Would a bleed on the brain ALWAYS show on a CT scan?
NO A sentinel bleed, caused by a tiny rupture of an aneurism (severe headache that comes on) is often invisible on CT scan. That is why an ER doctor will always follow up with a spinal tap if there is any question about a sentinel bleed. The spinal tap will show a few traces of blood in the spinal fluid. The sentinel bleed is small and the headache will go away. However, it is a “sign” that a huge, life threatening bleed is about to take place within a short period of time. That is why a “thunderclap” headache is always evaluated by “CT/LP” which means CT first, and if CT is negative, an LP (spinal tap). I have done this many times, as I used to run an emergency room. Lots of people “these days” (okay, I am an older doc) skip the LP part because it is a hard procedure to do and most of the time it is negative! But I personally am not aware of any new recommendations out there that say not to do the LP. If you had a thunderclap headache and the ER wanted to check for bleeding, ask them
