In which condition would you expect to find a 'thunderclap' headache?

A 'thunderclap' headache is a sudden and severe headache that reaches maximum intensity within minutes. This symptom is most characteristic of a subarachnoid hemorrhage, which occurs when there is bleeding in the space surrounding the brain. The rapid onset of such a headache often leads patients to describe it as the "worst headache of their life."

The mechanism behind this type of headache in the case of a subarachnoid hemorrhage involves irritation of the meninges and increased intracranial pressure due to the presence of blood in the cerebrospinal fluid. Patients may also experience neck stiffness, nausea, or altered consciousness due to the neurological implications of the hemorrhage.

In contrast, while a stroke can cause headaches, they typically develop more gradually and are usually accompanied by other neurological symptoms. Migraines, though they can be intense, usually have a more gradual onset and may be accompanied by aura or light sensitivity. Tension headaches are generally mild to moderate in intensity and do not match the severity or rapid onset associated with the thunderclap phenomenon. Hence, a thunderclap headache is most accurately associated with a subarachnoid hemorrhage.