How do you grade and treat Bell's palsy in an adult patient with no underlying medical conditions?

Grading Bell's Palsy

Primary Grading System

The House-Brackmann (HB) grading system is the standard tool for assessing Bell's palsy severity, ranging from Grade 1 (normal function) to Grade 6 (complete paralysis). 1, 2

House-Brackmann Grading Scale

• Grade 1: Normal facial function with no visible weakness or asymmetry 1
• Grade 2: Slight weakness noticeable on close inspection; complete eye closure with minimal effort; slight asymmetry of smile with maximal effort 1
• Grade 3: Obvious but not disfiguring asymmetry; noticeable difference between sides; slight to no forehead movement; incomplete eye closure; obvious asymmetry with mouth movement 1
• Grade 4: Obvious disfiguring weakness; inability to close eye completely even with maximal effort; severe asymmetry of mouth with movement 1
• Grade 5: Only barely perceptible motion; visible asymmetry at rest with drooping mouth corner and decreased/absent nasolabial fold; incomplete eye closure with only slight lid movement 1
• Grade 6: Complete paralysis with no movement whatsoever; total loss of facial tone with marked asymmetry 1

Alternative Grading Systems

While HB remains the standard, two other validated systems exist:

• Sunnybrook Facial Grading System (SFGS): Shows moderate correlation with HB (r = -0.876); a score ≤68 indicates severe palsy requiring aggressive management 3
• Modified Portmann Scale (MPS): Also demonstrates moderate correlation with HB (r = -0.860); a score ≤16 indicates severe dysfunction 3

The HB system is preferred for clinical practice because it is universally recognized and facilitates communication between specialists. 1, 2

Critical Assessment Components

Forehead Function

• Forehead involvement distinguishes Bell's palsy from stroke - inability to wrinkle forehead on affected side confirms peripheral (Bell's palsy) rather than central (stroke) pathology 1
• Test by asking patient to raise eyebrows and look for asymmetry 2

Eye Closure Assessment

• Evaluate ability to close eye completely with gentle and maximal effort 1, 2
• Incomplete eye closure (lagophthalmos) requires immediate eye protection measures regardless of HB grade 1, 2
• Note: The numeric HB grade alone is insufficient for predicting corneal risk - direct measurement of lagophthalmos is more reliable 4

Mouth Movement

• Assess symmetry when smiling, showing teeth, and puffing out cheeks 2
• Observe for drooping of mouth corner and loss of nasolabial fold at rest 1

Additional Features to Document

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

Prognostic Implications by Grade

Favorable Prognosis (Grades 1-3)

• Incomplete paralysis predicts up to 94% complete recovery 2, 5
• Most patients begin recovery within 2-3 weeks 2
• Complete recovery typically occurs within 3-4 months 2

Guarded Prognosis (Grades 4-6)

• Complete paralysis carries approximately 70% complete recovery rate 2, 5
• 30% risk of permanent facial weakness with muscle contractures 1, 2
• Consider electrodiagnostic testing (ENoG/EMG) at 3-14 days post-onset for prognostic information 2
• ENoG showing <10% nerve response amplitude compared to unaffected side indicates up to 50% risk of incomplete recovery 2

Treatment Algorithm Based on Grade

All Grades (Within 72 Hours of Onset)

Prescribe oral corticosteroids immediately: prednisolone 50 mg daily for 10 days OR prednisone 60 mg daily for 5 days followed by 5-day taper 1, 2

• Evidence shows 83% recovery at 3 months with steroids vs 63.6% with placebo 1, 2
• Treatment beyond 72 hours shows no proven benefit 2

Optional Addition for All Grades

• Consider adding antiviral therapy (valacyclovir 1g three times daily for 7 days OR acyclovir 400mg five times daily for 10 days) to steroids 2, 5
• Combination therapy shows 96.5% complete recovery vs 89.7% with steroids alone, though benefit is small 1
• Never prescribe antivirals alone - they are ineffective as monotherapy 1, 2

Eye Protection (Grades 3-6 with Incomplete Eye Closure)

Implement immediately to prevent permanent corneal damage: 1, 2

• Lubricating drops every 1-2 hours while awake 2
• Ophthalmic ointment at bedtime 2
• Eye taping or patching at night (with careful instruction to avoid corneal abrasion) 1, 2
• Sunglasses outdoors 1, 2
• Urgent ophthalmology referral for complete inability to close eye 2

Electrodiagnostic Testing (Grade 6 Only)

• Offer ENoG/EMG to patients with complete paralysis 2
• Perform between 3-14 days post-onset for reliable prognostic information 2, 6
• Testing before 7 days or after 14-21 days may be unreliable due to ongoing Wallerian degeneration 2

Mandatory Reassessment Triggers

Refer to facial nerve specialist or reassess immediately if: 1, 2

• Incomplete facial recovery at 3 months post-onset 1, 2
• New or worsening neurologic findings at any point 1, 2
• Development of ocular symptoms at any point 1, 2
• Progressive weakness beyond 3 weeks (suggests alternative diagnosis) 2

Critical Pitfalls to Avoid

• Failing to test forehead function leads to missed stroke diagnosis - central facial weakness spares the forehead 1
• Relying solely on HB grade for eye protection decisions - directly measure lagophthalmos and upper lid closure instead 4
• Delaying corticosteroid treatment beyond 72 hours - effectiveness drops significantly 1, 2
• Prescribing antivirals alone - completely ineffective without steroids 1, 2
• Missing bilateral involvement - extremely rare in Bell's palsy and should trigger investigation for Lyme disease, sarcoidosis, or Guillain-Barré syndrome 1, 7
• Accepting recurrent episodes as "Bell's palsy" - recurrence requires imaging and workup for underlying etiology (tumor, sarcoidosis, Lyme disease, diabetes) 7