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CSF Rhinorrhea Workup

  • Author: Kevin C Welch, MD; Chief Editor: Arlen D Meyers, MD, MBA  more...
 
Updated: May 04, 2016
 

Laboratory Studies

Glucose content

A rapid but highly unreliable test is glucose-content determination with the use of glucose oxidase paper. This method of detecting cerebrospinal fluid (CSF) rhinorrhea is not recommended as a screening or confirmatory laboratory test to detect the presence of CSF in the nasal cavity for the following reasons:

  • Reducing substances present in the lacrimal-gland secretions and nasal mucus may cause false-positive results.
  • Glucose, at a concentration of 5 mg/dL, can lead to a positive result with this test.
  • Active meningitis can lower the glucose level in the CSF and may lead to false-negative readings.
  • This test is not specific for the side or site of leak.

Beta-trace protein [3]

Also known as prostaglandin D synthase, this protein is synthesized primarily in arachnoid cells, oligodendrocytes, and the choroids plexus within the CNS. Beta-trace protein is also present in the human testes, heart, and serum. It is altered by the presence of renal failure, multiple sclerosis, cerebral infarction, and certain CNS tumors. This test has been used to diagnose CSF rhinorrhea in multiple studies, with a sensitivity of 92% and specificity of 100%. This test is not specific for side or site of leak and can be difficult to collect if the leak is intermittent.

Beta2-transferrin

Beta2-transferrin is produced by neuraminidase activity within the central nervous system. Therefore, beta2-transferrin is located only within the CSF, perilymph, and aqueous humor.

The assay has a high sensitivity and specificity, it is performed rapidly, and it is noninvasive. A minimum of 0.5 mL of fluid is necessary for electrophoresis, but difficulties in collection of this fluid have been noted, especially in intermittent, low-volume leaks.

Beta2-transferrin is stable at room temperature for approximately 4 hours; therefore, immediate refrigeration following collection is recommended. Specimens should not be frozen.

This is currently single best laboratory test for identifying the presence of CSF in sinonasal fluid. It should be kept in mind, however, that this test does not provide information regarding the site or laterality of the defect. Not all centers are capable of testing fluid for beta2-transferrin; therefore, sending the laboratory specimen out for processing may delay diagnosis.

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Imaging Studies

Computed tomography (CT) scanning

High-resolution CT scanning is the imaging modality of choice for identifying a skull base defect associated with CSF rhinorrhea. CT scans may demonstrate skull base defects resulting from accidental or iatrogenic trauma, an underlying anatomic or developmental abnormality, or an erosive lesion such as a neoplasm.[4]

CT scans should be performed in the axial plane with 1 mm (or less) slice thickness and reformatted into coronal and sagittal planes. The evaluation of congenital defects or spontaneous defects may be aided by 3-dimensional reconstruction of the bone to permit in-depth analysis of the floor of the anterior or middle cranial fossa.

Pneumocephalus on a CT scan may indicate a dural tear. A deviated crista galli is a radiologic sign in patients presenting with primary CSF rhinorrhea; this finding supports a congenital bony dehiscence as the etiologic basis for this condition. In some circumstances, an air-fluid level is present in one or more of the sinuses. This is not diagnostic of CSF and may be the result of acute or chronic inflammation.

High-resolution CT imaging may reveal defects in the skull base that do not leak or are not sites of active leaking, making the diagnosis more difficult.

CT cisternography[5]

CT cisternography improves the diagnostic yield of plain CT by injecting intrathecal contrast to better localize the site of the CSF leak. As opposed to conventional CT imaging, only one study is typically necessary. CT cisternography depicts the precise location of CSF rhinorrhea in most patients with active leaks. Patients with intermittent CSF rhinorrhea may have false-negative CT cisternograms. Another disadvantage of this technique is that it may miss cribriform or ethmoid sinus defects.

This is an invasive procedure and is not very frequently used. Despite its low morbidity, it can be associated with nausea, headaches, and acute organic psychosyndromes.

Magnetic resonance imaging (MRI)

MRI typically is not recommended as a first-line imaging modality in the evaluation of CSF rhinorrhea unless an encephalocele is demonstrated on examination or is suspected. Unlike CT imaging, MRI does not delineate well bony defects within the anterior or middle cranial fossa. In addition, MRI is more costly and more time consuming. In many instances, the injection of a contrast agent may be necessary. Similar to CT imaging, MRI may not be localizing.

MR cisternography[6]

Avoidance of intrathecal injection of contrast is a key benefit of MR cisternography. T2-weighted imaging can be used to detect the presence of CSF in the sinonasal cavity without the invasiveness of contrast injection. Pulse sequences performed during MRI can be designed so as to enhance the probability of detecting CSF within the sinonasal cavity. As with CT cisternography, false-negative studies may result when CSF rhinorrhea is intermittent.

Nuclear medicine studies

Radioactive isotopes can be introduced into the CSF by means of a lumbar or suboccipital puncture. Serial scanning or scintiphotography can then be used to determine the distribution of these agents.

A commonly used adjunct is the placement of nasal pledgets in various high-risk areas. These pledgets then can be analyzed for the presence of the tracer. Different tracers, including radioactive iodine-131, radioactive iodinated serum albumin (RISA), ytterbium-169, diethylenetriamine pentaacetic acid (DTPA), indium-111 DTPA, technetium-99m human serum albumin, and99m Tc pertechnetate can be used. Despite their relative safety, studies based on these tracers have several limitations, including the following:

  • Precise localization of the defect site is difficult
  • The isotope is absorbed into the circulatory system and can contaminate extracranial tissue.
  • Patient positioning can cause distal pledgets to incorrectly absorb the isotope.
  • False-positive results are present in as many as 33% patients.
  • Borderline readings are not reliable. A high reading of radioactivity is necessary to diagnose a true leak.

For further information, please see Cerebrospinal Fluid Leak Imaging in the Radiology section.

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Diagnostic Procedures

The injection of intrathecal fluorescein has been used to diagnose and localize the site(s) of cerebrospinal fluid (CSF) rhinorrhea.[7]

The injection of intrathecal fluorescein is commonly used to diagnose and localize the site(s) of CSF rhinorrhea. However, the US Food and Drug Administration has not approved the use of fluorescein for this purpose.

A lumbar puncture and/or placement of a subarachnoid lumbar drain is used to facilitate the injection. After puncture or drain placement, 10 mL of CSF is withdrawn in a sterile fashion. Precisely 0.1 mL of 10% nonophthalmic fluorescein solution is diluted in the 10 mL of CSF. The mixture is then reinjected into the subarachnoid space over a period of 10 minutes. The use of this dilution and the slow injection technique help minimize central potential complications (eg, seizures) that have been previously reported with intrathecal fluorescein.

In most instances, fluorescein is visible with standard xenon light sources used during endoscopic sinus surgery. However, minute amounts of fluorescein resulting from small bony defects may be difficulty to detect using a rigid endoscope.

Since the peak absorption of fluorescein occurs at 494 nm, a blue-light filter (440-490 nm wavelength) can help enhance visualization. This is particularly useful when fluorescein is filling an encephalocele or in cases of very small leaks that cannot be observed with standard xenon light sources. See the image below.

After intrathecal fluorescein is administered, an After intrathecal fluorescein is administered, an exposed frontal recess encephalocele is seen.
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Contributor Information and Disclosures
Author

Kevin C Welch, MD Associate Professor, Department of Otolaryngology-Head and Neck Surgery, Northwestern University, The Feinberg School of Medicine

Kevin C Welch, MD is a member of the following medical societies: American Academy of Otolaryngology-Head and Neck Surgery, American Rhinologic Society

Disclosure: Nothing to disclose.

Specialty Editor Board

Francisco Talavera, PharmD, PhD Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Received salary from Medscape for employment. for: Medscape.

Stephen G Batuello, MD Consulting Staff, Colorado ENT Specialists

Stephen G Batuello, MD is a member of the following medical societies: American Academy of Otolaryngology-Head and Neck Surgery, American Association for Physician Leadership, American Medical Association, Colorado Medical Society

Disclosure: Nothing to disclose.

Chief Editor

Arlen D Meyers, MD, MBA Professor of Otolaryngology, Dentistry, and Engineering, University of Colorado School of Medicine

Arlen D Meyers, MD, MBA is a member of the following medical societies: American Academy of Facial Plastic and Reconstructive Surgery, American Academy of Otolaryngology-Head and Neck Surgery, American Head and Neck Society

Disclosure: Serve(d) as a director, officer, partner, employee, advisor, consultant or trustee for: Cerescan;RxRevu;SymbiaAllergySolutions<br/>Received income in an amount equal to or greater than $250 from: Symbia<br/>Received from Allergy Solutions, Inc for board membership; Received honoraria from RxRevu for chief medical editor; Received salary from Medvoy for founder and president; Received consulting fee from Corvectra for senior medical advisor; Received ownership interest from Cerescan for consulting; Received consulting fee from Essiahealth for advisor; Received consulting fee from Carespan for advisor; Received consulting fee from Covidien for consulting.

Additional Contributors

Lanny Garth Close, MD Chair, Professor, Department of Otolaryngology-Head and Neck Surgery, Columbia University College of Physicians and Surgeons

Lanny Garth Close, MD is a member of the following medical societies: Alpha Omega Alpha, American Head and Neck Society, American Academy of Facial Plastic and Reconstructive Surgery, American Academy of Otolaryngology-Head and Neck Surgery, American College of Physicians, American Laryngological Association, New York Academy of Medicine

Disclosure: Nothing to disclose.

James Stankiewicz, MD Professor, Chair, Program Director, Department of Otolaryngology-Head and Neck Surgery, Loyola University Chicago School of Medicine

James Stankiewicz, MD is a member of the following medical societies: American College of Surgeons

Disclosure: Nothing to disclose.

Nadieska Caballero, MD Fellow in Rhinology and Skull Base Surgery, Sinus and Nasal Institute of Florida

Nadieska Caballero, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Otolaryngology-Head and Neck Surgery, American Medical Association, American Rhinologic Society

Disclosure: Nothing to disclose.

Acknowledgements

Joseph M Scianna, MD   Co-Director of Sinus and Sleep Disorders, Assistant Professor, Department of Otolaryngology-Head and Neck Surgery, Loyola University Medical CenterJoseph M Scianna is a member of the following medical societies: American Academy of Facial Plastic and Reconstructive Surgery, American Academy of Otolaryngology-Head and Neck Surgery, and American Rhinologic Society

Disclosure: Nothing to disclose.

Srinivas Mukkamala, MD  Staff Physician, Department of Otolaryngology-Head and Neck Surgery, Loyola University of Chicago Medical Center

Disclosure: Nothing to disclose.

 

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An axial CT of a patient with a spontaneous CSF leak reveals a defect in the posterior table of the left frontal sinus.
After intrathecal fluorescein is administered, an exposed frontal recess encephalocele is seen.
A defect in the skull base is measured with a sterile ruler.
A small cribriform plate encephalocele is observed only after removing the middle turbinate.
Septal bone is used as an underlay graft in the repair of this skull base defect in a patient with a spontaneous leak and encephalocele. (Defect measured approximately 7mm.)
Triplanar images help to identify and conceptualize the location of this lateral recess encephalocele.
This image represents an endoscopic view with a 70-degree telescope through the left frontal recess. A large defect is noted, and the meningocele has been resected. Repair of the leak can be performed with an underlay fascia graft and an anterior-based pedicled mucosa flap.
Triplanar images of a patient with a left lateral recess meningoencephalocele. The probe indicates that access to the defect is performed through the maxillary sinus and pterygopalatine fossa.
 
 
 
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