BELL PALSY

BELL PALSY - Dylan C. Kwait, MD
BASICS
DESCRIPTION
• Peripheral lower motor neuron facial palsy, usually unilateral, which arises secondary to inflammation and subsequent swelling and compression of the 7th (facial) cranial nerve and the associated vasa nervorum.
• Synonym(s): Idiopathic facial paralysis
EPIDEMIOLOGY
• Accounts for 60-75% of all cases of unilateral facial paralysis (1)[A]
• Predominant age
- Median age of onset is 40 years, but affects all ages (2)[A].
• Predominant sex: Male = Female (2)[A]
Incidence
• Incidence in the US is 20-30 cases per 100,000 people per year (2)[A].
• Incidence is lowest in children 10 years of age; highest in people 70 years of age (2)[A].
• Incidence is higher among pregnant women (1)[A].
• Occurs with equal frequency on the left and right sides of the face (2)[A].
Prevalence
Affects 40,000 Americans every year (3)[A].
RISK FACTORS
• Pregnancy
• Diabetes mellitus
• Age >30
• Exposure to cold temperatures
• Upper respiratory infection (e.g., coryza, influenza)
Genetics
A genetic predisposition may be associated with Bell palsy, but it is unclear which factors are inherited.
ETIOLOGY
• Results from damage to the 7th (facial) cranial nerve
• Inflammation of the 7th nerve causes swelling and subsequent compression of both the nerve and the associated vasa nervorum
• May arise secondary to reactivation of latent herpes virus (herpes simplex virus type 1 and herpes zoster virus) in cranial nerve ganglia (1)[A].
• May arise secondary to ischemia from arteriosclerosis associated with diabetes mellitus (2)[A].
ASSOCIATED CONDITIONS
• Lyme disease
• Diabetes mellitus
• Hypertension
• Herpes simplex virus
• Herpes zoster virus
• Ramsay Hunt syndrome
• Sjogren syndrome
• Sarcoidosis
• Eclampsia
• Amyloidosis

DIAGNOSIS
SIGNS AND SYMPTOMS
• Weakness on affected side of face, often sudden in onset
• Pain in or behind the ear in 50% of cases (may precede the palsy in 25% of cases) (2)[A]
• Subjective numbness on the ipsilateral side of the face
• Alteration of taste on the ipsilateral anterior 2/3 of the tongue (chorda tympani branch of the facial nerve)
• Hyperacusis (nerve to the stapedius muscle)
• Decreased tear production
History
It is vital to elicit
• Time course of the illness (e.g., rapid vs. slow onset)
• Any predisposing factors (e.g., recent viral infection, trauma, new medications, hypertension, diabetes mellitus)
• Presence of hyperacusis or history of recurrent Bell palsy (both associated with poor prognosis)
• Any associated rash (suggestive of herpes zoster, Lyme disease, or sarcoid)
Physical Exam
• Neurologic examination to determine if the weakness is due to a problem in either the central or peripheral nervous systems
- Flaccid paralysis of muscles on the affected side, including the forehead
 Impaired ability to raise the ipsilateral eyebrow
 Impaired closure of the ipsilateral eye
 Bell phenomenon: Upward diversion of the eye with attempted closure of the lid
 Impaired ability to smile, grin or purse the lips
- Patients may complain of numbness, but on sensory testing, no deficit is present.
- Examine for involvement of other cranial nerves.
• HEENT
- Carefully examine head, neck, and oropharynx to exclude masses.
- Perform pneumatic otoscopic examination.
• Skin
- Examine for erythema migrans (Lyme disease) and vesicular rash (herpes zoster virus).
TESTS
• Electromyography
- Nerve conduction on affected and nonaffected sides can be compared to determine extent of nerve injury.
• Electroneurography
- Evoked potentials of affected and nonaffected sides can be compared.
• CSF analysis
- Not routinely indicated
- CSF protein is elevated in 1/3 of cases.
- CSF cells show mild elevation in 10% of cases with a mononuclear cell predominance.
Lab
• Lyme titer and IgM, IgG, and IgA for B. burgdorferi
• Salivary PCR for herpes simplex virus type 1 or herpes zoster virus (these tests are largely reserved for research purposes) (1)[A]
• IgM, IgG, and IgA titers for varicella zoster virus, cytomegalovirus, rubella, hepatitis A, hepatitis B, and hepatitis C
• ESR
• Blood glucose level
• CBC
• RPR test
• HIV test
Imaging
• Facial radiographs
- Rule out fractures
• CT
- Rule out fractures
- Rule out stroke
• Brain MRI
- Not routinely indicated
- Rule out central pontine, temporal bone, and parotid neoplasms (2)[A]
Diagnostic Procedures/Surgery
Invasive diagnostic procedures are not indicated, because biopsy could further damage the 7th nerve (4)[A].
Pathological Findings
• Dilatation of the vasa nervorum
• Edema of the facial nerve with infiltration of mononuclear cells and possible atrophy
DIFFERENTIAL DIAGNOSIS
• Infectious
- Lyme disease
- Herpes zoster (Ramsay-Hunt syndrome)
- Acute or chronic otitis media
- Malignant otitis externa
- Osteomyelitis of the skull base
- Infectious mononucleosis
- Leprosy
• Trauma injury
- Temporal bone fracture
- Mandibular bone fracture
• Neoplastic (should be considered in cases where onset of palsy is slow and progressive and accompanied by additional cranial nerve deficits and/or headache) (1)[A]
- Tumors of the parotid gland
- Cholesteatoma
- Skull-base tumor
- Carcinomatous meningitis
- Leukemic meningitis
• Cerebrovascular
- Brainstem stroke involving antero-inferior cerebellar artery
- Aneurysm involving carotid, vertebral or basilar arteries
• Other
- Multiple sclerosis
- Myasthenia gravis (should be considered in cases of recurrent or bilateral facial palsy) (2)[A]
- Guillain-Barre syndrome (may also present with bilateral facial palsy) (2)[A]
- Sjogren syndrome
- Sarcoidosis
- Amyloidosis
- Melkersson-Rosenthal syndrome
- Polyneuritis
TREATMENT
GENERAL MEASURES
• Artificial tears should be used to lubricate the cornea.
• The ipsilateral eye should be patched and taped shut at night to avoid drying and infection.
Diet
No restrictions
Activity
No restrictions
MEDICATION (DRUGS)
No evidence suggests that pharmacologic intervention (with anti-inflammatory and/or antiviral agents) or decompression surgery is any more beneficial than watchful waiting in terms of treatment or prevention of long-term effects. (4)[A]
ALERT
Pregnancy Considerations
Steroids should be used cautiously in pregnancy; consult with an obstetrician.
First Line
• Corticosteroids
- Prednisone (5)[B]: Total from 410 mg over 10 days to 760 mg PO over 16 days, tapering dose (adults only)
- Treatment should begin immediately after onset, and should not be instituted if symptoms have been present for >7 days.
- May reduce edema around the 7th cranial nerve; small benefit in adult patients, but use remains controversial.
• Antivirals
- Acyclovir (5)[B]: 400 mg PO 5 times per day for 10 days (adults only)
- Should be instituted within 72 hours, but may be started up to 7 days after onset of symptoms.
- Combination acyclovir and prednisone therapy may improve recovery rates when compared with prednisone alone. (5)[B]
• Contraindications
- Documented hypersensitivity
- Pre-existing infections including tuberculosis and systemic mycosis
• Precautions: Use with discretion in pregnancy, peptic ulcer disease, and diabetes.
• Significant possible interactions: Measles-mumps-rubella, oral polio virus vaccine, and other live vaccines
SURGERY
• Surgical treatment of Bell palsy remains controversial and is reserved for intractable cases (1)[A].
• The 7th cranial nerve is surgically decompressed at the entrance to the meatal foramen where the labyrinthine segment and geniculate ganglion reside. (2)[A]
• Decompression surgery should not be performed >14 days after the onset of paralysis because severe degeneration of the facial nerve is likely irreversible after 2-3 weeks. (2)[A]
FOLLOW-UP
DISPOSITION
Issues for Referral
Patients may need to be referred to an ear, nose, and throat specialist or a neurologist.
PROGNOSIS
• Most achieve complete spontaneous recovery within 2 weeks (3)[A].
• 85% of untreated patients will experience the 1st signs of recovery within 3 weeks of onset. (5)[C].
• Over 80% recover within 3 months (3)[A].
• 16% are left with a partial palsy, motor synkinesis, and autonomic synkinesis (1)[A].
• 5% experience severe sequelae, and a small number of patients experience permanent facial weakness and dysfunction (1)[A].
• Poor prognostic factors include
- Age >60 years
- Complete facial weakness
- Hypertension
- Ramsay-Hunt syndrome
- Absence of recovery at 3 weeks
COMPLICATIONS
• Corneal abrasion or ulceration
• Steroid-induced psychological disturbances; avascular necrosis of the hips, knees, and/or shoulders
• Steroid use can unmask subclinical infection (e.g., tuberculosis).
PATIENT MONITORING
• Patients should start treatment immediately and be followed for 12 months.
• Patients who do not recover complete facial nerve function should be referred to an ophthalmologist for tarsorrhaphy.
REFERENCES
1. Holland NJ, Weiner GM. Recent developments in Bell's palsy. Br Med J. 2004;329:553-557.
2. Gilden DH. Bell's palsy. N Engl J Med. 2004;351:1323-1331.
3. Holten K. How should we manage Bell's palsy? J Fam Pract. 2004;53(10):797-798.
4. Atkin PA. Diagnosis and the management of Bell's palsy. Practitioner. 2003;247(1642):36.
5. Peitersen E. The natural history of Bell's palsy. Am J Otol. 1982;4(2):107-111.
ADDITIONAL READING
Piercy J. Bell's palsy. Br Med J. 2005;330:1374.
MISCELLANEOUS
See also: Herpes simplex virus; Herpes zoster virus; Ramsay-Hunt syndrome; Sjogren syndrome; Sarcoidosis; Amyloidosis; Lyme disease; Diabetes mellitus; Melkersson-Rosenthal syndrome