A patient with basilar skull fracture has clear fluid dripping from the nose. When the fluid falls onto a white gauze piece, it produces a central blood-stained spot surrounded by a lighter yellowish ring. This finding indicates that the fluid is:

• A Thin serous nasal discharge
• B Pure venous blood
• C Cerebrospinal fluid mixed with blood ✓
• D Purulent rhinorrhoea

Explanation

The double-ring or target sign appears when CSF containing blood is dropped onto filter paper or gauze: blood concentrates centrally while CSF spreads further out as a pale halo, because CSF has lower surface tension and viscosity than blood. It supports a traumatic CSF fistula. Confirmation can be done by testing for beta-2 transferrin or glucose, though glucose alone gives false positives with lacrimal secretions.

Reference: Dhingra's Diseases of Ear, Nose and Throat, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.