A sudden “worst headache of one’s life” that peaks within an hour — go to the ER for a head CT right away
The key point isn’t how intense the pain is, but how quickly it reaches its peak. In 2,131 people experiencing severe headaches that peaked within an hour, 6.2% had a ruptured blood vessel on the surface of the brain. Anyone aged 40 or older, with neck pain or stiffness, who was seen collapsing by others, whose headache started during physical activity, came on suddenly like an explosion, or has limited neck flexion when examined should go to the ER for a head CT. The vast majority of people who get tested end up fine, but missing even one case of bleeding can be fatal.
An emergency visit itself costs very little. A head CT in…
Ten Canadian emergency departments conducted a prospective cohort study on 2,131 patients with “severe headach…
An emergency visit itself costs very little. A head CT in the ER typically runs a few hundred yuan.
Ten Canadian emergency departments conducted a prospective cohort study on 2,131 patients with “severe headaches peaking within an hour.” They defined clear criteria upfront and tracked outcomes accordingly. Of these, 132 patients (6.2%) had subarachnoid hemorrhage, meaning a ruptured surface blood vessel in the brain. The Ottawa SAH rule includes six criteria: age 40 or older, neck pain or stiffness, witnessed loss of consciousness, onset during physical activity, sudden explosive onset of pain, and limited neck flexion on physical exam. Meeting any one of these criteria triggers a CT scan. This rule identified every single patient with bleeding, with 100% sensitivity. The 95% confidence interval for this figure is 97.2%–100.0%. The trade-off is that only 15.3% of people without bleeding were excluded by this rule (specificity of 15.3%).
Perry JJ, Stiell IG, Sivilotti MLA, et al. (2013). Clinical decision rules to rule out subarachnoid hemorrhage for acute headache. JAMA, 310(12), 1248-1255. https://doi.org/10.1001/jama.2013.278018
Open source linkIt’s not “how painful it is” that matters, but “how fast it reaches peak pain.” Headaches that erupt within seconds to a minute are the real warning sign; gradually worsening migraines are not. Additional symptoms like vomiting, neck stiffness, light sensitivity, or brief fainting also warrant immediate attention. With a specificity of just 15.3%, most people who follow this rule end up with normal results. Yet missing even one case of bleeding can be fatal, so getting tested is absolutely worthwhile. Do not take painkillers to mask the pain and then fall asleep.