Bell's palsy
Overview
Bell's palsy (BP) is a kind of facial paralysis that causes an inability to control the facial muscles on the afflicted side of the face for a short period of time. The severity of the symptoms might range from minor to severe. Muscle twitching, weakness, or entire loss of capacity to move one or, in rare situations, both sides of the face are examples of symptoms.
Other symptoms include eyelid drooping, a change in taste, and soreness around the ear. Symptoms usually appear within 48 hours. Bell's palsy can cause hyperacusis, which is a heightened sensitivity to sound.
It is uncertain what causes Bell's palsy. Diabetes, a recent upper respiratory tract infection, and pregnancy are all risk factors. It is caused by cranial nerve VII impairment (the facial nerve). Many people assume that this is the outcome of a viral infection that causes edema. The look of a person is used to make a diagnosis, and other alternative explanations are ruled out. Brain tumors, strokes, Ramsay Hunt syndrome type 2, myasthenia gravis, and Lyme disease are among illnesses that can induce facial paralysis.
The ailment usually improves on its own, with most people achieving normal or near-normal function. Corticosteroids have been shown to enhance results, whereas antiviral drugs may provide a little advantage. Eye drops or an eyepatch should be used to keep the eye from drying out. Surgery is often not advised. Typically, symptoms of improvement appear within 14 days, with total recovery occurring within six months. Some people may not recover entirely or may have recurrence of symptoms.
The most prevalent cause of one-sided facial nerve paralysis is Bell's palsy (70 %). It affects 1 to 4 people out of every 10,000 each year. Approximately 1.5 % is afflicted at some time in their life. It most typically affects adults between the ages of 15 and 60. Males and females are equally impacted.
Epidemiology of Bell's palsy
The yearly incidence is 15 to 20 instances per 100,000 people, with 40,000 new cases per year, and the lifetime risk is one in sixty. The recurrence rate ranges from 8% and 12%. Even if no therapy is given, 70% of patients will recover completely. Palsy has no gender or racial preference, and it can develop at any age, but it is more common in middle and late life, with the median age of onset at 40 years. Diabetes, pregnancy, preeclampsia, obesity, and hypertension are all risk factors.
Pathophysiology of Bell's palsy
Bell's palsy is caused by a dysfunction of the facial nerve (cranial nerve VII), which controls the facial muscles. The inability to move the muscles of facial expression characterizes facial palsy. The paralysis is infranuclear/lower motor neuron in nature.
It is considered that when the facial nerve is inflamed, pressure is created on the nerve where it exits the skull within its bony canal (the stylomastoid foramen), preventing neurological impulses from being sent or injuring the nerve. Patients with facial palsy who have an underlying etiology are not considered to have Bell's palsy.
Tumors, meningitis, stroke, diabetes mellitus, head trauma, and cranial nerve inflammatory conditions are all possible causes of facial paralysis (sarcoidosis, brucellosis, etc.). The neurologic findings in these disorders are seldom limited to the facial nerve. Babies with facial palsy can be born. Bilateral facial palsy has been linked to acute HIV infection in a few individuals.
Endoneurial fluid sample has been used in certain studies to identify the herpes simplex virus type 1 (HSV-1) in the majority of patients classified as Bell's palsy. Other studies, on the other hand, found HSV-1 in 31 instances (18% of the total of 176 cases classified as Bell's palsy) and herpes zoster in 45 cases out of a total of 176 cases diagnosed as Bell's palsy (26%).
Furthermore, HSV-1 infection is linked to nerve demyelination. This nerve damage process differs from the previous one in that nerve damage is caused by edema, swelling, and compression of the nerve in the small bone canal. Demyelination may be produced indirectly by an unknown immune response rather than directly by the infection.
Causes of Bell's palsy
It is uncertain what causes Bell's palsy. Diabetes, a recent upper respiratory tract infection, and pregnancy are all risk factors.
Some viruses, such as the herpes simplex virus varicella zoster virus and the Epstein–Barr virus, are considered to cause a chronic (or latent) infection without causing symptoms. The reactivation of a previously latent viral infection has been proposed as the etiology of acute Bell's palsy. Trauma, environmental conditions, and metabolic or emotional issues might all cause this new activation.
In 4–14% of instances, familial inheritance has been discovered. There may possibly be a link with migraines.
In December 2020, the U.S. FDA recommended that recipients of the Pfizer and Moderna COVID-19 vaccines should be monitored for symptoms of Bell's palsy after several cases were reported among clinical trial participants, though the data were not sufficient to determine a causal link.
Signs and symptoms of Bell's palsy
Bell's palsy is distinguished by a one-sided facial droop that appears within 72 hours. It can occur on both sides in rare situations (1%), resulting in complete facial paralysis.
Blinking and closing the eyes, smiling, frowning, lacrimation, salivation, flaring nostrils, and lifting the brows are all controlled by the facial nerve. Taste sensations are also transmitted from the anterior two-thirds of the tongue via the chorda tympani nerve (a branch of the facial nerve). As a result, persons with Bell's palsy may have a loss of taste sensation in the front third of the tongue on the afflicted side.
Although the facial nerve innervates the stapedius muscle of the middle ear (through the tympanic branch), sound sensitivity, which causes normal sounds to be heard as extremely loud (hyperacusis), and dysacusis are conceivable but seldom clinically apparent.
Although Bell's palsy is classified as a mononeuritis (involving only one nerve), patients may experience "myriad neurological symptoms" such as "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."
How is Bell's palsy diagnosed?
The evaluation is guided by the history and physical examination. To characterize the degree of facial nerve weakness, the House-Brackmann Facial Nerve Grading System might be employed. This grading system ranges from I (no weakness) to VI (complete weakness). There are no needed lab or radiographic testing if the presentation is compatible with BP.
If there are any uncommon traits, individuals should be investigated for an underlying cause of their symptoms. Similarly, Lyme disease testing is predicated on a history of tick-borne illness. Routine Lyme disease testing is not advised in the absence of additional symptoms of the disease, such as a history of a tick bite, skin rash, or arthritis.
Diabetic testing should not be done since facial nerve palsy does not qualify as diabetic neuropathy. There is no agreement on the best time to have Lyme disease imaging, however most sites advocate getting it done after two months of no improvement in the facial palsy.
Magnetic Resonance Imaging (MRI) is the preferred imaging modality. A facial nerve MRI can reveal inflammation while also ruling out other disorders such as schwannoma, hemangioma, or a space-occupying lesion.
In patients with severe BP, nerve conduction tests and electromyography (EMG) may aid in determining outcomes.
EMG is used in electroneurography to measure the difference in potentials generated by the face muscles on both sides.
Auditory evoked potentials and audiography should be done if hearing loss is suspected.
Differential diagnosis of Bell's palsy
When facial paralysis occurs, many individuals mistake it for a stroke symptom; however, there are a few significant distinctions. A stroke is typically accompanied by a few other symptoms, such as numbness or paralysis in the arms and legs. In addition, unlike Bell's palsy, a stroke frequently allows patients to control the top half of their faces. A person who has had a stroke will generally have some wrinkling of the brow.
Lyme disease accounts for around 25% of occurrences of facial palsy in places where it is prevalent. Lyme disease is most frequent in New England and the Mid-Atlantic states, as well as parts of Wisconsin and Minnesota. An expanding rash that may be accompanied by headaches, body aches, lethargy, or fever is usually the initial manifestations of roughly 80% of Lyme infections, usually one or two weeks following a tick bite.
Facial palsy arises several weeks later in up to 10–15 % of Lyme infections and may be the first symptom of disease identified because the Lyme rash does not itch and is not painful. Based on a recent history of outdoor activities in likely tick habitats during warmer months, a recent history of rash or symptoms such as headache and fever, and whether the palsy affects both sides of the face (much more common in Lyme than in Bell's palsy), the likelihood that the facial palsy is caused by Lyme disease should be estimated.
If that likelihood is greater than a negligible, a serological test for Lyme disease should be done, and if it exceeds 10%, empiric antibiotic therapy without corticosteroids should be commenced and re-evaluated following completion of Lyme disease laboratory testing. Corticosteroids have been shown to have a negative impact on the outcome of facial palsy induced by Lyme disease.
Involvement of the facial nerve in herpes zoster virus infections is one condition that may be difficult to rule out in the differential diagnosis. The development of tiny blisters, or vesicles, on the external ear, considerable discomfort in the jaw, ear face, and/or neck, and hearing problems are the main distinctions in this disorder, however these findings may occasionally be absent (zoster sine herpete).
Ramsay Hunt syndrome type 2 is defined as the reactivation of an existing herpes zoster infection that results in facial paralysis in a Bell's palsy pattern. Bell's Palsy patients have a substantially better prognosis than Ramsay Hunt Syndrome Type 2 patients.
Treatment of Bell's palsy
Steroids have been demonstrated to improve recovery in Bell's palsy, although antivirals have not. Eye protection is necessary for people who are unable to close their eyes. Pregnancy management is comparable to non-pregnant management.
Steroids:
Prednisone and other corticosteroids, such as prednisone, boost recovery after 6 months and are hence advised. Early therapy (within 3 days after onset) is required for benefit, with a 14 % higher chance of recovery.
Antivirals:
According to one study, antivirals (such as aciclovir) are unsuccessful in improving Bell's palsy recovery beyond steroids alone in mild to severe illness. Another study discovered a benefit when paired with corticosteroids, although the data was not strong enough to support this result.
It is also uncertain in severe illness. One 2015 study discovered no impact, regardless of intensity. Another study found a minor advantage when combined with steroids.
They are frequently recommended because to a possible relationship between Bell's palsy and the herpes simplex and varicella zoster viruses. There is still a chance that they will result in a benefit of less than 7%, which has not been ruled out.
Eye protection:
When Bell's palsy impairs the blink reflex and prevents the eye from closing completely, it is suggested to apply tear-like eye drops or eye ointments often during the day, and to shield the eyes with patches or tape them shut during sleep and rest times.
Physiotherapy:
Physiotherapy can assist some people with Bell's palsy maintain muscular tone in the damaged face muscles and activate the facial nerve. Prior to recovery, it is critical to do muscular re-education exercises and soft tissue treatments to assist avoid lasting contractures of the paralyzed face muscles. Heat can be applied to the afflicted side of the face to alleviate discomfort. There is no high-quality data to support the role of electrical stimulation in the treatment of Bell's palsy.
Surgery:
Surgery may be able to improve results in patients who have not recovered from facial nerve palsy. There are several approaches available. Smile surgery, also known as smile reconstruction, is a surgical treatment that can help persons with facial nerve paralysis regain their smile. Hearing loss is one of the side effects that affects 3–15 % of persons. After evaluating relevant randomized and quasi-randomized controlled studies, a Cochrane review was unable to identify whether early surgery is useful or detrimental. The American Academy of Neurology did not advocate surgical decompression.
Alternative medicine:
Because the current research are of poor quality, the effectiveness of acupuncture remains uncertain (poor primary study design or inadequate reporting practices). In severe illness, there is very preliminary evidence for hyperbaric oxygen treatment.
Possible consequences & prognosis of Bell's palsy
Even those who do not undergo therapy, most persons with Bell's palsy begin to restore normal facial function within 3 weeks. In a 1982 research, when no therapy was available, 85 percent of 1,011 patients exhibited early symptoms of recovery within three weeks after beginning. Recovery happened 3–6 months later for the remaining 15%.
After at least one year of follow-up or until restoration, more than two-thirds (71%) of all patients had recovered completely. Only 4% of patients had a decent recovery, while the rest had a bad recovery. Another study discovered that partial palsies almost typically disappear completely within a month. Patients who regain mobility during the first two weeks almost often recover completely.
When remission does not occur until the third or later week, a much higher proportion of individuals have sequelae. A third research discovered that young patients, those under the age of 10, had a better prognosis, while patients over the age of 61 had a worse prognosis.
Persistent loss of taste (ageusia), chronic facial spasm, face discomfort, and corneal infections are all serious potential repercussions of the illness. Another issue might emerge if the injured facial nerve regenerates incompletely or incorrectly. The nerve can be viewed as a collection of smaller individual nerve connections that branch out to their respective destinations.
Nerves are normally able to follow the original course to their destination after regeneration, but certain nerves may deviate, resulting in a condition known as synkinesis. Regrowth of nerves controlling muscles related to the eye, for example, may sidetrack and regenerate connections reaching the muscles of the mouth. In this way, the movement of one impacts the movement of the other. When a person shuts one eye, the corner of the mouth raises instinctively.
Around 9% of people have chronic issues after Bell's palsy, most often synkinesis, spasm, contracture, tinnitus or hearing loss during facial movement, or crocodile-tear syndrome. This condition, also known as gustatolacrimal reflex or Bogorad's syndrome, causes the patient to cry when eating. This is assumed to be linked to poor facial nerve regeneration, a branch of which controls the lacrimal and salivary glands. Gustatorial sweating is also possible.
Conclusion
Bell palsy (BP) is the most frequent peripheral paralysis of the seventh cranial nerve, having a sudden and unilateral onset. The most prevalent cause of one-sided facial nerve paralysis is Bell's palsy (70 %). It affects 1 to 4 people out of every 10,000 each year. Approximately 1.5 % is afflicted at some time in their life. It most typically affects adults between the ages of 15 and 60. Males and females are equally impacted.
The diagnosis is one of exclusion, and it is usually determined on the basis of a physical exam. The facial nerve has branches that run intracranially, intratemporally, and extratemporally. The facial nerve is responsible for motor and parasympathetic functions, as well as taste sensation in the anterior two-thirds of the tongue. It also regulates the salivary and lacrimal glands. The upper and lower face muscles are controlled by the motor function of the peripheral facial nerve. As a result, diagnosing BP necessitates paying close attention to the strength of the forehead muscles.
The condition usually improves on its own, with most people achieving normal or near-normal function. Corticosteroids have been shown to enhance results, whereas antiviral medicines may provide a little advantage. Eye drops or an eyepatch should be used to keep the eye from drying out.
Surgery is often not advised. Typically, symptoms of improvement appear within 14 days, with total healing occurring within six months. Some people may not recover entirely or may have recurrence of symptoms.