A 34-year-old woman presents with painful blurring of vision in her right eye and progressive weakness of both lower limbs for 2 days. She has also had difficulty voiding and began dribbling urine the day before presentation. There is no history of febrile illness, recent vaccination, or ingestion of tinned food.

Her medical history is unremarkable except for an episode of bilateral lower limb weakness 3 months ago, which was of sudden onset and lasted for less than a day. She was diagnosed with a transient ischemic attack, and started on long-term aspirin. The remainder of her stroke work-up, including an MRI brain, was unremarkable.

Her basic laboratory tests including a full blood count, electrolytes, inflammatory markers, renal and liver function tests are unremarkable.