A

The abrupt “thunderclap” headache with vomiting and nuchal rigidity in a hypertensive elderly patient, in the absence of focal neurological deficits, is classic for aneurysmal subarachnoid hemorrhage; meningitis is usually febrile, ischemic stroke produces focal deficits, and subdural hemorrhage presents more insidiously. [Cohen-Gadol, 2013, PMID 24134085]