Which symptom is most suggestive of a subarachnoid hemorrhage?

The symptom "The worst headache I have ever had" is particularly indicative of a subarachnoid hemorrhage because it characteristically presents as a sudden and severe headache, often described by patients as a rupture of a cerebral aneurysm. This type of headache is referred to as a "thunderclap headache" and typically reaches peak intensity within minutes. It is a hallmark symptom that raises suspicion for a subarachnoid hemorrhage, prompting immediate medical evaluation and intervention.

In contrast, persistent cough and gradual onset of dizziness do not align with the acute presentation typically seen in subarachnoid hemorrhage. A sudden loss of vision may suggest other neurological events, such as a retinal detachment or stroke, but it is not specific to subarachnoid hemorrhage. Therefore, the sudden onset and intensity of the headache in this scenario make it the most suggestive symptom of a subarachnoid hemorrhage.