What is the recommended diagnostic work‑up and management for an adult with acute unilateral lower‑motor‑neuron facial paralysis suggestive of Bell’s palsy?

Diagnosis and Management of Bell's Palsy

Diagnosis

Bell's palsy is a clinical diagnosis of exclusion requiring rapid onset (<72 hours) of unilateral facial weakness involving the forehead, with no identifiable cause after thorough history and physical examination. 1, 2

Essential Diagnostic Features

• Acute onset within 72 hours of complete unilateral lower motor neuron facial weakness affecting the entire ipsilateral face, including the forehead 1, 2
• Forehead involvement is mandatory—this distinguishes Bell's palsy from stroke, which spares the forehead due to bilateral cortical innervation 2, 3
• Associated symptoms may include ipsilateral ear or facial pain, taste disturbance on the anterior two-thirds of the tongue, hyperacusis, and dry eye 1, 2

History and Physical Examination

• Document the exact timeline of symptom onset—progression beyond 72 hours or gradual onset over days to weeks suggests alternative diagnoses such as tumor or infection 2, 3
• Test all other cranial nerves systematically—any involvement of CN V, VI, VIII, IX, X, XI, or XII excludes Bell's palsy and mandates imaging for brainstem or skull base pathology 1, 3
• Assess facial movement by asking the patient to raise eyebrows, close eyes tightly, smile, and puff out cheeks 1, 2
• Use the House-Brackmann grading system (Grade 1 = normal to Grade 6 = total paralysis) to document severity 1, 2
• Evaluate eye closure carefully—incomplete closure requires immediate eye protection measures 1

Red Flags Requiring Imaging or Alternative Diagnosis

• Bilateral facial weakness—extremely rare in Bell's palsy; investigate for Lyme disease, sarcoidosis, or Guillain-Barré syndrome 2, 3
• Recurrent paralysis on the same side—requires workup for tumor, sarcoidosis, or diabetes 3
• Isolated branch paralysis—not consistent with Bell's palsy; suggests focal structural lesion 3
• Progressive weakness beyond 3 weeks—immediate reassessment required for alternative diagnosis 1
• Other neurologic findings (dizziness, dysphagia, diplopia, limb weakness)—suggests stroke or brainstem pathology 3

Diagnostic Testing

• Routine laboratory tests and imaging are NOT recommended for typical Bell's palsy presentations—they delay treatment without improving outcomes 1
• MRI with and without contrast is indicated only for atypical presentations: symptoms persisting >2–3 months, recurrent episodes, bilateral weakness, other cranial nerve involvement, or progressive worsening 1, 3
• Electrodiagnostic testing may be offered to patients with complete facial paralysis (performed 3–14 days post-onset), but is NOT recommended for incomplete paralysis 1

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Management

Prescribe oral corticosteroids within 72 hours of symptom onset for all patients ≥16 years old—this is the only proven effective treatment and significantly improves facial nerve recovery. 1

Corticosteroid Therapy (First-Line Treatment)

• Prednisolone 50 mg once daily for 10 days (no taper required) OR 1
• Prednisone 60 mg once daily for 5 days, followed by a 5-day taper 1
• Initiate within 72 hours of symptom onset—no benefit when started later 1
• Evidence shows 83% complete recovery at 3 months with prednisolone versus 63.6% with placebo (NNT = 6), and 94.4% recovery at 9 months versus 81.6% with placebo (NNT = 8) 1

Antiviral Therapy

• Antiviral monotherapy is never appropriate—acyclovir or valacyclovir alone provide no benefit and should never be prescribed 1
• Combination therapy (antiviral + corticosteroid) may be offered within 72 hours as an option, yielding a small incremental benefit: 96.5% complete recovery versus 89.7% with steroids alone (absolute benefit +6.8%) 1
• If offering combination therapy: valacyclovir 1000 mg three times daily for 7 days or acyclovir 400 mg five times daily for 10 days 1
• The large BELLS trial (n=496) found no statistically significant advantage of adding acyclovir: 71.2% recovery with acyclovir versus 75.7% without at 3 months 1

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

• Lubricating ophthalmic drops every 1–2 hours while awake 1
• Ophthalmic ointment at bedtime for sustained moisture retention 1
• Eye taping or patching at night with careful instruction on proper technique to avoid corneal abrasion 1
• Sunglasses outdoors to protect against wind and debris 1
• Moisture chambers using polyethylene covers for severe cases 1
• Urgent ophthalmology referral for severe impairment with complete inability to close the eye, or any signs of corneal exposure or damage 1

Follow-Up and Referral Triggers

• Mandatory reassessment or specialist referral at 3 months if facial recovery is incomplete 1
• Immediate referral for new or worsening neurologic findings at any point 1
• Immediate ophthalmology referral for development of ocular symptoms (eye pain, vision changes, redness, discharge) at any point 1
• Most patients begin showing recovery within 2–3 weeks, with complete recovery typically occurring within 3–4 months 1

Interventions NOT Recommended

• Physical therapy—no proven benefit over spontaneous recovery 1
• Acupuncture—poor-quality trials with indeterminate benefit-harm ratio 1
• Surgical decompression—not advised except in rare, highly selected cases at specialized centers 1

Special Populations

• Children: Better prognosis with higher spontaneous recovery rates; corticosteroid benefit is inconclusive, so treatment decisions should involve substantial caregiver participation 1
• Pregnancy: Treat with oral corticosteroids within 72 hours after individualized risk-benefit assessment; eye protection is essential and safe 1
• Diabetes: Corticosteroids are not contraindicated; monitor blood glucose every 2–4 hours during the first few days and adjust diabetes medications proactively 1

Prognosis

• Patients with incomplete paralysis have excellent prognosis with recovery rates up to 94% 1
• Patients with complete paralysis have approximately 70% complete recovery within 6 months 1
• 30% may experience permanent facial weakness with muscle contractures, requiring long-term management including possible reconstructive surgery 1

Common Pitfalls to Avoid

• Delaying corticosteroid treatment beyond 72 hours eliminates therapeutic benefit 1
• Prescribing antiviral monotherapy—this is ineffective and delays appropriate treatment 1
• Failing to assess forehead function—this leads to misdiagnosis of stroke as Bell's palsy 2, 3
• Missing other cranial nerve involvement—this excludes Bell's palsy and indicates serious pathology requiring urgent imaging 1, 3
• Inadequate eye protection—this can lead to permanent corneal damage 1
• Failing to refer at 3 months for incomplete recovery—this delays access to reconstructive options and psychological support 1