Damage to which nerve would cause the inability to move the eyes laterally?

• A. Cranial nerve III
• B. Cranial nerve IV
• C. Cranial nerve VI
• D. Cranial nerve VIII

Answer: (C)

Lateral gaze is produced by the lateral rectus muscle, which is innervated by the abducens nerve. When this nerve is damaged, the lateral rectus can’t contract, so the eye can’t move outward (abduct). The eye may rest looking inward and diplopia occurs when trying to look to the affected side. The oculomotor nerve controls most other eye muscles, the trochlear nerve controls the superior oblique, and the vestibulocochlear nerve isn’t involved in eye movement. That’s why damage to the abducens nerve best explains an inability to move the eyes laterally.