MARCUS GUNN PHENOMENON AND ITS VARIANTS

MARCUS GUNN PHENOMENON:

• Elevation of ptotic lid with movement of jaw.
• Due to aberrant connection between 3rd nerve and mandibular division of 5th nerve.
• More common on left side.
• May be associated with superior rectus weakness.
• Grading : 

                          Mild- <2mm elevation of ptotic lid.
                          Moderate- 3-6 mm elevation of ptotic lid.
                          Severe- >= 7 mm elevation of ptotic lid.

INVERSE MARCUS GUNN PHENOMENON:

• Increase in ptosis on jaw movement.
• Due to synkinesis between pterygoids (5th nerve) and orbicularis (7th nerve).
• Also known as ATOIN SYNDROME.

REVERSE MARCUS GUNN PHENOMENON :

• Lateral displacement of jaw on touching cornea.
• Due to synkinesis between ophthalmic division (I) and mandibular division (III) of 5th nerve.
• Seen in supranuclear 5th nerve palsy.