Ptosis means injury to which cranial nerve?

Ptosis means injury to which cranial nerve?

• A. Oculomotor nerve (cranial nerve III)
• B. Optic nerve II
• C. Trochlear nerve IV
• D. Trigeminal nerve V

Answer: (A)

Ptosis, or drooping of the upper eyelid, happens when the muscle that lifts the eyelid, the levator palpebrae superioris, isn’t functioning. That muscle is innervated by the oculomotor nerve, so injury to this nerve leads to eyelid droop. The optic nerve handles vision, the trochlear nerve moves the eye (not the eyelid), and the trigeminal nerve deals with facial sensation and chewing. So the oculomotor nerve is the one whose impairment best explains ptosis.

Ptosis, or drooping of the upper eyelid, happens when the muscle that lifts the eyelid, the levator palpebrae superioris, isn’t functioning. That muscle is innervated by the oculomotor nerve, so injury to this nerve leads to eyelid droop. The optic nerve handles vision, the trochlear nerve moves the eye (not the eyelid), and the trigeminal nerve deals with facial sensation and chewing. So the oculomotor nerve is the one whose impairment best explains ptosis.