Bell's Palsy

See Also

Definitions

Bell's Palsy (Facial Nerve Palsy)
1. Idiopathic, acute Facial Nerve Paralysis

Background
History

Named for Sir Charles Bell (1774-1842) who first described the syndrome

Epidemiology

Incidence: 15-30 per 100,000 per year (45,000 per year in U.S.)
No gender predominance
Ages most commonly affected 15 to 45 years old (peaks at age 40-49 years)

Pathophysiology

Bell's Palsy is a Peripheral Nerve disorder (affecting the nerve after exiting its nucleii in the pons)
Only peripheral CN 7 lesions (Bell's Palsy) affect forehead motor activity
1. Both sides of the brain provide input to the forehead (redundant, dual innervation)
2. Any lesion affecting forehead motor activity must occur peripherally
3. Forehead motor activity (e.g. full Eyelid closure) is preserved in CNS Lesions (stroke)
Caused by Facial Nerve edema, compression or inflammation
1. Typically at Geniculate Ganglion (risk of ischemia, demyelination) after exiting the internal acoustic meatus
2. Associated with Herpesvirus infection in 30% of cases
Images

Risk Factors

Diabetes Mellitus (comorbid in 10% of cases)
Pregnancy (associated with 3 fold increased risk)
Immunosuppression
Influenza A
Herpesvirus infection (comorbid in 30% of cases)

History
Red Flags suggestive of other Facial Nerve Paralysis Cause

Gradual onset over >2 weeks
1. Suggests mass lesion
2. Mass lesion may also cause a recurrent unilateral Bell's Palsy
Forehead not involved
1. Suggests Central Nervous System cause (supranuclear lesion)
2. Facial Nerve motor nucleus is divided
  1. Dorsal aspect (forehead innervation) and ventral aspect (lower facial innervation)
  2. Both sides of the brain provide input to the dorsal aspect (forehead)
    1. Hence lack of forehead involvement implies an Upper Motor Neuron Lesion
  3. Only one side of the brain provides input to the ventral aspect (lower face)
Bilateral involvement
1. Suggests autoimmune Polyneuropathy
2. Lyme Disease
Recent new medications (e.g. Influenza Vaccine)
Acute Unilateral Weakness in other distributions (suggests CNS Lesion)
1. Extraocular Movement deficits
2. Unilateral limb weakness
3. Bulbar weakness
Lyme Disease Risk Factors (Tick Bite, endemic Lyme Disease region during peak season)
1. Lyme Disease
Fever
1. Consider infectious cause such as Otitis Media
Rash
1. Vesicular rash (Herpes Zoster, Ramsay Hunt Syndrome)
2. Erythema Migrans (Lyme Disease)
Hearing Loss and Vestibular Symptoms or Ataxia
1. Acoustic Neuroma
Children (esp. children age <5 years)
1. Otitis Media
2. Trauma
3. Herpes Simplex Virus
4. Varicella Zoster Virus
5. Lyme Disease
6. Malignancy (esp. Leukemia, Lymphoma, Brain Tumor)
  1. Associated with a 0.7% risk in children age <5 years (contrast with 0.3% overall)
  2. Evaluate for Hepatosplenomegaly and Lymphadenopathy, and ensure close follow-up
7. References
  1. Claudius and Walsh (2022) EM:Rap 22(9): 8-9
  2. Walsh (2022) Am J Emerg Med 53:63-7 +PMID:34992025 [PubMed]

Exam

Head and neck
1. External Ear and ear canal (e.g. Otitis Externa, Herpes Zoster, Ramsay Hunt Syndrome)
2. Tympanic Membrane (e.g. Otitis Media)
3. Mouth and pharynx (e.g. Herpes Simplex Virus)
4. Parotid Gland
Neurologic Exam
1. Perform complete Neurologic Exam including gait
2. Perform extremity Motor Exam and Sensory Exam
3. Cranial Nerve Exam
4. Test Cranial Nerve 7 bilaterally on lower face and forehead (forehead MUST be involved in Bell's Palsy)
  1. Raise eyebrows, wrinkling forehead
  2. Close eyes tightly
  3. Frown
  4. Show teeth
  5. Pucker lips
Skin
1. Vesicular rash (Herpes Zoster, Ramsay Hunt Syndrome)
2. Erythema Migrans (Lyme Disease)

Symptoms

Idiopathic Facial Nerve Paralysis developing over 1 to 3 days
Associated symptoms or signs
1. Hypoesthesia or dysesthesia (80%)
  1. Glossopharyngeal Nerve dysfunction
  2. Trigeminal Nerve dysfunction
2. Facial or retroauricular pain (60%)
3. Dysgeusia (57%)
4. Hyperacusis (30%)
5. Vagal nerve motor weakness (20%)
6. Decreased Lacrimation (17%)
7. Trigeminal Nerve motor weakness (3%)
8. Synkinesis (e.g. mouth twitching while blinking, or winking while smiling)
References
1. Adour (1982) N Engl J Med 307: 348-51 [PubMed]

Signs
General

Preserved facial Sensation
1. However hypoesthesia or dysesthesia is common (see above)
Mouth and nasolabial changes
1. Loss of facial creases and flattening of nasolabial fold
2. Corner of mouth droops
Eye changes
1. No closure or decreased closure of upper Eyelid
2. Lower Eyelid sag
3. Decreased tear production
No furrow over forehead (forehead appears flattened)
1. Critical to recognize when the forehead and Eyelid are not involved
2. Lack of forehead and Eyelid involvement suggests an Upper Motor Neuron Lesion such as a CVA

Signs
Facial Nerve Grading (House-Brackman)

Grade 1: Normal Facial Nerve Function
Grade 2: Mild Facial Nerve Dysfunction
1. Gross
  1. Slight weakness on close examination
  2. Synkinesis slight
2. Rest: Normal symmetry and tone
3. Motor Exam
  1. Forehead: Moderate to good function
  2. Eyes: Complete closure with minimum effort
  3. Mouth: Slight asymmetry
Grade 3: Moderate Facial Nerve Dysfunction
1. Gross:
  1. Obvious difference between sides (not disfiguring)
  2. Synkinesis noticeable
2. Rest: Normal symmetry and tone
3. Motor Exam
  1. Forehead: slight to Moderate movement
  2. Eyes: Complete closure with effort
  3. Mouth: Slightly weak with maximal effort
Grade 4: Moderately Severe Facial Nerve Dysfunction
1. Gross
  1. Obvious weakness
  2. Disfiguring asymmetry
2. Rest: Normal symmetry and tone
3. Motor Exam
  1. Forehead: No motor function
  2. Eyes: Incomplete closure
  3. Mouth: Asymmetric with maximal effort
Grade 5: Severe Facial Nerve Dysfunction
1. Gross: Barely perceptible motion
2. Rest: Asymmetry
3. Motor Exam
  1. Forehead: No motor function
  2. Eyes: Incomplete closure
  3. Mouth: Slight movement
Grade 6: Total Facial Nerve Paralysis
References
1. House (1985) Otolaryngol Head Neck Surg 93:146-7 [PubMed]

Differential Diagnosis

See Facial Nerve Paralysis Causes

Labs

Labs are not indicated in isolated peripheral Facial Nerve Paralysis
Serum Glucose is not routinely recommended
1. Diabetes Mellitus does not cause Bell's Palsy, and is simply a predisposing factor
Lyme Antibody titer is not routinely recommended
1. Lyme peripheral facial palsy is almost always associated with other findings (e.g. Arthritis, facial swelling, rash)
2. Isolated Facial Nerve Palsy is not typically due to Lyme Disease
3. However, consider empiric therapy for Lyme Disease and lyme test with risk factors in endemic regions
  1. Bilateral Facial Nerve involvement (high risk, treat as Lyme Disease while testing)
  2. Known recent deer Tick Bite
  3. Erythema Migrans (diagnostic without Lyme Titer)
  4. Peak season in endemic Lyme Disease region
4. References
  1. Kuiper (1992) Arch Neurol 49(9): 940-3 [PubMed]

Imaging
MRI Head With and Without Contrast

Benefits
1. MRI Identifies central causes (Schwannoma, Hemangioma, meningioma and Cholesteatoma)
2. MRI offers prognostic information based on nerve contrast enhancement
Indications
1. Suspected central cause (see Red Flags above)
2. Persistent or progressive peripheral Facial Nerve Palsy lasting >2 months
3. Facial twitching or spasm
4. Recurrent Bell Palsy

Management
Corticosteroids and Antimicrobials

Approach
1. Start Corticosteroid within 72 hours of onset
2. Antiviral may be considered in moderate to severe cases (House-Brackman Grade 4 and above)
3. Consider Lyme Disease management if suggested by history or exam
  1. Doxycycline (preferred) 100 mg bid or Amoxicillin 500 mg tid for 14-21 days
High dose Corticosteroids: Prednisone or Prednisolone (primary intervention)
1. Adult
  1. Protocol 1: 60 to 80 mg orally daily for 7 days
  2. Protocol 2: 60 mg daily for 5 days, then taper off over 5 days
  3. Worse recover was associated with cummulative Prednisone dosing <450 mg
    1. de Almeida (2009) JAMA 302(9): 985-93 [PubMed]
2. Child: 2 mg/kg/day (up to adult dosing) for 7 days
3. NNT 10 for full recovery in Bell Palsy treated with early Corticosteroids (<72 hours from onset)
4. Salinas (2010) Cochrane Database Syst Rev (3):CD001942 +PMID:20238317 [PubMed]
Antiviral Agents (optional)
1. Mechanism
  1. Based on reactivated HSV hypothesis
2. Indications
  1. Findings consistent with Herpes Zoster, herpes simplex or Ramsay Hunt Syndrome (e.g. vesicular rash)
  2. Antiviral may be considered in moderate to severe cases (House-Brackman Grade 4 and above)
3. Efficacy of empiric Antiviral use (excluding cases of herpetic, vesicular rashes which should be treated)
  1. Original studies showed synergistic benefit with Antivirals in combination with Corticosteroids
    1. More recent studies show primary improvement with Corticosteroids
    2. Only marginal added benefit with Antivirals
  2. Reasonable to offer Antivirals in moderate to severe cases
    1. However patients should be counseled on low efficacy of Antivirals
4. Agents
  1. Acyclovir
    1. Adult: 400 mg five times per day for 7 days
    2. Child (>2 years): 80 mg/kg daily (max: 3200 mg/day) divided every 6 hours for 5 days
  2. Valacyclovir
    1. Age >12 years: 1 gram orally three times daily for 7 days
5. References
Other antimcrobial considerations
1. Consider empiric Doxycycline in Lyme Disease endemic regions (esp. bilateral, peak tick season, known Tick Bite)

Management
Loss of Blink Reflex

Rewetting the eye
1. Frequent use of preservative-free artificial tears (every 15 to 30 minutes)
2. Refresh PM ointment six times daily
Protective glasses with side pieces
1. Use in outdoors, drafty, dusty areas
2. Alternatively can use eye shield or cup
Avoid grinding, sanding, or sawing
At night:
1. Apply bland ointment (Refresh PM, Lacri-Lube)
2. Tape eye shut
Ophthalmology Consultation indicated for incomplete Eyelid closure persisting for weeks
1. Risk of Keratitis, Corneal Ulcers and permanent ocular injury from dry, unprotected eye

Management
Associated Conditions

Otitis Media or Mastoiditis Complications
1. IV Antibiotics
2. Otolaryngology Consultation for possible wide incision of Tympanic Membrane
Herpes Zoster Oticus (Ramsay Hunt Syndrome)
1. See Herpes Zoster for Antiviral Agents
2. May be associated with Tinnitus and Hearing Loss
3. High dose Corticosteroids (1 mg/kg/day)
  1. Avoid in Diabetes Mellitus, Peptic Ulcer, Glaucoma

Management
Referral Indications

Otitis Media complications
Mastoiditis complications
Signs of secondary cause
1. Intracranial lesion or nerve impingement
Incomplete Eyelid closure persisting for weeks
1. Risk of permanent ocular injury from drying
2. Referral to ophthalmology for management beyond artificial tears
Other procedure referrals NOT routinely recommended
1. Facial Nerve decompression surgery (may rarely be indicated)
2. Laser Therapy
3. Hyperbaric oxygen
4. Intratympanic Corticosteroid Injection
5. Stellate Ganglion block
6. Physical Therapy (no evidence of benefit in Bell's Palsy)
  1. May consider for >3 month of Grade 5-6 findings

Prognosis
Factors associated with poor prognosis

Worse Prognosis with time needed for recovery
1. No recovery by 3 weeks suggests worse prognosis (15% of cases)
2. Further recovery occurs over 3-5 months
Hyperacusis
Diabetes Mellitus
Hypertension
Pregnancy
Facial Nerve with severe degeneration by EMG
Decreased tearing
Age over 60 years
Ramsay Hunt Syndrome (Herpes Zoster Virus)
Severe pain
1. Aural pain
2. Anterior facial pain
3. Radicular pain

Complications

Corneal Ulceration or Keratitis (due to incomplete Eyelid closure)
Permanent Eyelid weakness
Permanent facial asymmetry (e.g. impaired smiling)
1. May be trigger social anxiety, depressed mood and other related complications
Synkinesis (up to 26% of patients at one year from onset)
1. Misdirected nerve regrowth leads to co-contraction of unrelated Muscles innervated by CN7
2. Example: Blinking make occur with smiling

Prognosis

Early full recovery (66 to 85%) within 3 weeks (higher rates after 8 weeks)
1. Children age <14 years and pregnant women have full recovery in 90% of cases
Prolonged recovery (15%) over 3-5 months (higher risk with bilateral or severe Bell's Palsy)
1. Slight residual deficit: 12%
2. Mild residual deficit: 13%
3. Severe residual deficit: 4%
  1. Facial weakness
  2. Contracture or spasm
Recurrence: 6.5 to 8% of cases (mean interval 10 years)
1. Higher risk of recurrence in Diabetes Mellitus
2. Complete recovery in 66% of recurrent cases

Course

Maximal weakness at 3-7 days after onset
Most cases (85%) improve within 3 weeks even without treatment
1. Additional improvement may require up to 5 months
2. Prolonged recovery duration required for nerve regeneration

References

Herbert et al in Herbert (2015) EM:Rap 15(11): 3-4
Zalvan (1999) Consultant 39(1):39-48
Zvonar and Welsh (2021) Crit Dec Emerg Med 35(2): 25
Albers (2014) Am Fam Physician 89(3): 209-12 [PubMed]
Dalrymple (2023) Am Fam Physician 107(4): 415-20 [PubMed]
Gilden (2004) N Engl J Med 351:1323-31 [PubMed]
Holland (2004) BMJ 329:553-7 [PubMed]
Tiemstra (2007) Am Fam Physician 76:997-1002 [PubMed]