Headache Test - University of Virginia

He denies photophobia, phonophobia, nausea or vomiting, chest pain, blurred vision or shortness of breath. He has no other symptoms. On examination he is afebrile with a blood pressure of 170/95 and no neck stiffness. The rest of the examination including a full neurological examination is normal. What is the most likely cause of his headache? ................
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