Your patient in ED with a head injury develops rhinorrhea. You quickly grab a 4x4 gauze to test the drainage. When you observe the drainage on the gauze, which of the following would indicate a positive Halo sign?

A. Blood covering the whole gauze is incorrect because this suggests active bleeding only. It does not demonstrate separation of cerebrospinal fluid from blood and therefore does not indicate a cerebrospinal fluid leak. B. There will be a circle of blood in the center of the gauze with a yellow ring around it is correct because this finding represents the positive Halo (or ring) sign. When cerebrospinal fluid is mixed with blood, the blood remains concentrated in the center while the clearer CSF migrates outward, forming a yellow or straw-colored ring. This indicates a possible CSF leak, commonly associated with a basilar skull fracture, and is a medical emergency due to the risk of meningitis. C. There will be a greenish-colored fluid present on the gauze is incorrect because CSF is typically clear or straw-colored, not green. Green drainage is more suggestive of infection or purulent nasal discharge rather than a CSF leak. D. There will be multiple circles of blood noted on the gauze is incorrect because multiple blood spots do not demonstrate the characteristic separation pattern seen with CSF. The halo sign specifically involves a central blood spot with a surrounding clear or yellow ring.