Review Question - QID 214205

A 45-year-old man with a past medical history of asthma presents to the expedition physician with a change in his mental status. The patient is on a group hike to ascend a local mountain. His behavior has been strange, and he seems confused. He has had poor oral intake and has only been drinking water. He also endorses a headache and fatigue. On exam, the patient is not answering questions appropriately. He has bilateral wheezing with good air movement. The patient demonstrates a notable ataxic gait and does not follow commands for the rest of his neurologic exam. Which of the following is the most likely diagnosis?