Q: 29 year old female with previous history of Migraine presented with 'sudden onset' of headache. CT scan reported normal. ER called you to evaluate patient before discharging her to follow up as an outpatient, as patient continue to insist that this headache is different from her migraine and is worse headache of her life. Your next step?
Answer: Lumbar puncture
If patient's clinical history match with subarachnoid hemorrhage, lumbar puncture becomes mandatory if CT scan is negative. Xanthochromic supernatant in CSF is highly diagnostic of SAH.