Features of a thunderclap headache:
(1) headache with an acute onset
(2) very severe, with maximum intensity at onset ("out of the blue, like a clap of thunder")
Causes of a thunderclap headache:
(1) subarachnoid hemorrhage (ruptured berry aneurysm, etc)
(2) unruptured or leaking cerebral aneurysm ("sentinel" headache)
(3) acute hypertensive crisis
(4) intracranial infection
(5) colloid cyst of the third ventricle
(6) spontaneous intracranial hypotension
(7) dissection of the cervical artery
(8) cerebral venous sinus thrombosis (CVST)
(9) pituitary apoplexy
(10) Vogt-Koyanagi-Harada (VKH) disease
(11) retroclival hematoma
(12) ischemic stroke
(13) reversible cerebral vasoconstriction syndrome (RCVS)
(14) idiopathic or primary
Idiopathic or primary thunderclap headache:
(1) may follow a Valsalva maneuver, sexual activity, exertion or strenuous exercise.
(2) may be associated with diffuse segmental cerebral vasospasm.
