Bell's palsy
Encyclopedia
Bell's palsy is a form of facial paralysis resulting from a dysfunction of the cranial nerve VII (the facial nerve
) that results in the inability to control facial muscles on the affected side. Several conditions can cause facial paralysis, e.g., brain tumor
, stroke
, 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
.
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 palsy
that often occurs overnight. In rare cases (1%), it can occur bilaterally resulting in total facial paralysis.
It is thought that an inflammatory condition leads to swelling of the facial nerve
. The nerve travels through the skull in a narrow bone canal beneath the ear. Nerve swelling and compression in the narrow bone canal are thought to lead to nerve inhibition, damage or death. No readily identifiable cause for Bell's palsy has been found.
Corticosteroids have been found to improve outcomes while anti-viral drugs have not. Early treatment is necessary for steroids to be effective. Most people recover spontaneously and achieve near-normal to normal functions. Many show signs of improvement as early as 10 days after the onset, even without treatment.
Often the eye in the affected side cannot be closed. The eye must be protected from drying up, or the cornea
may be permanently damaged resulting in impaired vision. In some cases denture wearers experience some discomfort.
(VII cranial nerve), which controls the muscle
s of the face. Facial palsy is typified by inability to control movement in the facial muscles. The paralysis is of the infranuclear/lower motor neuron type.
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.
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).
One disease that may be difficult to exclude in the differential diagnosis
is involvement of the facial nerve in infections with the herpes zoster
virus. The major differences in this condition are the presence of small blisters, or vesicles, on the external ear and hearing disturbances, but these findings may occasionally be lacking (zoster sine herpete). Reactivation of existing herpes zoster
infection leading to facial paralysis in a Bell's palsy type pattern is known as Ramsay Hunt syndrome type 2.
Lyme disease
may produce the typical palsy, and may be easily diagnosed by looking for Lyme-specific antibodies in the blood or erythema migrans
. In endemic areas Lyme disease
may be the most common cause of facial palsy.
The degree of nerve damage can be assessed using the House-Brackmann score.
Because both the nerve to Stapedius and the chorda tympani nerve (taste) are branches of the facial nerve, patients with Bell's palsy may present with hyperacusis
or loss of taste sensation in the anterior 2/3 of the tongue.
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". This is yet an enigmatic facet of this condition.
viruses, both of the herpes family. Reactivation of an existing (dormant) viral infection has been suggested as cause behind the acute Bell's palsy. Studies suggest that this new activation could be preceded by trauma, environmental factors, and metabolic or emotional disorders, thus suggesting that stress - emotional stress, environmental stress (e.g., cold), physical stress (e.g., trauma) - in short, a host of different conditions, may trigger reactivation.
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
(zoster sine herpete) in 45 cases (26 percent) in a total of 176 cases clinically diagnosed as Bell's Palsy. That infection with herpes simplex virus should play a 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:
; by elimination of other reasonable possibilities. Therefore, by definition, no specific cause can be ascertained. Bell's palsy is commonly referred to as idiopathic
or cryptogenic
, meaning that it is due to unknown causes. Being a residual diagnostic category, the Bell's Palsy diagnosis likely spans different conditions that our current level of medical knowledge cannot distinguish. This may inject fundamental uncertainty into the discussion below of etiology
, treatment options, recovery patterns, etc. See also the section below on Other symptoms.
Studies show that a large number of patients (45%) are not referred to a specialist, which suggests that Bell’s palsy is considered by physicians to be a straightforward diagnosis that is easy to manage. A significant number of cases are misdiagnosed (Ibid.). This is unsurprising from a diagnosis of exclusion, which depends on a thorough investigation.
, 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.
such as prednisone
significantly improves recovery at 6 months and are thus recommended.
and varicella zoster virus
.
or smile reconstruction is a surgical procedure that restores the smile for people with facial nerve paralysis.
remains unknown because the available studies are of low quality (poor primary study design or inadequate reporting practices).
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 unresolved facial nerve paralysis, transcutaneous electrical stimulation can be an effective treatment strategy.
e. 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 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.
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.
, a Scot
tish surgeon. In 1829 he presented three cases at the Royal Society of London. Two cases were idiopathic and the third was due to a tumour of the parotid gland
.
Facial nerve
The facial nerve is the seventh of twelve paired cranial nerves. It emerges from the brainstem between the pons and the medulla, and controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue and oral cavity...
) that results in the inability to control facial muscles on the affected side. Several conditions can cause facial paralysis, e.g., brain tumor
Brain tumor
A brain tumor is an intracranial solid neoplasm, a tumor within the brain or the central spinal canal.Brain tumors include all tumors inside the cranium or in the central spinal canal...
, stroke
Stroke
A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...
, and Lyme disease
Lyme disease
Lyme disease, or Lyme borreliosis, is an emerging infectious disease caused by at least three species of bacteria belonging to the genus Borrelia. Borrelia burgdorferi sensu stricto is the main cause of Lyme disease in the United States, whereas Borrelia afzelii and Borrelia garinii cause most...
. However, if no specific cause can be identified, the condition is known as Bell's palsy. Named after Scottish anatomist Charles Bell
Charles Bell
Sir Charles Bell was a Scottish surgeon, anatomist, neurologist and philosophical theologian.His three older brothers included John Bell , also a noted surgeon and writer; and the advocate George Joseph Bell .-Life:...
, who first described it, Bell's palsy is the most common acute mononeuropathy
Peripheral neuropathy
Peripheral neuropathy is the term for damage to nerves of the peripheral nervous system, which may be caused either by diseases of or trauma to the nerve or the side-effects of systemic illness....
(disease involving only one nerve
Nerve
A peripheral nerve, or simply nerve, is an enclosed, cable-like bundle of peripheral axons . A nerve provides a common pathway for the electrochemical nerve impulses that are transmitted along each of the axons. Nerves are found only in the peripheral nervous system...
) and is the most common cause of acute facial nerve paralysis
Acute facial nerve paralysis
Facial nerve paralysis is a common problem that involves the paralysis of any structures innervated by the facial nerve. The pathway of the facial nerve is long and relatively convoluted, and so there are a number of causes that may result in facial nerve paralysis...
.
Bell's palsy is defined as an idiopathic
Idiopathic
Idiopathic is an adjective used primarily in medicine meaning arising spontaneously or from an obscure or unknown cause. From Greek ἴδιος, idios + πάθος, pathos , it means approximately "a disease of its own kind". It is technically a term from nosology, the classification of disease...
unilateral facial nerve paralysis, usually self-limiting. The hallmark of this condition is a rapid onset of partial or complete palsy
Palsy
In medicine, palsy is the paralysis of a body part, often accompanied by loss of sensation and by uncontrolled body movements, such as shaking. Medical conditions involving palsy include cerebral palsy , brachial palsy , and Bell's palsy ....
that often occurs overnight. In rare cases (1%), it can occur bilaterally resulting in total facial paralysis.
It is thought that an inflammatory condition leads to swelling of the facial nerve
Facial nerve
The facial nerve is the seventh of twelve paired cranial nerves. It emerges from the brainstem between the pons and the medulla, and controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue and oral cavity...
. The nerve travels through the skull in a narrow bone canal beneath the ear. Nerve swelling and compression in the narrow bone canal are thought to lead to nerve inhibition, damage or death. No readily identifiable cause for Bell's palsy has been found.
Corticosteroids have been found to improve outcomes while anti-viral drugs have not. Early treatment is necessary for steroids to be effective. Most people recover spontaneously and achieve near-normal to normal functions. Many show signs of improvement as early as 10 days after the onset, even without treatment.
Often the eye in the affected side cannot be closed. The eye must be protected from drying up, or the cornea
Cornea
The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. Together with the lens, the cornea refracts light, with the cornea accounting for approximately two-thirds of the eye's total optical power. In humans, the refractive power of the cornea is...
may be permanently damaged resulting in impaired vision. In some cases denture wearers experience some discomfort.
Signs and symptoms
Bell's palsy is characterized by facial drooping on the affected half, due to malfunction of the facial nerveFacial nerve
The facial nerve is the seventh of twelve paired cranial nerves. It emerges from the brainstem between the pons and the medulla, and controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue and oral cavity...
(VII cranial nerve), which controls the muscle
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
s of the face. Facial palsy is typified by inability to control movement in the facial muscles. The paralysis is of the infranuclear/lower motor neuron type.
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
Middle ear
The middle ear is the portion of the ear internal to the eardrum, and external to the oval window of the cochlea. The mammalian middle ear contains three ossicles, which couple vibration of the eardrum into waves in the fluid and membranes of the inner ear. The hollow space of the middle ear has...
and carry taste sensations from the anterior two-thirds of the tongue.
Clinicians should determine whether the forehead
Forehead
For the Arsenal striker see GervinhoIn human anatomy, the forehead is the fore part of the head. It is, formally, an area of the head bounded by three features, two of the skull and one of the scalp. The top of the forehead is marked by the hairline, the edge of the area where hair on the scalp...
muscles are spared. Due to an anatomical peculiarity, forehead muscles receive innervation from both sides of the brain
Human brain
The human brain has the same general structure as the brains of other mammals, but is over three times larger than the brain of a typical mammal with an equivalent body size. Estimates for the number of neurons in the human brain range from 80 to 120 billion...
. 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
Central facial palsy
Central facial palsy, is a symptom or finding characterized by paralysis or paresis of the lower half of one side of the face...
). If the problem resides in the facial nerve itself (peripheral palsy
Peripheral neuropathy
Peripheral neuropathy is the term for damage to nerves of the peripheral nervous system, which may be caused either by diseases of or trauma to the nerve or the side-effects of systemic illness....
) 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).
One disease that may be difficult to exclude in the differential diagnosis
Differential diagnosis
A differential diagnosis is a systematic diagnostic method used to identify the presence of an entity where multiple alternatives are possible , and may also refer to any of the included candidate alternatives A differential diagnosis (sometimes abbreviated DDx, ddx, DD, D/Dx, or ΔΔ) is a...
is involvement of the facial nerve in infections with the herpes zoster
Herpes zoster
Herpes zoster , commonly known as shingles and also known as zona, is a viral disease characterized by a painful skin rash with blisters in a limited area on one side of the body, often in a stripe...
virus. The major differences in this condition are the presence of small blisters, or vesicles, on the external ear and hearing disturbances, but these findings may occasionally be lacking (zoster sine herpete). Reactivation of existing herpes zoster
Herpes zoster
Herpes zoster , commonly known as shingles and also known as zona, is a viral disease characterized by a painful skin rash with blisters in a limited area on one side of the body, often in a stripe...
infection leading to facial paralysis in a Bell's palsy type pattern is known as Ramsay Hunt syndrome type 2.
Lyme disease
Lyme disease
Lyme disease, or Lyme borreliosis, is an emerging infectious disease caused by at least three species of bacteria belonging to the genus Borrelia. Borrelia burgdorferi sensu stricto is the main cause of Lyme disease in the United States, whereas Borrelia afzelii and Borrelia garinii cause most...
may produce the typical palsy, and may be easily diagnosed by looking for Lyme-specific antibodies in the blood or erythema migrans
Erythema migrans
Erythema chronicum migrans refers to the rash often seen in the early stage of Lyme disease. It can appear anywhere from one day to one month after a tick bite. This rash does not represent an allergic reaction to the bite, but rather an actual skin infection with the Lyme bacteria, Borrelia...
. In endemic areas Lyme disease
Lyme disease
Lyme disease, or Lyme borreliosis, is an emerging infectious disease caused by at least three species of bacteria belonging to the genus Borrelia. Borrelia burgdorferi sensu stricto is the main cause of Lyme disease in the United States, whereas Borrelia afzelii and Borrelia garinii cause most...
may be the most common cause of facial palsy.
The degree of nerve damage can be assessed using the House-Brackmann score.
Because both the nerve to Stapedius and the chorda tympani nerve (taste) are branches of the facial nerve, patients with Bell's palsy may present with hyperacusis
Hyperacusis
Hyperacusis is a health condition characterized by an over-sensitivity to certain frequency ranges of sound...
or loss of taste sensation in the anterior 2/3 of the tongue.
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". This is yet an enigmatic facet of this condition.
Cause
Some viruses are thought to establish a persistent (or latent) infection without symptoms, e.g., the varicella-zoster virus and Epstein-BarrEpstein-Barr virus
The Epstein–Barr virus , also called human herpesvirus 4 , is a virus of the herpes family and is one of the most common viruses in humans. It is best known as the cause of infectious mononucleosis...
viruses, both of the herpes family. Reactivation of an existing (dormant) viral infection has been suggested as cause behind the acute Bell's palsy. Studies suggest that this new activation could be preceded by trauma, environmental factors, and metabolic or emotional disorders, thus suggesting that stress - emotional stress, environmental stress (e.g., cold), physical stress (e.g., trauma) - in short, a host of different conditions, may trigger reactivation.
Pathology
Inflammation
Inflammation is part of the complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants. Inflammation is a protective attempt by the organism to remove the injurious stimuli and to initiate the healing process...
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
Tumor
A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...
, meningitis
Meningitis
Meningitis is inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges. The inflammation may be caused by infection with viruses, bacteria, or other microorganisms, and less commonly by certain drugs...
, stroke
Stroke
A stroke, previously known medically as a cerebrovascular accident , is the rapidly developing loss of brain function due to disturbance in the blood supply to the brain. This can be due to ischemia caused by blockage , or a hemorrhage...
, diabetes mellitus
Diabetes mellitus
Diabetes mellitus, often simply referred to as diabetes, is a group of metabolic diseases in which a person has high blood sugar, either because the body does not produce enough insulin, or because cells do not respond to the insulin that is produced...
, head trauma
Head injury
Head injury refers to trauma of the head. This may or may not include injury to the brain. However, the terms traumatic brain injury and head injury are often used interchangeably in medical literature....
and inflammatory diseases of the cranial nerves (sarcoidosis
Sarcoidosis
Sarcoidosis , also called sarcoid, Besnier-Boeck disease or Besnier-Boeck-Schaumann disease, is a disease in which abnormal collections of chronic inflammatory cells form as nodules in multiple organs. The cause of sarcoidosis is unknown...
, brucellosis
Brucellosis
Brucellosis, also called Bang's disease, Crimean fever, Gibraltar fever, Malta fever, Maltese fever, Mediterranean fever, rock fever, or undulant fever, is a highly contagious zoonosis caused by ingestion of unsterilized milk or meat from infected animals or close contact with their secretions...
, 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
Acute HIV infection
Acute HIV infection or primary HIV infection is the second stage of HIV infection. It occurs after the incubation stage, before the latency stage and the potential AIDS succeeding the latency stage....
.
In some research the herpes simplex virus
Herpes simplex virus
Herpes simplex virus 1 and 2 , also known as Human herpes virus 1 and 2 , are two members of the herpes virus family, Herpesviridae, that infect humans. Both HSV-1 and HSV-2 are ubiquitous and contagious...
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
Herpes zoster
Herpes zoster , commonly known as shingles and also known as zona, is a viral disease characterized by a painful skin rash with blisters in a limited area on one side of the body, often in a stripe...
(zoster sine herpete) in 45 cases (26 percent) in a total of 176 cases clinically diagnosed as Bell's Palsy. That infection with herpes simplex virus should play a 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
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
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.
Diagnosis
Bell's palsy is a diagnosis of exclusionDiagnosis of exclusion
A diagnosis of exclusion is a medical condition reached by a process of elimination, which may be necessary if presence cannot be established with complete confidence from examination or testing...
; by elimination of other reasonable possibilities. Therefore, by definition, no specific cause can be ascertained. Bell's palsy is commonly referred to as idiopathic
Idiopathic
Idiopathic is an adjective used primarily in medicine meaning arising spontaneously or from an obscure or unknown cause. From Greek ἴδιος, idios + πάθος, pathos , it means approximately "a disease of its own kind". It is technically a term from nosology, the classification of disease...
or cryptogenic
Cryptogenic disease
A cryptogenic disease is a disease of which the cause is unknown. It may be used in a particular case, when the nature of the patient's condition is known but the cause has not been found . The word cryptogenic also appears in the names of some disease entities, when the situation is sufficiently...
, meaning that it is due to unknown causes. Being a residual diagnostic category, the Bell's Palsy diagnosis likely spans different conditions that our current level of medical knowledge cannot distinguish. This may inject fundamental uncertainty into the discussion below of etiology
Etiology
Etiology is the study of causation, or origination. The word is derived from the Greek , aitiologia, "giving a reason for" ....
, treatment options, recovery patterns, etc. See also the section below on Other symptoms.
Studies show that a large number of patients (45%) are not referred to a specialist, which suggests that Bell’s palsy is considered by physicians to be a straightforward diagnosis that is easy to manage. A significant number of cases are misdiagnosed (Ibid.). This is unsurprising from a diagnosis of exclusion, which depends on a thorough investigation.
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 paralysisParalysis
Paralysis is loss of muscle function for one or more muscles. Paralysis can be accompanied by a loss of feeling in the affected area if there is sensory damage as well as motor. A study conducted by the Christopher & Dana Reeve Foundation, suggests that about 1 in 50 people have been diagnosed...
, marked by an inability to close the eyes and mouth on the involved side, are usually treated, some of them with smile surgery
Smile surgery
Smile surgery or smile reconstruction is a surgical procedure that restores the smile for people with facial nerve paralysis. Facial nerve paralysis is a relatively common condition with a yearly incidence of 0.25% leading to function loss of the mimic muscles. The facial nerve gives off several...
. 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
CorticosteroidCorticosteroid
Corticosteroids are a class of steroid hormones that are produced in the adrenal cortex. Corticosteroids are involved in a wide range of physiologic systems such as stress response, immune response and regulation of inflammation, carbohydrate metabolism, protein catabolism, blood electrolyte...
such as prednisone
Prednisone
Prednisone is a synthetic corticosteroid drug that is particularly effective as an immunosuppressant drug. It is used to treat certain inflammatory diseases and some types of cancer, but has significant adverse effects...
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 simplexHerpes simplex
Herpes simplex is a viral disease caused by both Herpes simplex virus type 1 and type 2 . Infection with the herpes virus is categorized into one of several distinct disorders based on the site of infection. Oral herpes, the visible symptoms of which are colloquially called cold sores or fever...
and varicella zoster virus
Varicella zoster virus
Varicella zoster virus is one of eight herpes viruses known to infect humans . It commonly causes chicken-pox in children and Herpes zoster in adults and rarely in children.-Nomenclature:...
.
Surgery
Surgery may be able to improve outcomes in facial nerve palsy that has not recovered. A number of different techniques exist. Smile surgerySmile surgery
Smile surgery or smile reconstruction is a surgical procedure that restores the smile for people with facial nerve paralysis. Facial nerve paralysis is a relatively common condition with a yearly incidence of 0.25% leading to function loss of the mimic muscles. The facial nerve gives off several...
or smile reconstruction is a surgical procedure that restores the smile for people with facial nerve paralysis.
Complementary therapy
The efficacy of acupunctureAcupuncture
Acupuncture is a type of alternative medicine that treats patients by insertion and manipulation of solid, generally thin needles in the body....
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 toneMuscle tone
In physiology, medicine, and anatomy, muscle tone is the continuous and passive partial contraction of the muscles, or the muscle’s resistance to passive stretch during resting state. It helps maintain posture, and it declines during REM sleep.-Purpose:Unconscious nerve impulses maintain the...
of the affected facial muscles
Facial muscles
The facial muscles are a group of striated muscles innervated by the facial nerve that, among other things, control facial expression. These muscles are also called mimetic muscles.-Structure:...
and stimulate the facial nerve
Facial nerve
The facial nerve is the seventh of twelve paired cranial nerves. It emerges from the brainstem between the pons and the medulla, and controls the muscles of facial expression, and functions in the conveyance of taste sensations from the anterior two-thirds of the tongue and oral cavity...
. It is important that muscle re-education exercises and soft tissue
Soft tissue
In anatomy, the term soft tissue refers to tissues that connect, support, or surround other structures and organs of the body, not being bone. Soft tissue includes tendons, ligaments, fascia, skin, fibrous tissues, fat, and synovial membranes , and muscles, nerves and blood vessels .It is sometimes...
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
Pain
Pain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...
, heat can be applied to the affected side of the face. In individuals with unresolved facial nerve paralysis, transcutaneous electrical stimulation can be an effective treatment strategy.
Prognosis
Even without any treatment, Bell's palsy tends to carry a good prognosis. 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 sequelaSequela
A sequela) is a pathological condition resulting from a disease, injury, or other trauma.Chronic kidney disease, for example, is sometimes a sequela of diabetes, and neck pain is a common sequela of whiplash or other trauma to the cervical vertebrae. Post-traumatic stress disorder may be a...
e. 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
Ageusia
Ageusia is the loss of taste functions of the tongue, particularly the inability to detect sweetness, sourness, bitterness, saltiness, and umami . It is sometimes confused with anosmia - a loss of the sense of smell...
), chronic facial spasm
Spasm
In medicine a spasm is a sudden, involuntary contraction of a muscle, a group of muscles, or a hollow organ, or a similarly sudden contraction of an orifice. It is sometimes accompanied by a sudden burst of pain, but is usually harmless and ceases after a few minutes...
, 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
Paralysis
Paralysis is loss of muscle function for one or more muscles. Paralysis can be accompanied by a loss of feeling in the affected area if there is sensory damage as well as motor. A study conducted by the Christopher & Dana Reeve Foundation, suggests that about 1 in 50 people have been diagnosed...
. 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
Synkinesis
Synkinesis is the result from miswiring of nerves after trauma. This result is manifested through involuntary muscular movements accompanying voluntary movements...
. 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 after Bell's palsy, typically the synkinesis already discussed, or spasm, contracture, tinnitus
Tinnitus
Tinnitus |ringing]]") is the perception of sound within the human ear in the absence of corresponding external sound.Tinnitus is not a disease, but a symptom that can result from a wide range of underlying causes: abnormally loud sounds in the ear canal for even the briefest period , ear...
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
Synkinesis
Synkinesis is the result from miswiring of nerves after trauma. This result is manifested through involuntary muscular movements accompanying voluntary movements...
of the facial nerve, a branch of which controls the lacrimal and salivary glands. Gustatorial sweating can also occur.
Epidemiology
The annual incidenceIncidence (epidemiology)
Incidence is a measure of the risk of developing some new condition within a specified period of time. Although sometimes loosely expressed simply as the number of new cases during some time period, it is better expressed as a proportion or a rate with a denominator.Incidence proportion is the...
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.
History
This lesion was described by Sir Charles BellCharles Bell
Sir Charles Bell was a Scottish surgeon, anatomist, neurologist and philosophical theologian.His three older brothers included John Bell , also a noted surgeon and writer; and the advocate George Joseph Bell .-Life:...
, a Scot
Scot
A Scot is a member of an ethnic group indigenous to Scotland, derived from the Latin name of Irish raiders, the Scoti.Scot may also refer to:People with the given name Scot:* Scot Brantley , American football linebacker...
tish surgeon. In 1829 he presented three cases at the Royal Society of London. Two cases were idiopathic and the third was due to a tumour of the parotid gland
Parotid gland
The paired parotid glands are the largest of the salivary glands. They are each found wrapped around the mandibular ramus, and secrete saliva through Stensen's ducts into the oral cavity, to facilitate mastication and swallowing and to begin the digestion of starches.-Location:The parotid glands...
.