25th June 2023

A 28-year-old man presents with a headache and complains of double vision. He has a long history of migraines

A 28-year-old man presents with a headache and complains of double vision. He has a long history of migraines and reports this current headache is similar but seems focused around his left eye. On examination, he reports diplopia, especially on gazing to the left and downwards. His observations are otherwise within normal limits, with no pyrexia and no other neurological signs. He mentions having been pushing himself hard at the gym to prepare for a weightlifting competition and had a recent car accident for which he did not seek medical attention having only suffered a temporary ‘whiplash’.

Based on his likely diagnosis, what is the most appropriate investigation?