CSF Otorrhea Workup

Updated: Jun 16, 2020
  • Author: Matthew B Hanson, MD; Chief Editor: Arlen D Meyers, MD, MBA  more...
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Workup

Laboratory Studies

See the list below:

  • Unless the source is obvious, such as in a case of recent surgery or trauma, attempt to document that the draining fluid is in fact CSF.

    • Testing the fluid for glucose level helps to distinguish spinal fluid from nasal secretions, which are low in glucose. Contamination of the specimen with blood, serum, tears, or saliva may lead to a false-positive result.

    • Testing for beta2 transferrin, a substance found only in CSF, may identify the true nature of the substance with a greater degree of certainty. Beta2 transferrin is also found to a lesser degree in perilymph, but perilymph would not be expected to cause a large volume of leakage. However, the test for beta2 transferrin may not be readily available and the result may not be returned for days to weeks.

Next:

Imaging Studies

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  • Localization of an otogenic spinal fluid leakage is usually accomplished using imaging studies.

  • Obtain a high-resolution CT scan with axial and coronal sections. Unless an otologic source is certain, the scan should cover all 3 cranial fossae.

    • Check the otic capsule for abnormal morphology, such as a Mondini deformity. Note the sizes of the vestibular and cochlear aqueducts. Check the tegmen plates of the posterior and middle fossae for defects.

    • Localization of leakage sites with CT scanning may be enhanced with the use of intrathecal contrast, such as iopamidol or iohexol.

    • The presence and location of pneumocephalus on CT scanning may help to identify and localize a CSF leak.

  • MRI may be helpful in pinpointing the site of a leak. [3]

    • Spinal fluid, bright on T2 sequences, may be observed entering the middle ear.

    • In cases where a tegmen defect is observed on CT scanning, MRI may demonstrate whether or not brain tissue is prolapsed into the middle ear. Because this is important information for surgical planning, an MRI is a critical adjunct when a defect is found in the bony plate of the tegmen or the posterior fossa.

    • A partially empty sella has recently been recognized as a possible sign of increased intracranial pressure. The increased CSF pressure causes infiltration of the sella with CSF and displacement of the pituitary tissue. This finding, previously thought to be unrelated and incidental, has been shown to occur in 71% of patients with spontaneous CSF leaks.

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