Review Question - QID 210771

A 55-year-old woman presents to the emergency department for evaluation of headache. She had a headache that was present for a few hours before subsiding 2 days ago, and then today she developed a headache that was sudden in onset and at maximal intensity within minutes. She has never had a headache like this in the past. Her temperature is 99.0°F (37.2°C), blood pressure is 157/99 mmHg, pulse is 90/min, respirations are 16/min, and oxygen saturation is 99% on room air. On exam, she has pain with passive and active movement of the neck. No focal neurologic deficits are appreciated. A non-contrast head CT is obtained as shown in Figure A. Which of the following is the most likely underlying etiology of this patient's headache?