Bell’s sign, also known as Bell’s phenomenon, is defined as reflexive upward and outward deviation of the eyes when the patient attempts to close the eyelids. It is commonly observed on the affected side in Bell’s palsy and indicates supranuclear or peripheral facial nerve dysfunction.

Pathophysiology

• Bell’s sign reflects the protective mechanism of the eye: when eyelid closure is incomplete due to facial nerve (cranial nerve VII) dysfunction, the eyeball moves upward and outward to minimize corneal exposure.

• In Bell’s palsy, peripheral facial nerve lesions impair orbicularis oculi function, preventing effective eyelid closure.

• The phenomenon occurs only when eyelid closure is attempted, indicating a reflexive rather than voluntary eye movement, and helps localize the lesion as supranuclear or infranuclear facial nerve involvement.

Examination Technique

• Patient positioning: Seated or supine, facing the examiner.

• Instruction: Ask the patient to close both eyes tightly.

• Observation:

  • On the affected side, note upward and outward deviation of the eyeball.

  • Assess bilateral comparison to detect asymmetry.

• Interpretation: Presence of upward-outward deviation indicates Bell’s sign, commonly seen in acute facial nerve palsy.

Clinical utility

• Indicator of facial nerve dysfunction: Helps confirm incomplete eyelid closure in Bell’s palsy.

• Protective ocular reflex: Reveals corneal exposure risk that may necessitate eye care interventions.

• Lesion localization: Differentiates supranuclear vs. peripheral facial nerve lesions.

Differential Diagnosis

Management

• Protect the cornea: Use artificial tears, eye ointment, or taping to prevent keratitis.

• Treat underlying cause: Corticosteroids, antiviral therapy (if indicated), and supportive care for Bell’s palsy.

• Monitor recovery: Bell’s phenomenon usually resolves as facial nerve function returns.

• Physical therapy: Facial exercises may aid in muscle strength recovery.

Pediatric considerations

• Bell’s phenomenon may be observed in children with congenital facial palsy.

• Ensure gentle handling and eye protection.

Geriatric considerations

• Older adults with diabetes or hypertension may have slower recovery from Bell’s palsy.

• Eye care is crucial due to increased risk of corneal injury.

Limitations

• Bell’s sign is not pathognomonic for Bell’s palsy; it indicates incomplete eyelid closure, which may occur in other facial nerve disorders.

• Absence of the sign does not rule out facial nerve dysfunction.

Patient counseling

• Explain the purpose of observing eye movement during eyelid closure.

• Emphasize eye protection to prevent dryness or injury.

• Reassure patients about potential for recovery, which is often spontaneous in Bell’s palsy.

Conclusion

Bell’s sign is a classic clinical observation in facial nerve palsy, serving both as a diagnostic clue and an indicator for corneal protection needs. Proper evaluation enhances patient safety and guides supportive management.

References

1. Bell F. A Treatise on the Nerves: Giving an Account of their Structure, Functions, and Diseases. London: Longman, 1821.

2. Buttaro TM, Tybulski J, Bailey PP, Sandberg-Cook J. Primary Care: A Collaborative Practice. St. Louis, MO: Mosby Elsevier; 2008. p. 444–447.

3. McCance KL, Huether SE, Brashers VL, Rote NS. Pathophysiology: The Biologic Basis for Disease in Adults and Children. 8th ed. Maryland Heights, MO: Mosby Elsevier; 2019.

4. Baugh RF, Basura GJ, Ishii LE, et al. Clinical practice guideline: Bell’s Palsy. Otolaryngol Head Neck Surg. 2013;149(3 Suppl):S1–S27.

5. Preston DC, Shapiro BE. Electromyography and Neuromuscular Disorders: Clinical-Electrophysiologic Correlations. 3rd ed. Philadelphia, PA: Elsevier; 2013.