What is the key examination pearl for a patient presenting with Bell's palsy?

Key Examination Pearl for Bell's Palsy

The critical examination pearl is to verify forehead involvement on the affected side—patients with Bell's palsy cannot wrinkle their forehead or raise their eyebrow on the paralyzed side, which distinguishes peripheral facial nerve palsy from central causes like stroke that spare the forehead. 1, 2

Essential Physical Examination Maneuvers

Forehead Testing (Most Critical)

• Ask the patient to raise both eyebrows or wrinkle their forehead—complete inability on the affected side confirms peripheral facial nerve involvement 1, 2
• Central lesions (stroke) spare the forehead due to bilateral cortical innervation of the upper facial muscles, while Bell's palsy affects all ipsilateral facial muscles 3, 2

Complete Facial Assessment

• Test eye closure by asking the patient to close eyes tightly—incomplete closure with visible sclera (lagophthalmos) indicates severe paralysis and high risk for corneal damage 1, 2
• Observe for Bell's phenomenon: when attempting eye closure, the globe rotates upward and outward as a protective reflex 1
• Ask patient to smile—the mouth pulls only toward the unaffected side with drooping of the corner on the paralyzed side 3
• Have patient puff out cheeks—air leaks from the paralyzed side 1
• Assess nasolabial fold—decreased or absent on affected side at rest 3

Severity Grading

Use the House-Brackmann grading system systematically 1, 2:

• Grade 1: Normal facial function
• Grade 2: Slight weakness noticeable only on close inspection
• Grade 3: Obvious asymmetry but not disfiguring, complete eye closure with effort
• Grade 4: Obvious disfiguring weakness, incomplete eye closure
• Grade 5: Only barely perceptible motion, incomplete eye closure
• Grade 6: Complete paralysis with no movement

Red Flags Requiring Alternative Diagnosis

Neurologic Red Flags

• Forehead sparing suggests stroke—immediately assess for other stroke symptoms 1, 3
• Involvement of other cranial nerves excludes Bell's palsy and suggests brainstem pathology 1, 3
• Bilateral facial weakness is rare in Bell's palsy—consider Lyme disease, sarcoidosis, or Guillain-Barré syndrome 3, 2
• Isolated branch paralysis (not affecting entire hemifacial distribution) suggests tumor or trauma 1

Temporal Red Flags

• Symptom onset exceeding 72 hours suggests alternative diagnosis 3, 2
• Slow progressive worsening beyond initial 72 hours is atypical 2

Associated Findings to Document

• Ipsilateral ear or facial pain is common in Bell's palsy 3, 2
• Hyperacusis (increased sound sensitivity) from stapedius muscle paralysis 1, 2
• Taste disturbance on anterior two-thirds of tongue from chorda tympani involvement 1, 2
• Dry eye or mouth from autonomic fiber involvement 1, 2

Critical Eye Examination

Immediate Assessment

• Measure the palpebral fissure width—widening on affected side indicates lagophthalmos 1
• Test corneal reflex—absent blink response on affected side 1
• Examine for corneal exposure signs: redness, foreign body sensation, or discharge 1
• Any corneal symptoms require urgent ophthalmology referral 1

Eye Protection Urgency

Patients with incomplete eye closure need immediate protective measures initiated at the first visit 1, 2:

• Lubricating drops every 1-2 hours while awake
• Ophthalmic ointment at bedtime
• Eye taping or moisture chamber for severe cases
• Sunglasses outdoors

Common Diagnostic Pitfalls to Avoid

Testing Errors

• Failing to test forehead function is the most common error—this single maneuver distinguishes peripheral from central lesions 1, 3
• Not documenting all other cranial nerves—missing additional deficits delays correct diagnosis 3
• Inadequate eye closure assessment—underestimating corneal exposure risk leads to preventable complications 1, 2

Misdiagnosis Traps

• Assuming stroke because of facial droop without testing forehead—stroke spares the forehead 1, 3
• Missing bilateral involvement by not examining both sides systematically 3, 2
• Overlooking parotid masses or skin lesions suggesting alternative diagnoses 4

Prognostic Physical Findings

Favorable Prognosis Indicators

• Incomplete paralysis (any visible facial movement) predicts up to 94% complete recovery 1, 2
• Ability to partially close eye indicates better prognosis 5

Poor Prognosis Indicators

• Complete paralysis (no visible movement) carries up to 50% risk of incomplete recovery 5, 1
• Complete inability to close eye warrants consideration of electrodiagnostic testing after 7 days 5, 1

Documentation Requirements

Record systematically 1, 2:

• Onset timing (must be <72 hours for Bell's palsy diagnosis)
• Degree of forehead involvement
• Completeness of eye closure
• House-Brackmann grade
• Presence/absence of other cranial nerve deficits
• Associated symptoms (pain, taste changes, hyperacusis)
• Corneal examination findings