Topic Editor: Grant E. Fraser, M.D., FRACGP, FACRRM, ASTEM

Review Date: 10/2/2012

Definition

Bell's palsy or Idiopathic Facial Paralysis is an acute unilateral facial paresis due to peripheral facial nerve dysfunction. The severity and duration of facial weakness is variable.

Description

• Bell's palsy is a unilateral peripheral lower motor neuron facial palsy; acute in onset, with evolution over a period of three days to one week, resulting in weakness or paralysis of the ipsilateral (same side) eyelid and facial muscles. This condition can affect taste and/or result in increased sound sensitivity on the affected side
• There should be no other neurological deficits with this condition, and no evidence of upper motor neuron involvement
• Traditionally defined as idiopathic, some theorize that its cause is reactivation of herpes viruses in the cranial nerve ganglia
• Up to 30% of people with acute peripheral facial palsy have other identifiable causes, such as stroke, tumor, middle ear disease, or Lyme disease
• Severe pain is more consistent with Ramsay Hunt syndrome caused by herpes zoster infection, which has a worse prognosis than Bell's palsy
• Most cases recover spontaneously within 3 weeks, but up to 30% have residual deficits

Epidemiology

Incidence/prevalence

• Reported incidence is 20/100,000/year or about 1 in 60 lifetime risk

Age

• Most prevalent between ages 15-45 years

Gender

• Male = Female

Risk factors

• Peak incidence occurs in the 15-45 year age group
• African American or Hispanic ancestry
• Diabetes
• Family history of Bell's palsy
• Hypertension
• Pregnancy
• Upper respiratory infection

Etiology

• Although the etiology of Bell's palsy remains uncertain, some theorize that reactivated herpes viruses from the cranial nerve ganglia has a key role in its development. Other possible viral causes include Epstein-Barr virus [EBV] (infectious mononucleosis), varicella-zoster, cytomegalovirus and HIV
• Other theories include facial nerve inflammation at the geniculate ganglion, which could result in compression of the nerve, ischemia and/or demyelination
• It may be secondary to arteriosclerotic ischemia of the facial nerve in diabetics
• Bell's palsy can also be one of the manifestations of neuro-Lyme disease

History

• Bell's palsy usually takes 3-7 days from the onset of symptoms to maximal weakness
• A more insidious onset or progression over more than 2 weeks should prompt reconsideration of the diagnosis
• If left untreated, 85% have at least partial recovery within 3 weeks of onset
• Presence of risk factors such as African American or Hispanic ancestry, arid/cold climate, hypertension, diabetes, pregnancy and a positive family history
• Unilateral facial weakness, ranging from mild to complete paralysis
• Complaint of altered facial sensation, probably related to paralysis, but when tested facial sensation is preserved
• Dribbling of food and saliva from the affected side of the mouth
• Dry eye and eye irritation on the affected side due to lack of blinking and decreased tear production
• Posterior auricular pain on the affected side
• Alteration of taste to the ipsilateral anterior 2/3rds of the tongue
• Otalgia on the affected side
• Ocular pain on the affected side
• Epiphora (overflow of tears onto the face) on the affected side
• Blurred vision on the affected side

Physical findings on examination

• Bell's palsy presents with signs and symptoms of a lower motor neuron lesion affecting muscles of the lower and upper face (forehead). This contrasts with upper motor neuron (UMN) lesions, where there is sparing of the forehead. UMN lesions, due to crossover result in much less effect on the forehead muscles
• Synkinesis: Involuntary synchronous movement of a facial region concomitant with reflex or voluntary movement in another facial region
• Disappearance of facial creases and nasolabial fold with a drooping corner of the mouth (with consequent deviation of angle of mouth to the opposite side) and drooling
• Lack of muscular tone and absence of furrowing of the forehead on the affected side
• Bell's phenomenon: Upward rolling of the eyeball with attempted closure of the eye
• Hyperacusis (unusual sensitivity to sound) on the affected side
• Dysgeusia (decreased or distorted taste) on the ipsilateral, anterior 2/3rds of the tongue
• Decreased tear production (facial nerve carries parasympathetic fibers to the lacrimal gland)
• Erythema migrans (Lyme disease) or vesicular rash (herpes zoster or herpes simplex virus)
• Degree of paralysis can be described using the House-Brackmann scale where 1 is normal power and 6 is total paralysis:
• Grade I
• Normal symmetrical function
• Grade II
• Slight weakness, noticeable only on close inspection
• Complete eye closure with minimal effort
• Slight asymmetry of smile with maximal effort
• Synkinesis barely noticeable; contracture or spasm absent
• Grade III
• Obvious weakness, but not disfiguring
• May not be able to lift eyebrow
• Complete eye closure and strong but asymmetrical mouth movement
• Obvious, but not disfiguring synkinesis, mass movement or spasm
• Grade IV
• Obvious disfiguring weakness
• Inability to lift eyebrow
• Incomplete eye closure and asymmetry of the mouth with maximal effort
• Severe synkinesis, mass movement, spasm
• Grade V
• Facial motion barely perceptible
• Incomplete eye closure, slight movement to the corner of the mouth
• Synkinesis, contracture, and spasm usually absent
• Grade VI
• No movement, loss of tone, no synkinesis, contracture, or spasm

Blood test findings

Blood tests are generally of no value, except in certain cases of clinical suspicion for an underlying condition, or where other clinical findings are present. In such cases, limited focused testing can occasionally be indicated. As clinically indicated, a selection of the following tests may be appropriate:

• Blood glucose level or Hemoglobin A1c to detect undiagnosed diabetes
• CBC
• CSF analysis
• HIV test
• IgA, IgG, IgM titers for Varicella zoster, Cytomegalovirus, rubella, Hepatitis A, Hepatitis B, and hepatitis C
• Lyme titer (IgA, IgG, IgM for B. burgdorferi)
• RPR test for syphilis
• Salivary PCR for HSV1 or herpes zoster
• Thyroid function studies

Radiographic findings

• Radiologic testing is not routinely indicated in classic Bell's palsy; however, where there are other findings or concerns, some clinicians might order one or more of the following:
• Facial radiographs or CT to rule out fracture
• Head CT to evaluate for stroke, mass, hemorrhage, or skull fracture
• MRI brain to evaluate central pontine, temporal bone, and parotid neoplasms

Other diagnostic test findings

EEMG/CMAP/EMG are rarely indicated, but in selected cases can be useful.

• Evoked electromyography (EEMG): Reduced compound muscle action potential (CMAP), a common finding; however, severely decreased CMAP, a uncommon finding, suggests a severe lesion
• EMG: Fibrillations, reduced or absent voluntary motor unit potentials

Lower Motor Neuron

• Idiopathic
• Infective
• Cholesteatoma
• Herpes virus (type 1)
• Herpes zoster (Ramsay Hunt's syndrome)
• Lyme disease involving central nervous system
• Otitis media
• Neoplastic
• Parotid gland tumors
• Neurological
• Guillain-Barré syndrome
• Mononeuropathy (amyloidosis, diabetes mellitus, sarcoidosis, etc.)
• Sjögren's syndrome

• Cerebrovascular disease
• HIV
• Intracranial tumors, primary and secondary
• Multiple sclerosis
• Syphilis
• Vasculitides

General treatment items

• Most patients recover without treatment; 71% achieve complete recovery, 84% achieve near-normal function
• The goal of treatment in the acute phase focuses on strategies to speed recovery and prevent corneal complications
• Eye care includes eye patching and lacrilube eye ointment to protect the eye as poor lid closure, and decreased blinking and tear production results in corneal drying and risk of abrasion
• Systemic corticosteroids have demonstrated efficacy for Bell's palsy; whereas, antiviral agents have no added benefit. Antiviral agents are not recommended except when there are lesions consistent with herpes simplex or zoster
• The rationale for corticosteroids in Bell's palsy is an anti-inflammatory action on the facial nerve
• Decompression surgery remains controversial and is reserved for severe or intractable cases. One study demonstrated best results if the decompression occurred within 14 days of the onset of paralysis

Medications indicated with specific doses

• Artificial tears PRN daytime
• Lacrilube ointment: At least qid and prn
• Prednisone
• Adult Dosing
• Pediatric Dosing
• Prednisolone
• Adult Dosing
• Pediatric Dosing
• Antiviral agents: Indicated when patients show specific lesions of herpes simplex or herpes zoster
• Acyclovir
• Adult Dosing
• Pediatric Dosing
• Famciclovir
• Adult Dosing
• Pediatric Dosing
• Valacyclovir
• Adult Dosing
• Pediatric Dosing

Monitoring

• Early follow up within 1-2 weeks after the initial visit, then monthly for 2-3 months, then follow-up at 3 and 6 months
• Monitor pregnant women who develop Bell's palsy closely for development of hypertensive disorders of pregnancy

Complications

• Contracture and synkinesis
• Ectropion (sagging lower eyelid)
• Ocular damage, including corneal ulceration, due to lack of eye blinking and subsequent dry eyes

Prevention

• Secondary prevention: Avoid eye exposure to wind, dust, and trauma

Prognosis

• Most cases resolve entirely within a few weeks
• Persistent symptoms include:
• Decreased tearing
• Facial muscle/eyelid spasms
• Facial muscle weakness
• Persisting change in taste

Associated conditions

• Amyloidosis
• Diabetes mellitus
• Herpes simplex infection
• Herpes zoster infection
• Hypertension
• Lyme disease
• Pre-eclampsia
• Ramsay-Hunt syndrome
• Sarcoidosis
• Sjögren syndrome

Pregnancy/Pediatric affects on condition

• Bell's palsy incidence is higher in 3rd trimester. Some theorize this might be due to altered susceptibility to herpes simplex viral reactivation in late pregnancy
• Some relationship exists between Bell's palsy in pregnancy with increased risk of developing hypertensive disorders of pregnancy (e.g. pre-eclampsia, pregnancy induced hypertension)
• Prognosis is worse in pregnancy (as compared to Bell's palsy in non-pregnant patients)

Synonyms

• Idiopathic facial paralysis
• Facial palsy

ICD-9-CM

• 351.0 Bell's palsy

ICD-10-CM

• G51.0 Bell's Palsy

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