MIA 2012: Backes D, et al. Time-dependent test characteristics of head computed tomography in patients suspected of nontraumatic subarachnoid hemorrhage. Stroke. 2012 Aug;43(8):2115-9
Bottom Line 1
- 100% sensitive and specific if < 6 hours from headache onset
- 90% sensitive if after 6 hours
A noncontrast head CT can effectively rule out atraumatic subarachnoid hemorrhage (aSAH) in patients who present with acute headache within six hours after ictus. Those who present outside this time window or present atypically for SAH (ie neck pain) require further workup, including a lumbar puncture.