During a stroke assessment, which of the following symptoms would be most concerning?

A sudden headache with no prior history is particularly concerning during a stroke assessment because it can indicate the presence of a hemorrhagic stroke, such as a subarachnoid hemorrhage. This type of headache, often described as a "thunderclap" or the "worst headache of one's life," may signal a serious and potentially life-threatening condition that requires immediate medical attention.

While slurred speech without facial droop, temporary loss of vision, and generalized weakness are all significant symptoms that may suggest a stroke or transient ischemic attack (TIA), they generally indicate ischemic processes or less acute situations when compared to the sudden onset of a severe headache. In the context of stroke assessment, the presence of a severe headache without prior history is a red flag that warrants prompt investigation for underlying causes such as vascular abnormalities or hemorrhage, thus making it the most alarming symptom to recognize in this scenario.