What is the Bell's palsy score and how is it used to assess and treat a patient with Bell's palsy?

Bell's Palsy Scoring Systems

The House-Brackmann Grading Scale (HBGS) is the internationally recognized standard for assessing facial nerve function in Bell's palsy, with six grades ranging from normal function (Grade 1) to complete paralysis (Grade 6), and should be documented at presentation and throughout recovery to guide treatment decisions and prognosis. 1

Primary Grading System: House-Brackmann Scale

The House-Brackmann system provides a straightforward clinical assessment tool that correlates with prognosis and recovery 1:

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

Alternative Grading Systems

While HBGS remains the gold standard, two alternative systems offer more detailed regional assessment 2:

• Sunnybrook Facial Grading System (SFGS): Shows moderate consistency with HBGS (r = -0.876, P < 0.01), with an optimal cut-off value of ≤68 points indicating severe facial nerve palsy 2
• Modified Portmann Scale (MPS): Demonstrates moderate consistency with HBGS (r = -0.860, P < 0.01), with an optimal cut-off value of ≤16 points indicating severe palsy 2
• Facial Nerve Grading System 2.0 (FNGS 2.0): Provides regional assessment of mouth, eyes, and brow with exact agreements of 72%, 63%, and 52% respectively, yielding stricter evaluation than HBGS 3

Clinical Application of Scoring

Document the initial grade within 72 hours of symptom onset to establish baseline severity, as this directly predicts recovery and guides treatment intensity. 1, 4

Prognostic Implications by Grade

• Incomplete paralysis (Grades 1-3): Excellent prognosis with recovery rates up to 94% 4
• Complete paralysis (Grades 5-6): Approximately 70% recovery rate, with up to 50% risk of incomplete recovery if electrodiagnostic testing shows less than 10% nerve function 4
• Approximately 30% of all patients may experience permanent facial weakness with muscle contractures 1, 2, 5

Assessment Timeline and Documentation

Reassess facial nerve function at specific intervals to monitor recovery trajectory and identify patients requiring specialist referral 1, 4:

• Initial visit (within 72 hours): Document baseline HBGS grade, initiate corticosteroids, and establish eye protection measures 1, 4
• 1-2 weeks: Monitor early recovery signs and reinforce eye care 4
• 3 weeks: Most patients begin showing signs of recovery 4
• 3 months: Mandatory reassessment—incomplete recovery at this point requires specialist referral 1, 4
• 6 months: Approximately 70% of patients with complete paralysis achieve full recovery by this timeframe 4, 5

Key Physical Examination Components for Scoring

Document these specific findings to accurately grade severity 1:

• Forehead movement: Ability to raise eyebrows and wrinkle forehead (distinguishes peripheral from central lesions) 1
• Eye closure: Complete versus incomplete, with or without effort, and presence of Bell's phenomenon 1
• Mouth symmetry: Ability to smile, show teeth, and puff out cheeks 1
• Nasolabial fold: Presence, depth, and symmetry 1
• Resting asymmetry: Drooping of mouth corner, eyelid ptosis 1

Associated Features to Document

Beyond motor grading, assess these facial nerve branch functions 1:

• Taste disturbance: Anterior two-thirds of tongue (chorda tympani involvement) 1
• Hyperacusis: Increased sound sensitivity (stapedius muscle involvement) 1
• Dry eye or mouth: Autonomic fiber dysfunction 1
• Ipsilateral ear or facial pain: Common presenting symptom 1

Critical Red Flags Requiring Alternative Diagnosis

Do not diagnose Bell's palsy if any of these atypical features are present 1, 4:

• Bilateral facial weakness: Suggests Lyme disease, sarcoidosis, or Guillain-Barré syndrome 1, 6
• Isolated branch paralysis: Indicates structural lesion requiring imaging 4
• Other cranial nerve involvement: Excludes Bell's palsy and suggests central pathology 1
• Progressive weakness beyond 3 weeks: Requires immediate reassessment for tumor or other pathology 4
• Recurrent paralysis on same side: Warrants MRI to exclude tumor 6, 4

Electrodiagnostic Testing Correlation

Offer electroneurography (ENoG) to patients with complete facial paralysis (Grades 5-6) performed 3-14 days post-onset for prognostic information 4, 7:

• >10% nerve response amplitude: Excellent prognosis for complete recovery 4
• <10% nerve response amplitude: Up to 50% risk of incomplete recovery 4
• Testing before 7 days or after 14-21 days provides unreliable information due to ongoing Wallerian degeneration 4

Treatment Decisions Based on Grading

All grades benefit from immediate corticosteroid therapy within 72 hours, but eye protection intensity varies by severity 1, 4:

• Grades 1-2: Lubricating drops during day, ointment at night 1
• Grades 3-4: Add eye taping/patching at night, sunglasses outdoors 1
• Grades 5-6: Urgent ophthalmology referral, consider moisture chambers, possible tarsorrhaphy or eyelid weights if persistent beyond 3 months 1, 4

Common Pitfalls in Scoring

• Failing to test forehead function: Critical for distinguishing Bell's palsy from stroke, which spares the forehead 1
• Inadequate eye closure assessment: Missing subtle incomplete closure leads to corneal damage 1
• Not documenting initial grade: Prevents accurate assessment of recovery trajectory 4
• Delaying 3-month reassessment: Misses window for reconstructive interventions in incomplete recovery 1, 4