Which cranial nerve mediates downward and medial eye movement?

Which cranial nerve mediates downward and medial eye movement?

• A. Optic
• B. Oculomotor
• C. Trochlear
• D. Abducens

Answer: (C)

Downward movement with a medial component is produced by the muscle that pulls the eye down when it is turned toward the nose. This muscle is the superior oblique, and it is innervated by the trochlear nerve. When the eye is adducted (turned inward), the superior oblique depresses the eye and also contributes to inward rotation, giving the downward and medial gaze described. The trochlear nerve is the one that supplies this muscle, making it the best answer. In contrast, the optic nerve carries vision (sensory), the oculomotor nerve innervates most other eye muscles (including those that move the eye medially in a different respect), and the abducens moves the eye laterally.

Downward movement with a medial component is produced by the muscle that pulls the eye down when it is turned toward the nose. This muscle is the superior oblique, and it is innervated by the trochlear nerve. When the eye is adducted (turned inward), the superior oblique depresses the eye and also contributes to inward rotation, giving the downward and medial gaze described. The trochlear nerve is the one that supplies this muscle, making it the best answer. In contrast, the optic nerve carries vision (sensory), the oculomotor nerve innervates most other eye muscles (including those that move the eye medially in a different respect), and the abducens moves the eye laterally.