<prompt> Halo sign is positive and handkerchief test is negative in:CSF RhinorrhoeaDeted nasal septumNasal MyiasisChoanal atresia  <response>: To distinguish CSF rhinorrhoea from simple rhinorrhoea of rhinitis the following tests can be done: 1Handkerchief test:Mucus stiffens the handkerchief but CSF does not. 2Halo signTarget sign: This test is useful when CSF rhinorrhoea is associated with epistaxis in the immediate period after trauma. A drop is put on Whatmans filter paper. The blood in the drop produces a central circle and if CSF is present in the drop it produces a halo around the blood circle. 