22nd February 2024

A 51-year-old patient with multiple sclerosis presents to the eye clinic with a one-week history of double vision, especially when looking downwards in the right eye.

A 51-year-old patient with multiple sclerosis presents to the eye clinic with a one-week history of double vision, especially when looking downwards in the right eye. On examination, there is restriction of the right eye looking down, and a head tilt, consistent with superior oblique impairment. Which cranial nerve is involved?