37 year old male is in the Emergency department. He complains of progressive leg weakness. It started two days ago with tingling in his feet, then his legs became weak. Now he cannot stand on his legs or move. Two weeks ago he had episode of diarrhoea.

Neurological examination: arm strength – 5 pt. (proximal), 4(+) pt. (distal), leg strength – 3 pt. proximal, 2 pt. (distal) after modified MRC scale. Achilles reflexes are absent, patellar – hypoactive. Sense of vibration in the feet is diminished.

Which diagnosis is the most probable?