You are the clinician at the student-health center at a larg…
You are the clinician at the student-health center at a large university. Josh, a 19-year-old male college student with a history of chronic migraines, has been experiencing a headache and vomiting for about 24 hours. His roommate and friends have not been ill. He and his roommate just returned a day ago, from a 3 day hiking trip to Washington State with his Labrador retriever. His roommate reports that he brought Josh to the clinic because, “he isn’t acting right this morning.” Your exam reveals the following: altered mental status, headache, and vomiting. While having Josh lie flat on his back, you flex the thigh so that it is at a right angle to the trunk (see image below). You note severe hamstring stiffness causing an inability to straighten the leg due to severe pain. Which of the following is the most likely differential diagnosis?