What are the typical physical exam findings in Bell's palsy?

Physical Exam Findings in Bell's Palsy

Bell's palsy presents with acute unilateral facial nerve paresis or paralysis with onset in less than 72 hours without an identifiable cause, characterized by rapid onset of unilateral facial weakness or paralysis involving the forehead. 1

Key Physical Examination Findings

• Facial Weakness/Paralysis: Unilateral weakness or complete inability to move facial muscles on the affected side, with involvement of the forehead (distinguishing it from central causes of facial weakness) 2

• Grading of Severity: The House-Brackmann facial nerve grading system is commonly used to assess severity 2:

  • Grade 1: Normal facial function
  • Grade 2: Mild dysfunction with slight weakness noticeable only on close inspection
  • Grade 3: Moderate dysfunction with obvious but not disfiguring difference between sides
  • Grade 4: Moderately severe dysfunction with obvious weakness/disfiguring asymmetry
  • Grade 5: Severe dysfunction with barely perceptible motion
  • Grade 6: Total paralysis with loss of tone and no motion 2

• Eye Findings: Inability to close the eyelid completely (lagophthalmos), which may lead to corneal exposure and damage 1

• Mouth Findings: Drooping of the corner of the mouth, decreased or absent nasolabial fold, and difficulty with oral competence leading to drooling 2, 3

• Bell's Phenomenon: Upward and outward movement of the eye when attempting to close the affected eyelid 1

Associated Symptoms on Examination

• Pain: Ipsilateral pain around the ear or face may be present as a presenting symptom 2

• Hyperacusis: Increased sensitivity to sound due to stapedius muscle involvement 2

• Taste Disturbance: Altered or diminished taste on the anterior two-thirds of the tongue due to chorda tympani involvement 2

• Dry Eye/Mouth: Decreased tear and saliva production due to autonomic fiber involvement 2

Distinguishing Features from Other Causes of Facial Weakness

• Forehead Involvement: In Bell's palsy, the forehead is affected (inability to raise eyebrow), unlike in central causes of facial weakness where forehead is typically spared 4

• Acute Onset: Symptoms develop rapidly over 24-72 hours 2, 5

• No Other Neurological Deficits: Absence of other cranial nerve involvement or neurological abnormalities 4

Red Flags on Examination That Suggest Alternative Diagnosis

• Bilateral Facial Weakness: Bell's palsy is typically unilateral; bilateral involvement is rare and suggests alternative diagnosis 2

• Isolated Branch Paralysis: Involvement of only specific branches of the facial nerve suggests an alternative diagnosis 1

• Other Cranial Nerve Involvement: Presence of additional neurological deficits beyond the facial nerve suggests an alternative diagnosis 1

• Gradual Progression Beyond 3 Weeks: Bell's palsy typically reaches maximum weakness within days; prolonged progression suggests alternative diagnosis 5, 6

Examination Approach

• Assess all facial movements systematically:

  • Raise eyebrows (frontalis)
  • Close eyes tightly (orbicularis oculi)
  • Smile and show teeth (zygomaticus, risorius)
  • Purse lips (orbicularis oris)
  • Puff out cheeks 2

• Evaluate eye closure carefully to assess risk of corneal exposure 1

• Test taste on anterior two-thirds of tongue if equipment available 2

• Check for hyperacusis by testing sound sensitivity 2

Pitfalls in Physical Examination

• Failing to Test Forehead Function: Critical to distinguish Bell's palsy from central causes of facial weakness 4

• Missing Subtle Weakness: Early or mild cases may show only slight asymmetry requiring careful inspection 2

• Inadequate Eye Assessment: Failure to properly assess eye closure can lead to missed corneal protection needs 1

• Not Recognizing Atypical Features: Features like bilateral involvement, isolated branch weakness, or other cranial nerve involvement should prompt consideration of alternative diagnoses 2, 1