How should I evaluate and manage a patient who presents with an acute lower motor neuron facial palsy?

Evaluation and Management of Acute Lower Motor Neuron Facial Palsy

Immediate Clinical Assessment

Begin oral corticosteroids within 72 hours of symptom onset for all patients ≥16 years with acute LMN facial palsy—this is the single most important intervention to improve recovery. 1

History: Critical Red Flags to Exclude

• Onset timeline: True Bell's palsy develops within 72 hours; progressive weakness beyond 3 weeks mandates imaging for tumor or other pathology 1, 2
• Associated neurologic symptoms: Any dizziness, dysphagia, diplopia, limb weakness, or language disturbance (e.g., anomia) excludes Bell's palsy and indicates stroke or brainstem pathology requiring urgent imaging 1, 3, 4
• Bilateral facial weakness: Extremely rare in Bell's palsy; suggests Guillain-Barré syndrome, Lyme disease, or sarcoidosis 2
• Recurrent paralysis on same side: Requires MRI to exclude tumor 1, 2
• Ear symptoms: Vesicles suggest Ramsay Hunt syndrome (herpes zoster); chronic otitis or cholesteatoma may cause facial palsy 2, 5
• Endemic exposure: Lyme disease in endemic areas, especially with bilateral involvement 2

Physical Examination: Distinguish Central from Peripheral

Forehead involvement is mandatory for diagnosing peripheral (LMN) facial palsy—inability to wrinkle forehead or raise eyebrow distinguishes it from stroke, which typically spares the forehead. 1, 2

• Test all cranial nerves systematically: Any additional cranial nerve deficit (CN V, VI, VIII, IX, X, XI, XII) excludes Bell's palsy and mandates urgent MRI 1, 2, 4
• Assess eye closure: Complete inability to close the eye indicates complete paralysis and higher risk of incomplete recovery 6, 1
• Grade severity: Use House-Brackmann scale (Grade 1 = normal to Grade 6 = complete paralysis) to document baseline and track recovery 1
• Test taste: Anterior two-thirds of tongue (chorda tympani branch involvement) 1, 2
• Check for hyperacusis: Indicates proximal facial nerve involvement 1, 2

Diagnostic Testing: What NOT to Order

Do not obtain routine laboratory tests or imaging for typical Bell's palsy presentations—this delays treatment beyond the critical 72-hour window without improving outcomes. 1

• No routine labs: Ordering CBC, metabolic panel, or viral serologies provides no benefit and delays corticosteroid initiation 1
• No routine imaging: CT or MRI is not indicated for classic presentations (rapid onset <72 hours, isolated facial weakness, forehead involved) 1
• No electrodiagnostic testing for incomplete paralysis: ENoG and EMG provide no actionable information when any facial movement remains 6, 1

When Imaging IS Indicated

Order MRI with and without contrast (brain + orbit/face/neck) for: 1, 2

• Recurrent paralysis on same side
• Isolated branch paralysis (e.g., only lower face)
• Other cranial nerve involvement
• No recovery after 3 months
• Progressive weakness beyond 3 weeks
• Bilateral facial weakness
• Forehead sparing (suggests central stroke)
• New or worsening neurologic findings at any time

First-Line Treatment: Corticosteroids

Prescribe prednisolone 50 mg once daily for 10 days OR prednisone 60 mg once daily for 5 days followed by 5-day taper (60→50→40→30→20→10 mg, stop day 11). 1

Evidence for Steroids

• 83% complete recovery at 3 months with prednisolone vs 64% with placebo (NNT = 6) 1
• 94% complete recovery at 9 months with prednisolone vs 82% with placebo (NNT = 8) 1
• Must initiate within 72 hours—no benefit after this window 1

Common Steroid Pitfall

Avoid standard methylprednisolone dose packs—they deliver only ~105 mg prednisone-equivalent total over 6 days, far below the required ~540 mg over 10-14 days, representing significant underdosing. 1

Special Population: Diabetes

Diabetes is NOT a contraindication to corticosteroids—the therapeutic benefit outweighs temporary hyperglycemia risk. 1

• Monitor capillary glucose every 2-4 hours during first few days 1
• Proactively increase basal and prandial insulin 1
• Consider adding NPH insulin concurrent with morning steroid dose (peaks 4-6 hours later, matching hyperglycemic effect) 1

Special Population: Pregnancy

Treat pregnant women with oral corticosteroids within 72 hours after individualized risk-benefit discussion—the same regimen applies. 1

Antiviral Therapy: Limited Role

Never prescribe antivirals alone—they are completely ineffective as monotherapy and delay appropriate steroid treatment. 1

May consider adding valacyclovir 1000 mg TID × 7 days OR acyclovir 400 mg five times daily × 10 days to steroids within 72 hours for severe/complete paralysis, but the added benefit is minimal (96.5% vs 89.7% recovery with steroids alone; absolute benefit +6.8%). 1

• The large BELLS trial (n=496) found no significant advantage: 71% recovery with acyclovir vs 76% without (P=0.50) at 3 months 1
• This is classified as an "option" rather than a recommendation 1

Eye Protection: Prevent Corneal Damage

Implement aggressive eye protection immediately for all patients with impaired eye closure—corneal exposure can cause permanent damage. 1

Daytime Protection

• Lubricating drops every 1-2 hours while awake (e.g., hydroxypropyl methylcellulose) 1
• Sunglasses outdoors to protect from wind and debris 1

Nighttime Protection

• Ophthalmic ointment at bedtime for sustained moisture 1
• Eye taping or patching with careful instruction on proper technique to avoid corneal abrasion 1
• Moisture chambers (polyethylene covers) for severe cases 1

Urgent Ophthalmology Referral

Refer immediately for: 1

• Severe impairment with complete inability to close eye
• Eye pain, vision changes, redness, discharge
• Signs of corneal exposure or damage
• Persistent lagophthalmos beyond 3 months

Electrodiagnostic Testing: Limited Indications

Offer electrodiagnostic testing ONLY to patients with complete facial paralysis, performed 3-14 days after symptom onset (before 7 days or after 14-21 days is unreliable due to ongoing Wallerian degeneration). 6, 1

Interpretation

• ENoG >10% amplitude compared to unaffected side: excellent prognosis, most recover normal function 6, 1
• ENoG <10% amplitude: up to 50% risk of incomplete recovery 6, 1
• EMG may provide additional information when ENoG shows <10% function 6

Do not perform electrodiagnostic testing for incomplete paralysis—it provides no actionable information. 1

Therapies NOT Recommended

• Physical therapy: No proven benefit over spontaneous recovery 1, 2
• Acupuncture: Poor-quality evidence, indeterminate benefit-harm ratio 1, 2
• Surgical decompression: Rarely indicated except in highly selected cases at specialized centers 1

Mandatory Follow-Up and Referral Triggers

Refer to facial nerve specialist or reassess urgently for: 1

• Incomplete facial recovery at 3 months after symptom onset
• New or worsening neurologic findings at any point
• Development of ocular symptoms at any time
• Progressive weakness beyond 3 weeks (suggests alternative diagnosis)

Long-Term Complications Requiring Specialist Management

Approximately 30% of patients experience permanent facial weakness requiring: 1

• Reconstructive surgery: Static procedures (eyelid weights, brow lifts, facial slings) or dynamic procedures (nerve transfers) 1, 7
• Persistent eye closure problems: Tarsorrhaphy or eyelid weight implantation 1
• Psychological support: Depression screening and referral for quality-of-life issues 1

Pediatric Considerations

Children have better prognosis with higher spontaneous recovery rates than adults. 1

• Steroid benefit in children is inconclusive (no high-quality pediatric trials exist) 1
• May consider prednisolone 1 mg/kg/day (max 50-60 mg) for 5 days + 5-day taper for severe cases after shared decision-making with caregivers 1
• Same 72-hour treatment window applies 1
• Same follow-up triggers: Reassess at 3 months if incomplete recovery, or urgently for new neurologic findings or ocular symptoms 1

Prognosis

• Incomplete paralysis: Up to 94% complete recovery 6, 1
• Complete paralysis: ~70% complete recovery within 6 months 6, 1
• Most patients begin recovery within 2-3 weeks, with complete recovery typically by 3-4 months 1
• 30% may have permanent weakness with muscle contractures 1

Critical Pitfalls to Avoid

• Delaying steroids beyond 72 hours eliminates therapeutic benefit 1
• Using antivirals alone is completely ineffective 1
• Failing to test forehead function can miss central stroke 1, 2
• Missing additional cranial nerve deficits delays diagnosis of serious pathology 1, 2, 4
• Inadequate eye protection leads to permanent corneal damage 1
• Failing to refer at 3 months delays access to reconstructive options 1
• Ordering unnecessary labs/imaging delays treatment without benefit 1
• Accepting diagnosis without excluding stroke, tumor, Lyme, or Ramsay Hunt can miss serious pathology 2, 5