Features of CSF rhinorrhea:
-Reservoir sign - In CSF rhinorrhea, the fluid which had collected in the sinuses, particularly sphenoid, empties into the nose.
-Double target sign or Halo sign or Target sign: CSF is mixed with blood and collected on a piece of filter paper. It shows a central red spot (blood) and a peripheral lighter halo.
-CSF can’t be sniffed back.
-CSF doesn’t stiffen the handkerchief.
Note: Reservoir sign is also seen in acute mastoiditis/ coalescent mastoiditis where mastoid acts as a reservoir of pus and pus reappear in EAC immediately after cleaning.