Which cranial nerves must be damaged to produce strabismus?

Which cranial nerves must be damaged to produce strabismus?

• A. Cranial nerves II and III
• B. Cranial nerves I and II
• C. Cranial nerves IV and VI
• D. Cranial nerves III and VII

Answer: (C)

Strabismus occurs when the muscles that move the eyeball are not functioning in coordinated harmony due to damage to the nerves that supply them. The eye’s movements are controlled by three cranial nerves: III, IV, and VI. The pair in this question targets two muscles that are critical for directing the eye: the superior oblique and the lateral rectus. The trochlear nerve supplies the superior oblique, and the abducens nerve supplies the lateral rectus. If both are damaged, the eye loses two major directions of movement, leading to misalignment between the eyes as they try to look in different directions, which is the hallmark of strabismus. The other pair includes either sensory pathways or nerves that don’t jointly innervate the primary eye muscles responsible for alignment, so they wouldn’t explain the typical motor basis of strabismus.

Strabismus occurs when the muscles that move the eyeball are not functioning in coordinated harmony due to damage to the nerves that supply them. The eye’s movements are controlled by three cranial nerves: III, IV, and VI. The pair in this question targets two muscles that are critical for directing the eye: the superior oblique and the lateral rectus. The trochlear nerve supplies the superior oblique, and the abducens nerve supplies the lateral rectus. If both are damaged, the eye loses two major directions of movement, leading to misalignment between the eyes as they try to look in different directions, which is the hallmark of strabismus. The other pair includes either sensory pathways or nerves that don’t jointly innervate the primary eye muscles responsible for alignment, so they wouldn’t explain the typical motor basis of strabismus.