Which cranial nerve innervates the superior oblique muscle, allowing the eye to look downward and inward?

Which cranial nerve innervates the superior oblique muscle, allowing the eye to look downward and inward?

• A. Abducens nerve (CN VI)
• B. Trochlear nerve (CN IV)
• C. Oculomotor nerve (CN III)
• D. Trigeminal nerve (CN V)

Answer: (B)

The nerve that innervates the superior oblique muscle is the trochlear nerve. This muscle is responsible for depressing the eye when it is turned inward (adducted) and it also intorts the eye. That combination of action explains why looking downward and inward relies on the superior oblique. Other cranial nerves don’t supply this muscle: the abducens nerve controls the lateral rectus to move the eye outward, the oculomotor nerve supplies most of the other extraocular muscles and parasympathetic functions, and the trigeminal nerve is involved in facial sensation and chewing muscles, not eye movement.

The nerve that innervates the superior oblique muscle is the trochlear nerve. This muscle is responsible for depressing the eye when it is turned inward (adducted) and it also intorts the eye. That combination of action explains why looking downward and inward relies on the superior oblique.

Other cranial nerves don’t supply this muscle: the abducens nerve controls the lateral rectus to move the eye outward, the oculomotor nerve supplies most of the other extraocular muscles and parasympathetic functions, and the trigeminal nerve is involved in facial sensation and chewing muscles, not eye movement.