3rd January 2024

A 53-year-old male presents to the emergency department with a 6-hour history of sudden onset diplopia

A 53-year-old male presents to the emergency department with a 6-hour history of sudden onset diplopia. On examination, there is no hemiplegia or facial droop, but you note the eye movements are not equal, there is a nystagmus in the right eye on right gaze, and the left eye is not able to fully adduct. There is no pupil abnormality. Which structure has likely been affected?

Select the SINGLE most appropriate option from the list below. Select ONE option only.