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ULY CLINIC

26 Septemba 2025, 01:01:53

Marcus Gunn’s phenomenon

Marcus Gunn’s phenomenon is a unilateral reflexive elevation of a ptotic upper eyelid that occurs during movement of the lower jaw, commonly observed in misdirectional cranial nerve syndromes. It reflects abnormal oculomotor (cranial nerve III) and trigeminal (cranial nerve V) interactions.

Pathophysiology

Normal physiology:

The levator palpebrae superioris elevates the upper eyelid under oculomotor nerve control.
The trigeminal nerve controls mastication muscles (masseter, temporalis) without influencing eyelid movement.

Abnormal physiology (misdirectional syndrome):

Aberrant reinnervation or misdirection of nerve fibers causes activation of the levator palpebrae superioris during mandibular movements.
Opening or lateral movement of the jaw triggers reflexive eyelid elevation, producing the characteristic jaw-winking appearance.

Associated findings: May coexist with congenital ptosis, amblyopia, or strabismus on the affected side.

Examination Technique

Patient positioning: Seated comfortably with the face visible.
Observation: Inspect for ptosis at rest and abnormal eyelid movement with jaw activity.
Jaw movements: Ask the patient to open the mouth and move the lower jaw side to side.
Documentation: Record laterality, degree of eyelid elevation, symmetry, and presence of ptosis.

Clinical Features

Feature	Manifestation
Eyelid movement	Reflexive elevation of ptotic upper eyelid during jaw movement
Ptosis	Present at rest on affected side
Trigger	Mouth opening, jaw movement, lateral jaw motion
Laterality	Usually unilateral
Associated ocular findings	Strabismus, amblyopia, or congenital ptosis may co-occur

Differential Diagnosis

Condition	Key Feature	Notes
Marcus Gunn phenomenon	Jaw-winking ptosis, unilateral	Classic misdirectional syndrome
Congenital ptosis	Persistent eyelid droop without jaw movement	No reflexive eyelid elevation
Horner’s syndrome	Ptosis with miosis and anhidrosis	Sympathetic pathway lesion, no jaw-winking
Myasthenia gravis	Variable ptosis, fatigable	Eyelid weakness improves with rest or ice test
Mechanical ptosis	Eyelid droop due to mass or scarring	No reflexive movement

Special populations

Children:

Commonly congenital; early recognition is important to prevent amblyopia and plan corrective surgery if needed.

Adults:

Rarely acquired; usually linked to trauma or aberrant reinnervation.

Limitations

Subtle jaw-winking may be missed if jaw movements are minimal.
Must differentiate from other causes of ptosis or eyelid retraction.
Requires careful observation and patient cooperation.

Patient counseling

Explain that jaw-winking occurs due to abnormal nerve wiring and is not harmful by itself.
Advise ophthalmology referral for assessment of vision, amblyopia risk, and surgical correction if indicated.
Reassure families that the phenomenon is usually congenital and isolated, but may need monitoring.

Conclusion

Marcus Gunn’s phenomenon is a clinical sign of misdirected oculomotor and trigeminal nerve activity, manifesting as reflexive elevation of a ptotic eyelid during jaw movement. Recognition is important for diagnosis, differentiation from other ptoses, and planning ophthalmologic management.

References

Marcus Gunn RM. Ptosis associated with winking of the eyelid on movement of the jaw. Br J Ophthalmol. 1883;67:377–380.
von Noorden GK, Campos EC. Binocular Vision and Ocular Motility: Theory and Management of Strabismus. 6th ed. St. Louis: Mosby; 2002.
Anderson RL, Baumgartner R. Congenital ptosis and Marcus Gunn jaw-winking phenomenon. Ophthalmology. 1991;98:96–101.
Wright KW. Pediatric Ophthalmology and Strabismus. 3rd ed. New York: Springer; 2012.