What findings characterize abducens nerve (CN VI) palsy?

• A. Inability to abduct the affected eye; horizontal diplopia worse on gaze toward the affected side.
• B. Ptosis with miosis.
• C. Impaired accommodation with preserved motility.
• D. Ptosis and facial numbness.

Answer: (A)

Abducens nerve palsy directly affects the lateral rectus, the muscle that pulls the eye outward. When this nerve is impaired, the eye cannot abduct, so the eye drifts medially due to the unopposed action of the medial rectus. This produces horizontal diplopia that is most noticeable when trying to gaze toward the affected side, because that direction requires proper lateral movement that the damaged nerve can’t perform.

Understanding this helps distinguish it from other findings: ptosis with miosis points to Horner syndrome (sympathetic pathway disruption) rather than a motor CN VI issue; impaired accommodation with preserved motility isn’t a CN VI problem; and ptosis with facial numbness suggests a broader or different cranial nerve involvement. The key takeaway is the loss of lateral gaze causing horizontal double vision, worse when looking toward the side of the lesion.