26th June 2023

A 45-year-old man with a previous history of alcohol excess presents with atraumatic bilateral upper and lower limb pain

A 45-year-old man with a previous history of alcohol excess presents with atraumatic bilateral upper and lower limb pain and urinary incontinence on a background of a year-long history of poor balance and unsteadiness, requiring increased packages of care. He had been seen by his GP previously for the unsteadiness and had been started on vitamin B replacement, his haematinic screen, including B12 and folate, 2 weeks ago, have all been normal. His pupils are not reactive to light stimuli but clearly constrict when testing accommodation.

Which serum test is likely to reveal the source of his pathology?