Which of the following describes a sudden severe headache without a known cause?

A sudden severe headache without a known cause is often recognized as a warning sign of a stroke. This type of headache can occur suddenly and is characterized by its intensity, which may feel distinctively different from typical headaches. It raises concern for potential neurological issues, like a hemorrhagic stroke, where bleeding in the brain can lead to increased intracranial pressure and other complications.

This option is particularly significant in healthcare contexts because timely recognition and intervention are crucial for improving patient outcomes in cases of stroke. Not all severe headaches indicate a stroke, but the sudden onset of a very intense headache (often described as "the worst headache of my life") should always be taken seriously and warrants immediate medical evaluation.

The other options do not adequately explain the nature of a sudden severe headache. Normal reactions to stress, common symptoms of dehydration, or signs of fatigue typically present differently and do not have the same level of urgency for medical evaluation as a sudden severe headache does.