How should I evaluate and treat an adult with acute unilateral lower‑motor‑neuron facial palsy (suspected Bell’s palsy)?

Evaluation and Management of Acute Unilateral Lower Motor Neuron Facial Palsy

Start oral corticosteroids (prednisolone 50 mg daily for 10 days OR prednisone 60 mg daily for 5 days followed by a 5-day taper) within 72 hours of symptom onset for all patients ≥16 years old, and implement immediate eye protection measures for those with incomplete eyelid closure. 1

Initial Clinical Assessment

Confirm true lower motor neuron involvement by testing forehead function:

• Inability to wrinkle the forehead or raise the eyebrow on the affected side confirms peripheral (LMN) facial nerve involvement and distinguishes Bell's palsy from central stroke, which spares the forehead 1, 2
• Perform a complete cranial nerve examination; any additional cranial nerve deficit excludes Bell's palsy and mandates urgent imaging for brainstem pathology 1, 2
• Document the severity using the House-Brackmann grading system (1=normal to 6=complete paralysis) to guide prognosis and follow-up 1, 2

Red flags requiring urgent MRI with contrast (not Bell's palsy):

• Forehead sparing (suggests stroke) 1, 2
• Other cranial nerve involvement 1, 2
• Bilateral facial weakness 1, 2
• Progressive weakness beyond 3 weeks 1
• Recurrent paralysis on the same side 1
• Isolated branch paralysis 1
• Associated neurological symptoms (limb weakness, sensory changes, diplopia, anomia, language disturbance) 3, 4

Diagnostic Testing: What NOT to Order

Do not obtain routine laboratory tests or imaging for typical Bell's palsy presentations – these delay treatment beyond the critical 72-hour window without improving outcomes 1, 2

• No routine labs (strong recommendation) 1
• No routine CT or MRI for classic presentations 1
• No electrodiagnostic testing for incomplete facial paralysis 1
• Consider electrodiagnostic testing only for complete paralysis, performed 3-14 days after onset 1

Treatment Protocol (Within 72 Hours of Onset)

Corticosteroid therapy (MANDATORY):

• Prednisolone 50 mg once daily for 10 days (no taper needed) 1
  • OR Prednisone 60 mg once daily for 5 days, then taper by 10 mg daily for 5 days (stop on day 11) 1
• Evidence: 83% recovery at 3 months with steroids vs 64% with placebo (NNT=6) 1
• At 9 months: 94% recovery with steroids vs 82% with placebo 1

Antiviral therapy (OPTIONAL adjunct only):

• Never prescribe antivirals alone – they are completely ineffective as monotherapy 1, 5
• May add valacyclovir 1 g three times daily for 7 days OR acyclovir 400 mg five times daily for 10 days in combination with steroids for severe cases 1, 5
• Modest benefit: 96.5% recovery with combination vs 89.7% with steroids alone (absolute benefit +6.8%) 1
• This is classified as an "option" rather than a recommendation due to small incremental gain 1

Eye Protection (CRITICAL for All Patients with Incomplete Eye Closure)

Implement immediately to prevent corneal damage:

• Lubricating ophthalmic drops every 1-2 hours while awake 1
• Ophthalmic ointment at bedtime for sustained moisture 1
• Eye taping or patching at night with proper technique instruction to avoid corneal abrasion 1
• Sunglasses outdoors to protect against wind and debris 1
• Moisture chambers (polyethylene covers) for severe cases 1

Urgent ophthalmology referral if:

• Complete inability to close the eye 1
• Signs of corneal exposure (redness, pain, foreign body sensation, discharge, vision changes) 1
• Persistent lagophthalmos beyond 3 months 1

Prognosis Based on Initial Severity

Incomplete paralysis (any visible facial movement):

• Up to 94% complete recovery 1, 2
• Better prognosis overall 1, 2

Complete paralysis:

• Approximately 70% complete recovery within 6 months 1
• Up to 50% risk of incomplete recovery 1, 2
• 30% may experience permanent facial weakness with contractures 1

Mandatory Follow-Up and Referral Triggers

Refer to facial nerve specialist if:

• Incomplete facial recovery at 3 months after symptom onset 1
• New or worsening neurologic findings at any point 1, 3
• Development of ocular symptoms at any point 1, 3

Typical recovery timeline:

• Most patients begin showing improvement within 2-3 weeks 1
• Complete recovery typically occurs within 3-4 months 1

Special Populations

Children:

• Better prognosis with higher spontaneous recovery rates (up to 90%) 5
• Corticosteroid benefit is less conclusive in pediatrics 1
• May consider steroids for severe cases with caregiver shared decision-making 1

Pregnant women:

• Treat with oral corticosteroids within 72 hours after individualized risk-benefit assessment 1
• Eye protection measures are safe and essential 1

Diabetic patients:

• Diabetes is NOT a contraindication to corticosteroids 1
• Monitor blood glucose every 2-4 hours during first few days of steroid therapy 1
• Proactively adjust diabetes medications; consider adding NPH insulin with morning steroid dose 1
• The therapeutic benefit outweighs temporary hyperglycemia risk 1

Common Pitfalls to Avoid

• Delaying treatment beyond 72 hours eliminates steroid effectiveness 1
• Prescribing antivirals alone is completely ineffective and delays proper treatment 1
• Using standard methylprednisolone dose packs provides only 105 mg prednisone-equivalent vs the required 540 mg, representing significant underdosing 1
• Ordering unnecessary labs or imaging delays treatment and offers no benefit 1
• Failing to test forehead function can miss central stroke 1, 2
• Inadequate eye protection can lead to permanent corneal damage 1
• Missing red flags (other cranial nerve involvement, forehead sparing, progressive weakness) that indicate alternative diagnoses requiring imaging 1, 3, 4