AUTHOR AND EDITOR INFORMATION

Section 1 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Acknowledgments
• Multimedia
• References

INTRODUCTION

Section 2 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Acknowledgments
• Multimedia
• References

Background

Bell's palsy is a unilateral, peripheral facial paresis or paralysis that has an abrupt onset and no detectable cause. Bell palsy is one of the most common neurologic disorders affecting the cranial nerves, and it is certainly the most common cause of facial paralysis worldwide. Although this syndrome was first described in 1821, by the Scottish anatomist and surgeon Sir Charles Bell, much controversy still surrounds its etiology and management.

The onset of Bell's palsy can be frightening for patients, who often fear they have had a stroke or have a tumor and that the distortion of their facial appearance will be permanent. Consequently, patients with Bell's palsy frequently present to the ED before seeing any other health care professional.

It is imperative to keep in mind that Bell's palsy is a diagnosis of exclusion. Other disease states or conditions that present as facial palsies are often misdiagnosed as idiopathic. In addition to excluding other causes of facial paralysis, the role of the ED clinician consists of the following:

• Initiate appropriate treatment.
• Protect the eye.
• Arrange appropriate medical follow-up care.

For related CME/CE activities, see CME/CE - Evidence-Based Management of Bell's Palsy: A Best Evidence Review and CME - Prednisolone Significantly Improves Recovery in Bell's Palsy.

A variety of nonpharmacologic measures have been used to treat Bell's palsy, including physical therapy (eg, facial exercises¹, neuromuscular retraining²) and acupuncture.³ No adverse effects of these treatments have been reported. Reviews suggest that physical therapy may result in faster recovery and reduced sequelae, but further randomized controlled trials are needed to confirm any benefit.

Pathophysiology

The precise pathophysiology of Bell's palsy remains an area of continuing debate. A popular theory proposes that inflammation and swelling of the facial nerve results in compression of the nerve within the temporal bone.

The facial nerve courses through a portion of the temporal bone commonly referred to as the facial canal. The first portion of the facial canal, the labyrinthine segment, is narrowest; the meatal foramen in this segment has a diameter of only about 0.66 mm. Given the tight confines of the facial canal, it seems logical that inflammatory, demyelinating, ischemic, or compressive processes may impair neural conduction at this site.

Anatomy

The facial nerve (seventh cranial nerve) has 2 components. The larger portion comprises efferent fibers that stimulate the muscles of facial expression. The smaller afferent portion contains taste fibers to the anterior two thirds of the tongue, secretomotor fibers to the lacrimal and salivary glands, and some pain fibers.

Pathway

The path of the facial nerve is complex; this may be the reason the nerve is vulnerable to injury. Two portions of the facial nerve leave the brain at the cerebellopontine angle, traverse the posterior cranial fossa, dive into the internal acoustic meatus, pass through the facial canal in the temporal bone, then angle sharply backwards, where they pass behind the middle ear and exit the cranium at the stylomastoid foramen. From here, the facial nerve bisects the parotid gland, and then terminal branches extend from the parotid plexus to innervate the muscles of facial expression.

Frequency

United States

The incidence of Bell's palsy in the United States is approximately 23 cases per 100,000 persons. The condition affects approximately 1 person in 65 in a lifetime. However, the incidence is 29% higher in persons with diabetes mellitus than in those without diabetes.

International

The incidence is similar to that in the United States, with the highest incidence reported in Japan.⁴

Mortality/Morbidity

Bell's palsy can cause aesthetic, functional, and psychological disturbances in patients who have residual nerve dysfunction during their recovery phase or in patients with incomplete healing.

• Partial paralysis
• Motor synkinesis (involuntary movement accompanying a voluntary movement)
• Autonomic synkinesis (involuntary lacrimation after a voluntary muscle movement)

Race

Incidence of Bell palsy appears to be slightly higher in persons of Japanese descent.

Sex

No difference exists in sex distribution in patients with Bell's palsy. In women, the overall incidence of Bell's palsy during pregnancy is comparable to that of all women of childbearing age; however, the incidence is high in the third trimester and correspondingly low during early pregnancy.⁵

Age

The incidence of Bell's palsy increases between the ages of 10 and 30 years. Bell's palsy is least common in persons younger than 10 years and most common in those older than 70 years.⁶

CLINICAL

Section 3 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Acknowledgments
• Multimedia
• References

History

Most patients presenting to the ED suspect they have suffered a stroke or have an intracranial tumor. The most common complaint is of weakness on one side of the face.

• Postauricular pain: Almost 50% of patients experience pain in the mastoid region. The pain frequently occurs simultaneously with the paresis, but precedes the paresis by 2-3 days in about 25% of patients.
• Tear flow: Two thirds of patients complain about tear flow. This is due to the reduced function of the orbicularis oculi in transporting the tears. Fewer tears arrive at the lacrimal sac and overflow occurs. The production of tears is not accelerated.
• Altered taste: While only one third of patients complain about taste disorders, four fifths of patients show a reduced sense of taste. Patients may fail to note reduced taste because of normal sensation in the uninvolved side of the tongue.
• Dry eyes
• Hyperacusis: Impaired tolerance to typical levels of noise as a result of paralysis of the stapedius muscle.

Physical

Findings of facial paralysis are easily recognizable on physical examination. A careful, complete examination excludes other possible causes of facial paralysis. Strongly consider other etiologies if all branches of the facial nerve are not affected.

• Weakness and/or paralysis from involvement of the facial nerve affects the entire face (upper and lower) on the affected side. Focus attention on the voluntary movement of the upper part of the face on the affected side: in supranuclear lesions such as a cortical stroke (upper motor neuron; above the facial nucleus in the pons), the upper third of the face is spared while the lower two thirds are paralyzed. The orbicularis, frontalis, and corrugator muscles are innervated bilaterally, which explains the pattern of facial paralysis in these cases.
• Eye closure on the affected side may be partially or completely impaired. On attempting to close the eye, the patient may demonstrate the Bell phenomenon: the eye on the affected side rolls upward and inward.
• All the other cranial nerves should be tested; results should be normal.
• Tympanic membranes should be normal; the presence of inflammation, vesicles, or other signs of infection raises the possibility of complicated otitis media.

Causes

The etiology of Bell's palsy remains unclear, although vascular, infectious, genetic, and immunologic causes have all been proposed. Patients with other diseases or conditions (eg, Lyme disease) sometimes develop a peripheral facial nerve palsy, but these are not classified as Bell's palsy (see Differentials).

• Viral infections: Clinical and epidemiologic data lend credence to an infectious origin, with inflammation and/or a related autoimmune response resulting in local demyelination of the facial nerve. Pathogens leading the list include herpes simplex virus type 1 (HSV-1); herpes simplex virus type 2 (HSV-2); human herpesvirus (HHV); varicella-zoster virus (VZV);  influenza B; adenovirus; coxsackievirus; Ebstein-Barr virus; hepatitis A, B, and C viruses; cytomegalovirus (CMV); and rubella virus.
• Mycoplasma infection: Bell's palsy may be a complication of M pneumoniae infection, sometimes in the absence of respiratory symptoms.
• Genetics: A family history of Bell's palsy has been reported in approximately 4% of cases. Inheritance in such cases may be autosomal dominant with low penetration. Which predisposing factors are inherited is unclear.

DIFFERENTIALS

Section 4 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Acknowledgments
• Multimedia
• References

Other Problems to be Considered

Herpes zoster
Ramsey-Hunt syndrome
Zoster sine herpete
Pregnancy (especially third trimester)
Polyneuritis
Acute otitis
Chronic otitis
Temporal bone fracture
Infectious mononucleosis
Parotid tumors
Sarcoidosis
Cholesteatoma of the middle ear
Aneurysm of vertebral, basilar artery, or carotid arteries
Carcinomatous meningitis
Facial trauma (blunt, penetrating, iatrogenic)
Leukemic meningitis
Leprosy
Melkersson-Rosenthal syndrome
Middle ear surgery
Osteomyelitis of the skull base
Skull base tumor

WORKUP

Section 5 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Acknowledgments
• Multimedia
• References

Lab Studies

• No specific laboratory tests exist to confirm the diagnosis of Bell's palsy. Clinical setting determines tests that may be of value. Results of the following laboratory tests may confirm or suggest other potential causes in the differential diagnosis:
• • Complete blood count
  • Erythrocyte sedimentation rate
  • Thyroid function studies
  • Lyme titer
  • Serum glucose level
  • Rapid plasma reagin (RPR) or Venereal Disease Research Laboratory (VDRL) test
  • Human immunodeficiency virus (HIV) antibodies
  • Cerebral spinal fluid analysis
  • Immunoglobulin M (IgM), immunoglobulin G (IgG), and immunoglobulin A (IgA) titers for CMV; rubella; HSV; hepatitis A virus; hepatitis B virus; hepatitis C virus; VZV; M pneumoniae; and Borrelia burgdorferi

Imaging Studies

• Bell's palsy remains a clinical diagnosis. Imaging studies are not indicated in the ED. Excluding other causes of facial palsy may require one of the following imaging studies, depending on clinical setting.
• • Facial CT scan or plain radiographs: Perform to rule out fractures or bony metastasis.
  • CT scan: Perform when the differential diagnosis includes stroke or CNS involvement from acquired immunodeficiency syndrome (AIDS).
  • MRI: Perform in patients with a suspected neoplasm of the temporal bone, brain, parotid gland, or other structure, or to evaluate for multiple sclerosis. MRI can visualize the course of the facial nerve through the intratemporal and extratemporal regions from the brain to the facial muscles and glands. MRI also may be considered in lieu of CT scan.

Other Tests

• Electrodiagnosis of the facial nerve: These studies assess the function of the facial nerve. These tests are rarely performed on an emergent basis.
• • Electromyography (EMG) and nerve conduction velocities produce a graphic readout of the electrical currents displayed by stimulating the facial nerve and recording the excitability of the facial muscles it supplies. Comparison to the contralateral side helps determine the extent of nerve injury and has prognostic implications. This is not part of the acute workup.
  • The nerve excitability test determines the threshold of the electrical stimulus needed to produce visible muscle twitching.
  • Electroneurography (ENoG) compares evoked potentials on the paretic side versus the healthy side.

TREATMENT

Section 6 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Acknowledgments
• Multimedia
• References

Emergency Department Care

The primary treatment of patients with Bell's palsy in the ED is pharmacologic management. The remainder of care focuses on reassurance, eye care instructions, and appropriate follow-up care.

• Steroids
• • Treatment of Bell's palsy with steroids remains controversial. Numerous small studies have shown conflicting results using steroids in treating Bell's palsy. However, a recent randomized controlled trial showed significant improvement in outcomes when prednisolone was started within 72 hours of symptom onset.
  • Experts suggest using steroids as a means to optimize outcomes. Once the decision to use steroids is made, the consensus is to start immediately.
• Antiviral agents: Although there is insufficient research evaluating the efficacy of antiviral medicines in Bell's palsy, most experts believe that the syndrome may result from viral infection. Therefore, antiviral agents seem a logical choice for pharmacologic management and are commonly recommended.
• Eye care: Impaired eye closure and abnormal tear flow are common with Bell's palsy. These leave the eyes at risk for corneal drying and foreign body exposure. Manage with tear substitutes, lubricants, and eye protection.
• • Artificial tears: Use these during waking hours to replace diminished or absent lacrimation.
  • Lubricants are used during sleep. They may be used during waking hours if artificial tears cannot provide adequate protection. One disadvantage is blurred vision during waking hours.
  • Eyeglasses or shields protect the eye from injury and reduce drying by decreasing direct contact of air currents with the exposed cornea. Eye patches, however, are ineffective because unopposed third nerve function will result in corneal exposure despite best efforts to approximate eyelid margins.

Consultations

The patient's primary care provider or consultant should provide close follow-up care. Documentation should chart the progress of the patient's recovery.

Opinions widely vary on referral to a specialist. Some specific referral indications are listed below:

• Neurologist: Consult a neurologist when other neurologic signs are identified on physical examination and for an atypical presentation of Bell's palsy.
• Ophthalmologist: Consult an ophthalmologist for any unexplained ocular pain or abnormal findings on physical examination of the eyes.
• Otolaryngologist: Consult an otolaryngologist for patients with persistent paralysis, prolonged weakness of the facial muscles, or recurrent weakness.
• Surgeon: Surgery to decompress the facial nerve is occasionally recommended for patients with Bell's palsy. Patients with a poor prognosis, identified by facial nerve testing or persistent paralysis, appear to benefit the most from surgical intervention.

MEDICATION

Section 7 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Acknowledgments
• Multimedia
• References

Watchful waiting is an option for management of Bell's palsy, because most cases resolve without medication. However, some individuals with Bell's palsy never fully recover. For both medications listed below, there are clinical trials that support their efficacy and trials that dispute it.

Drug Category: Corticosteroids

These agents have anti-inflammatory properties and cause profound and varied metabolic effects. They modify the body's immune response to diverse stimuli.

Drug Category: Antivirals

Herpes simplex infections may be a common cause of Bell's palsy. Acyclovir is the antiviral agent most often used, but others may also be appropriate.

Valacyclovir is a prodrug of acyclovir and produces blood levels of acyclovir that are 3-5 times higher than those produced by oral acyclovir.

FOLLOW-UP

Section 8 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Acknowledgments
• Multimedia
• References

In/Out Patient Meds

• Consider prednisone at an initial dose of 1 mg/kg/d up to 60 mg.
• • Prednisone is a potent drug with a potential for side effects. Older studies are mixed in showing efficacy. A recent double-blinded, randomized controlled trial showed benefit if treatment was started within 72 hours.
  • The best prednisone regimen for Bell's palsy is a short burst (up to 10 d), but steroid taper may also be used.
• Consider using antivirals within 72 hours.
• • Administer acyclovir (Zovirax) 800 mg PO 5 times/d for 10 d; 20 mg/kg in patients younger than 2 years. Recent evidence supports HSV as a major cause of Bell's palsy. However, evidence of efficacy with acyclovir has been mixed.
  • Valacyclovir (Valtrex), 500 mg PO twice a day for 5 days, may be used instead of acyclovir. Although more expensive, this may lead to better compliance. If VZV is the cause, higher doses may be needed (1000 mg PO tid). However, because of increased cost and increased risk of side effects, valacyclovir cannot be routinely recommended at this time.

Complications

• Most patients with Bell's palsy recover without any cosmetically obvious deformities; however, approximately 5% are left with an unacceptably high degree of sequelae.
• Incomplete motor regeneration
• • The largest portion of the facial nerve comprises efferent fibers that stimulate muscles of facial expression. Suboptimal regeneration of this portion results in paresis of all or some of these facial muscles.
  • This manifests as (1) oral incompetence, (2) epiphora (excessive tearing), and (3) nasal obstruction.
• Incomplete sensory regeneration
• • Dysgeusia (impairment of taste) may result.
  • Ageusia (loss of taste) may result.
  • Dysesthesia (impairment of sensation or disagreeable sensation to normal stimuli) may result.
• Aberrant reinnervation of the facial nerve
• • During regeneration and repair of the facial nerve, some neural fibers may take an unusual course and connect to neighboring fibers. This aberrant reconnection produces unusual neurologic pathways.
  • When voluntary movements are initiated, they are accompanied by involuntary movements (eg, the movement of a closed eye following that of the uncovered one). These involuntary movements accompanying voluntary movement are termed synkinesis.

Prognosis

• The natural course of Bell's palsy varies from early complete recovery to substantial nerve injury with permanent sequelae. Prognostically, patients fall into 3 groups:
• • Group 1 - Complete recovery of facial motor function without sequelae
  • Group 2 - Incomplete recovery of facial motor function, but no cosmetic defects are apparent to the untrained eye
  • Group 3 - Permanent neurologic sequelae that are cosmetically and clinically apparent
• Patients who experience incomplete facial paralysis during the acute phase have an excellent prognosis for full recovery. Patients demonstrating complete paralysis are at higher risk for severe sequelae.
• Of patients with Bell's palsy, 85% achieve complete recovery, 10% have some persistent asymmetry of facial muscles, and 5% experience severe sequelae.
• The prognosis in pregnant women with Bell's palsy is significantly worse than it is in nonpregnant women with Bell's palsy.

Patient Education

• Eye care
• • Protect the eye from foreign objects and sunlight.
  • Keep the eye well lubricated.
  • Educate the patient to report new ocular findings such as pain, discharge, or visual changes.
• For excellent patient education resources, visit eMedicine's Brain and Nervous System Center. Also, see eMedicine's patient education article Bell Palsy.

ACKNOWLEDGMENTS

Section 9 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Acknowledgments
• Multimedia
• References

The authors and editors of eMedicine gratefully acknowledge the contributions of previous author, Michael Lambert, MD, to the development and writing of this article.

MULTIMEDIA

Section 10 of 11  

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Acknowledgments
• Multimedia
• References

Media file 1:  The facial nerve.
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Media type:  Image

REFERENCES

Section 11 of 11

• Authors and Editors
• Introduction
• Clinical
• Differentials
• Workup
• Treatment
• Medication
• Follow-up
• Acknowledgments
• Multimedia
• References

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Article Last Updated: Oct 7, 2008