the eyes, smiling, frowning, lacrimation, salivation, flaring nostrils and raising eyebrows. They also innervate the stapedial (stapes) muscles of the middle ear and carry taste sensations from the anterior two-thirds of the tongue. Because both the nerve to the stapedius and the chorda tympani nerve (taste) are branches of the facial nerve, patients with Bell's palsy may present with hyperacus is or loss of taste sensation in the anterior 2/3 of the tongue.
Clinicians should determine whether the forehead muscles are spared. Due to an anatomical peculiarity, forehead muscles receive innervation from both sides of the brain. The forehead can therefore still be wrinkled by a patient whose facial palsy is caused by a problem in one of the hemispheres of the brain (central facial palsy). If the problem resides in the facial nerve itself (peripheral palsy) all nerve signals are lost on the ipsilateral (same side of the lesion) half side of the face, including to the forehead (contralateral forehead still wrinkles).
Although defined as a mononeuritis (involving only one nerve), patients diagnosed with Bell’s palsy may have "myriad neurological symptoms" including "facial tingling, moderate or severe headache/neck pain, memory problems, balance problems, ipsilateral limb paresthesias, ipsilateral limb weakness, and a sense of clumsiness" that are "unexplained by facial nerve dysfunction.
Exercises for Bell’s Palsy
While there is no high quality evidence to support significant benefit or harm from any physical therapy for idiopathic facial paralysis, there is some evidence that tailored facial exercises can help to improve facial function, mainly for people with moderate paralysis and chronic cases. There is also some evidence that facial exercises reduce sequelae in acute cases.
While cases vary, you are likely to deal with residuals such as: synkinesis, cross-wiring, hypertonic muscles, and spasms if you have suffered from Bell’s palsy for a longer time period. For some people, the muscles have had time to develop inappropriate movements. These movements must be unlearned, and correctly coordinated actions slowly relearned. Muscles that are holding other muscles captive have to be retrained in order to free-up other muscles to move correctly.
The basic idea is to slowly recreate the brain-to-nerve-to-muscle routine. At first, the goal is to regain the capability of doing correct movements voluntarily, while mentally focusing on the action.
But over a period of time, these movements may finally become automatic, natural movements and expressions. While it is a slow process, performing the exercises below may be beneficial.
- Sniffle, wrinkle nose, and flare nostrils
- Curl your upper lip up, and then raise and protrude the upper lip
- Try to smile without showing teeth, then smile showing teeth
- Using your index finger and thumb, pull the corners of your lips in toward the center. Slowly and smoothly push out and up into a smile. Continue the movement up to the cheekbone. Use a firm pressure
- Try to close the eye slowly and gently, without letting your mouth pull up or your eyebrow move downward
- Try to raise your eyebrows, and then hold for 10 -15 seconds. Pause, and repeat.
- Gently wink with one eye, and then try the other one. Do it to the best of your ability, and do not push it.
- Open eyes widely, but without involving your eyebrow. Stop if you see any inappropriate muscle actions.
Facial nerve: the facial nerve's nuclei are in the brainstem (they are represented in the diagram as a „θ“). Orange: nerves coming from the left hemisphere of the brain. Yellow: nerves coming from the right hemisphere of the brain. Note that the forehead muscles receive innervation from both hemispheres of the brain (represented in yellow and orange).
Bell's palsy affects each individual differently. Steroids have been shown to be effective at improving recovery while antivirals have not.
Corticosteroid such as prednisone significantly improves recovery at 6 months and are thus recommended. Early treatment (within 3 days after the onset) is necessary for benefit with a 14% greater probability of recovery.
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. There is still the possibility that they might result in a benefit less than 7% as this has not been ruled out.
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. To reduce pain, heat can be applied to the affected side of the face.
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 may restore the smile for people with facial nerve paralysis. It is unknown if early surgery is beneficial or harmful. Adverse effects include hearing loss which occurs in 3-15% of people.
The efficacy of acupuncture remains unknown because the available studies are of low quality (poor primary study design or inadequate reporting practices).
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.
N.B. Bell’s palsy is not a reportable disease, and there are no established registries for patients with this diagnosis, which complicates precise estimation.
Most people with Bell's palsy start to regain normal facial function within 3 weeks—even those who do not receive treatment. In a 1982 study, when no treatment was available, of 1,011 patients, 85% showed first signs of recovery within 3 weeks after onset. For the other 15%, recovery occurred 3–6 months later. After a follow-up of at least 1 year or until restoration, complete recovery had occurred in more than two-thirds (71%) of all patients. Recovery was judged moderate in 12% and poor in only 4% of patients. Another study found that incomplete palsies disappear entirely, nearly always in the course of one month. The patients who regain movement within the first two weeks nearly always remit entirely. When remission does not occur until the third week or later, a significantly greater part of the patients develop sequelae. A third study found a better prognosis for young patients, aged below 10 years old, while the patients over 61 years old presented a worse prognosis.
Major complications of the condition are chronic loss of taste (ageusia), chronic facial spasm, facial pain and corneal infections. To prevent the latter, the eyes may be protected by covers, or taped shut during sleep and for rest periods, and tear-like eye drops or eye ointments may be recommended, especially for cases with complete paralysis. Where the eye does not close completely, the blink reflex is also affected, and care must be taken to protect the eye from injury.
Another complication can occur in case of incomplete or erroneous regeneration of the damaged facial nerve. The nerve can be thought of as a bundle of smaller individual nerve connections that branch out to their proper destinations. During regrowth, nerves are generally able to track the original path to the right destination - but some nerves may sidetrack leading to a condition known as synkinesis. For instance, regrowth of nerves controlling muscles attached to the eye may sidetrack and also regrow connections reaching the muscles of the mouth. In this way, movement of one also affects the other. For example, when the person closes the eye, the corner of the mouth lifts involuntarily.
Around 9% of patients have some sort of sequelae (an after effect of disease, condition, or injury) after Bell's palsy, typically the synkinesis already discussed, or spasm, contracture, tinnitus and/or hearing loss during facial movement or crocodile tear syndrome. This is also called gustatolacrimal reflex or Bogorad’s Syndrome and involves the sufferer shedding tears while eating. This is thought to be due to faulty regeneration of the facial nerve, a branch of which controls the lacrimal and salivary glands. Gustatorial sweating can also occur.