Clinical Reasoning: A 41-year-old man with thunderclap headache

A 41-year-old man with a history of low testosterone on androgen therapy presented to the emergency department complaining of acute onset of the worst headache of his life. He reported being well until 6 hours earlier, when he was resting in his hotel room and experienced a thunderclap headache. The headache was initially described as retro-orbital, left-sided, associated with vomiting, and extending to the occiput. It was maximal within moments of onset. There were no associated visual complaints, weakness, numbness, or tingling. On initial examination, he was noted to have preserved mental status. The cranial nerve examination showed intact visual fields, normal extraocular motility, and no evidence of papilledema. Sensorimotor function was intact and symmetric throughout, and his gait was stable and narrow-based. Initial laboratory studies including blood count and metabolic panel were unremarkable. He was administered oxygen via nasal cannula, metoclopramide, and diphenhydramine without improvement.