Oculomotor nerve (CN III) palsy produces which signs?

Oculomotor nerve (CN III) palsy produces which signs?

• A. Ptosis, inability to move the eye normally, and a dilated pupil
• B. Ptosis with preserved pupil constriction
• C. Inability to adduct the eye with normal pupil
• D. Eye movement restricted but pupil is normal

Answer: (A)

Oculomotor nerve palsy affects both eye movement and pupil control because this nerve carries motor fibers to most of the extraocular muscles and levator palpebrae, plus parasympathetic fibers that constrict the pupil. When the nerve is damaged, the eyelid droops (ptosis) from levator weakness, the eye cannot be moved normally in most directions (the eye tends to rest down and out due to unopposed lateral rectus and superior oblique), and if the parasympathetic fibers are involved, the pupil becomes dilated because constriction of the pupil is lost. This combination of ptosis, limited eye movement, and a dilated pupil is the classic presentation of a complete CN III palsy. If the pupil is spared (pupil constriction preserved), you still have ptosis and ophthalmoplegia, but the pupil remains reactive—this distinction helps differentiate full CN III palsy from pupil-sparing variants.

Oculomotor nerve palsy affects both eye movement and pupil control because this nerve carries motor fibers to most of the extraocular muscles and levator palpebrae, plus parasympathetic fibers that constrict the pupil. When the nerve is damaged, the eyelid droops (ptosis) from levator weakness, the eye cannot be moved normally in most directions (the eye tends to rest down and out due to unopposed lateral rectus and superior oblique), and if the parasympathetic fibers are involved, the pupil becomes dilated because constriction of the pupil is lost. This combination of ptosis, limited eye movement, and a dilated pupil is the classic presentation of a complete CN III palsy. If the pupil is spared (pupil constriction preserved), you still have ptosis and ophthalmoplegia, but the pupil remains reactive—this distinction helps differentiate full CN III palsy from pupil-sparing variants.