No LP if CT Negative Out to 24 Hours?

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When using multislice CT (MSCT) scanners this study suggests it may be possible to extend the timeframe from headache onset within which aneurysmal subarachnoid hemorrhage (aSAH) can be effectively ruled out with imaging alone. They found that when MSCT was employed within 24 hours of symptom onset, the sensitivity of detecting aSAH remained 100%.

Point | Counterpoint – No LP if Negative CT for SAH

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The prevalence of subarachnoid hemorrhage (SAH) for patients presenting with sudden onset headache after a negative head CT is less than 1%, and the time, resources, and risks associated with lumbar puncture (LP) are not insignificant. Therefore, LP may not routinely be needed to rule out SAH after a negative head CT, even if the scan is performed more than 6 hours from symptom onset.

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