First10 EM - By Justin Morgenstern - September 21, 2020
"Summary
A plain CT head misses very few cases of subarachnoid hemorrhage, even if that CT was done more than 6 hours after symptom onset. The miss rate of a CT done within 6 hours is close to 2 in 1,000. Even if the CT was done after 6 hours, post-test probability is less than 1%. Considering the harms of lumbar puncture, it is clear that the test should not be performed routinely if subarachnoid hemorrhage is the only concern. Of course, there is a much broader differential for a patient with a severe headache, so lumbar puncture will remain a part of the work-up for many patients, based on physician judgement, and hopefully involving patients as part of shared decision making"