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Bell Palsy

Basics

  • Acute, unilateral peripheral (lower motor neuron) facial nerve (CN VII) palsy
  • Usually idiopathic with edema and compression of nerve
  • Affects voluntary facial muscles on affected side
  • Incidence: up to 53 per 100,000 annually worldwide
  • Most common ages: 15-45 years
  • Equal left/right side involvement

Etiology and Pathophysiology

  • Inflammation causes perineurium edema → nerve and vasa nervorum compression
  • Reactivation of latent herpesviruses (HSV-1, VZV) implicated

Risk Factors

  • Pregnancy (especially with chronic hypertension, obesity, severe preeclampsia)
  • Immunosuppression
  • Diabetes mellitus
  • Upper respiratory infections (e.g., influenza A)
  • Chronic hypertension
  • Obesity
  • Extremes of temperature exposure

Diagnosis

History

  • Rapid onset (24-48 hours) of unilateral facial weakness
  • Inability to close eyelid, drooling from mouth
  • Progresses up to 3 weeks, with possible recovery over months
  • Symptoms may include mastoid/postauricular pain, hyperacusis, taste alteration, decreased lacrimation/salivation
  • Assess travel/area for Lyme disease, rashes (zoster)

Physical Exam

  • Flaccid paralysis of all muscles on affected side including forehead (distinguishes from stroke)
  • Bell phenomenon (eye moves upward when attempting closure)
  • Assess for sensory deficits (usually none)
  • Rule out other cranial nerve involvement
  • Skin exam: erythema migrans (Lyme), vesicular rash (zoster)

House-Brackmann Scale for severity

Grade Description
I Normal function
II Slight weakness, complete eyelid closure
III Moderate weakness, synkinesis noticeable
IV Disfiguring weakness, incomplete eye closure
V Severe paralysis

Differential Diagnosis

  • Infectious: Ramsay Hunt syndrome, Lyme disease, TB, HIV
  • Inflammatory: sarcoidosis, vasculitis, autoimmune
  • Neoplastic: tumors (schwannoma, parotid, CPA)
  • Cerebrovascular: stroke, aneurysm
  • Trauma

Diagnostic Tests & Interpretation

  • Clinical diagnosis; routine labs/imaging not needed in typical cases
  • Consider MRI, CT if atypical presentation, progressive symptoms, or >2 months duration
  • Blood tests: CBC, ESR/CRP, Lyme serology, RPR, HIV, VZV titers as indicated
  • Electrodiagnostic studies may guide prognosis
  • Parotid biopsy if no recovery and negative imaging at 7 months

Treatment

General Measures

  • Frequent artificial tears and eye lubrication
  • Tape or patch eye at night to prevent drying and infection

Medications

  • Corticosteroids improve recovery if started within 72 hours (NNT=10)
  • Recommended regimen:
  • Prednisolone 50 mg PO daily × 10 days, or
  • Prednisone 60 mg daily × 5 days, taper by 10 mg/day over next 5 days
  • Use cautiously with diabetes, peptic ulcer
  • Antivirals alone no proven benefit; consider adding valacyclovir/acyclovir if used with steroids
  • Pregnancy: cautious steroid use; antivirals category B

Issues for Referral

  • Persistent eyelid closure weakness → ophthalmology
  • No improvement/progression → ENT, neuroimaging
  • Bilateral, recurrent, prolonged symptoms → neurology
  • Children <2 years or trauma-associated → neurology/neurosurgery

Additional Therapies

  • Botulinum toxin for synkinesis or facial spasms post incomplete recovery
  • Physical therapy for severe or persistent paralysis (House-Brackmann V/VI)
  • Surgical decompression not recommended after 14 days of onset

Ongoing Care

  • Initiate steroids promptly
  • Monitor for recovery; refer if incomplete after 3-4 months
  • Protect eye integrity and vision

Patient Education

  • Most patients recover fully within weeks to months
  • Eye care to prevent corneal injury is essential
  • Recurrence possible in 7%
  • Distinguish from stroke by forehead involvement

Prognosis

  • 80% recover fully within 3 months
  • 85% show signs of recovery within 3 weeks untreated
  • Up to 30% have incomplete recovery
  • 5% severe sequelae, including permanent weakness
  • Poor prognosis factors: age >60, diabetes, complete palsy, recurrence

Complications

  • Corneal abrasions/ulcers
  • Steroid side effects: hyperglycemia, psychological changes, avascular necrosis
  • Facial synkinesis or blepharospasm from aberrant nerve regeneration