AMCmiddle twist
A 49-year-old man develops abrupt retro-orbital pain and vomiting while exercising. In the next hour he becomes drowsy and develops left ptosis with limitation of eye movements. He is afebrile, with a blood pressure of 88/54 mmHg and a blood glucose concentration of 2.8 mmol/L (reference range 3.5–7.8); serum sodium is 126 mmol/L (reference range 135–145). Which one of the following is the most likely diagnosis?