13th August 2020

A 50-year-old male presents to his GP complaining of double vision

A 50-year-old male presents to his GP complaining of double vision. On examination of the eye movements, the GP notes that he has developed a vertical gaze palsy. The GP performs a complete neurological examination and notes cogwheel rigidity in the upper limbs, as well as slowness to initiate standing from a seated position. The man seems unsteady on his feet and almost topples over when gently pulled backwards. He has no past medical history and takes no regular medications.

Select the SINGLE most appropriate investigation from the list below, which would aid in confirmation of this diagnosis. Select ONE option only.