We encounter one of these at least every week, so the question of how much diagnostics to order after a painstakingly thorough history and a complete physical including fundoscopy is quite important. Obviously, CT and a spinal tap is always necessary, but then what? I think, the minimum in fact includes CT-angiography (using a delay of 8-10s) to image both arteries and veins, in order to rule out SVT and RCVS (both of which are highly relevant). In addition, I recommend a follow-up MRI after discharge from the ER.
We discuss the differential, consisting of at least:
- SAH/sentinel headache
- ICH and other bleeds (retroclival hematoma)
- Pituitary apoplexy
- a lot of zebras, such as third ventricle colloid cyst, MI, Takotsubo, …
As a reference I recommend this article by Ducros of 2013 (he seems to be an authority on this topic as well as RCVS).