A 32-year-old man presents to the Emergency department with a three-day history of paraesthesia in his feet and hands. He has also noticed weakness in his thighs, particularly when walking down stairs, and weakness affecting his shoulders. Prior to this, he had been well, except for a mild case of gastroenteritis after eating Chinese food. On examination, he appears anxious, but cranial nerve examination and fundoscopy are normal. Upper limb examination reveals reduced tone and absent reflexes bilaterally at both wrists. Lower limb examination shows 2/5 power, absent reflexes, and reduced sensation affecting both feet. A lumbar puncture is performed, yielding the following results: opening pressure 14 cmH2O (5-18), CSF protein 0.40 g/L (0.15-0.45), CSF white cell count 4 cells per ml (<5 cells), CSF red cell count 2 cells per ml (<5 cells), and negative CSF oligoclonal bands. What is the diagnosis for this patient?