UMEM Educational Pearls

Category: Neurology

Title: Is That a CSF Leak?

Keywords: cerebrospinal fluid, rhinorrhea, otorrhea, halo, double ring, beta-2 transferrin (PubMed Search)

Posted: 8/12/2020 by WanTsu Wendy Chang, MD (Updated: 8/13/2022)
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  • Spontaneous cerebrospinal fluid (CSF) rhinorrhea is rare and usually related to a combination of thinning of the bone and dura and fluctuating intracranial pressure.
  • CSF rhinorrhea can be associated with idiopathic intracranial hypertension, skull base tumors, neurosurgical and otolaryngology procedures, and trauma.
  • Trauma with fracture of the anterior skull base is the most common cause of CSF rhinorrhea.
  • CT and MRI can identify bony defects, whereas cisternography can diagnose occult leaks.
  • Fluid containing CSF is classically described to make a “halo” or “double-ring” pattern on gauze or linen.

  • However, this sign is not specific to CSF, as mixtures of blood with saline, tears, or rhinorrhea can also produce halos.
  • Beta-2 transferrin is a protein found almost exclusively in CSF* thus can be used to diagnose CSF rhinorrhea.

Bottom Line: Beta-2 transferrin is more accurate than the halo sign to identify CSF containing fluid.

Beta-2 transferrin is found in low concentrations in the perilymph in the cochlea, and aqueous and vitreous humor of the eye



  • Chen GY, Ma L, Xu ML, et al. Spontaneous cerebrospinal fluid rhinorrhea. Medicine (Baltimore). 2018;97(5):e9758.
  • Sunder R, Tyler K. Basal skull fracture and the halo sign. CMAJ. 2013;185(5):416.
  • Warnecke A, Averbeck T, Wurster U. Diagnostic relevance of B2-Transferrin for the detection of cerebrospinal fluid fistulas. Arch Otolaryngol Head Neck Surg. 2004;130(10:1178-84.

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