25th June 2023

A 48-year-old lady presents with severe double vision and vertigo. She also complains of intermittent paraesthesia in her lower limbs

A 48-year-old lady presents with severe double vision and vertigo. She also complains of intermittent paraesthesia in her lower limbs on bending her neck, with the right side being more pronounced than the other. On examination using a penlight, you note pupillary constriction when light is shone in her left eye. Upon moving the penlight to the right eye, the right pupil constricts. However, when the torch is then moved back to the left eye, the left pupil dilates. You also note that she is unable to adduct either eye.

Which structures are likely to be involved in her condition?