A 53-year-old man is brought to the emergency room from the…
A 53-year-old man is brought to the emergency room from the site of an automobile collision. He is conscious but disoriented. The neurological examination shows loss of pain and thermal sensations on the right side beginning at the umbilicus and, loss of vibration and proprioception sense on the left lower limb. The reflexes in the left knee and ankle are brisker than those on the right. Which of the following is the most likely diagnosis of this patient?