Topic: Subarachnoid Hemorrhage
Subject: Medicine
A 36-year-old female presents with the sudden onset of severe headache, nausea, and photophobia. Her level of consciousness is progressively diminishing. Which one of the following would be the most appropriate next step?

The first study ordered in any patient with suspected subarachnoid hemorrhage should be a head CT without contrast. It will reveal subarachnoid hemorrhage in 100% of cases within 12 hours of the bleed, and it is useful for identifying other sources for the headache, for predicting the site of the aneurysm, and for predicting cerebral vasospasm and poor outcome. As blood is cleared from the affected area, CT sensitivity drops to 93% within 24 hours, and to 50% at 7 days. Patients with a positive CT result for subarachnoid hemorrhage should proceed directly to angiography and treatment. Patients with a suspected subarachnoid hemorrhage who have negative or equivocal results on head CT should have a lumbar puncture. MRI and CT with contrast are not used for the diagnosis of acute subarachnoid hemorrhage.