She has no concerns other than the fact that the infant’s left eye does not seem to be as big as the right eye. On exam, you notice a very faint lid crease, eyelid lag on downgaze, barely visible corneal reflex, and poor elevation of the upper lid on the left side. The rest of the exam, including pupils and extraocular movements, is normal.
The child most likely has:
A. Congenital cranial nerve (CN) III palsy.
B. Congenital ptosis.
C. Congenital Horner syndrome.
D. Acquired aponeurotic ptosis.
E. Marcus Gunn jaw-winking syndrome.
The correct answer is “B.” Congenital ptosis is secondary to levator muscle dysgenesis (myogenic etiology). The etiology of acquired ptosis is diverse and includes aponeurotic defects, CN III palsy, Horner syndrome, ocular myopathies, myasthenia gravis, and synkinetic neurogenic syndromes such as Marcus Gunn jaw-winking syndrome. The most common cause of acquired ptosis is aponeurotic, with defects at the origin or insertion of the aponeurosis. The distinction between congenital myogenic ptosis (simple congenital ptosis) and acquired aponeurotic ptosis can be made with the clinical observation of a weak or absent lid crease, which would be observed in congenital ptosis. In contrast, in cases of acquired ptosis, the lid crease is higher than normal. The levator function is reduced in congenital ptosis and near normal in acquired aponeurotic ptosis. Lastly, there is eyelid lag in downgaze with congenital myogenic ptosis and eyelid drop (ie, worsening of the ptosis when looking down) in acquired aponeurotic ptosis.