A 59-year-old man comes to the emergency because of severe pain in the lower extremities for the past 2 hours. Examination shows marked muscle weakness of the lower extremities. Pulses are normal bilaterally. He is unable to void despite a strong urge to do so. Insertion of a catheter yields 450 mL. Which of the following is the most likely diagnosis?
Amyotrophic lateral sclerosis
Guillain-Barre syndrome
Neuromyelitis optica
Polymyositis
Prostatic metastases
