Suspect a SAH “warning leak” in any patient with an acute headache and both of the following parameters:
- New onset of the “worst headache ever;” AND
- Sudden Onset: Pain reaches maximal intensity immediately, within 1-2 minutes. Called “thunderclap.”
A non-contrast head CT is 100% sensitive within the first 12 hours, over 90% within the first 24 hours, but only 60% at one week, as blood is resorbed. Similarly, a lumbar puncture is highly sensitive throughout the first week, much less so after two. If you entertain the diagnosis at all, don’t delay.
Most commonly due to a ruptured cerebral aneurysm, though also AVMs, cocaine/amphetamine use, or even sympathomimetics in appetite suppressants / cold remedies (especially for women). Aneurysm incidence is <1 of 4,000, but very common in polycystic kidney disease; also suspect if a positive family history.
See posting Acute Headache – 1.
DiagnosisDude 