CSF rhinorrhea

Last revised by Frank Gaillard on 9 Mar 2024

CSF rhinorrhea refers to a symptom of cerebrospinal fluid (CSF) leakage extracranially into the paranasal sinuses, thence into the nasal cavity, and exiting via the anterior nares. It can occur whenever there is an osseous and dural defect of the skull base that communicates directly or indirectly via paranasal or mastoid sinuses with the nasal cavity and nasopharynx.

CSF rhinorrhea presents as intermittent, often positional, discharge of clear fluid from the nose.

Additionally, the communication between the normally sterile subarachnoid space and the nasal cavity allows pathogens entry, resulting in a lifetime risk of meningitis of 19% 10.

Diagnosis is usually confirmed biochemically by detecting beta-2-transferrin in the fluid 8,10.

In the absence of trauma or surgery, idiopathic intracranial hypertension is a common and important etiology, particularly as surgical repair of these defects without treatment of the underlying cause has high recurrence rates 7.

Other etiologies include 4:

CSF rhinorrhea can occur anywhere along the base of skull that communicates either directly or indirectly, via paranasal or mastoid sinuses, with the nasal cavity and nasopharynx.

Common sites include 4:

  • cribriform plate: it is the most common site for spontaneous CSF rhinorrhea

  • sphenoid: occur at the perisellar region and the lateral recess of the sphenoid sinus, especially in the setting of idiopathic intracranial hypertension

  • temporal bone and middle ear: common sites are the tegmen tympani and tegmen mastoideum

A high resolution non-contrast CT with thin bony algorithm reconstructions in multiple planes is an essential first step in diagnostic work up of a patient with suspected CSF rhinorrhea as it enable the identification of the location of a leak in a high proportion of cases (sensitivity 88-95%) by observing the ossous defect 10. Furthermore it fascilitates planning for surgical repair.

If multiple bony defects are detected, then additional imaging is required to confirm which is responsible for the leak.

CT cisternography is useful in diagnosing an occult site of CSF leak or in determining which of multiple bony defects is responsible for the leak 4,8,10. It is performed after injecting contrast into the theca usually via a lumbar puncture and allowing it to mix throughout the CSF. This procedure is highly dependent on patient positioning and timing and requires a leak to be actively occurring during the study 10.

A leak can be confirmed by observing a streak of contrast or pooling of contrast in the anterior nasal cavity, paranasal sinus cavity and/or nasopharynx.

MRI has excellent contrast resolution without the disadvantage of ionizing radiation, however, it lacks the essential bony detail that CT can offer. As such it is usually only performed in addition to HRCT of the base of skull 10.

Heavily T2 weighted fat-saturated, preferably 3D, high-resolution sequences are capable of demonstrating a communication between the nasal cavity or paranasal sinuses and the subarachnoid space 10.

MR cisternography is similar to CT cisternography, using a small amount of intrathecal gadolinium and allowing it to diffuse throughout the CSF. High resolution 3D fat saturated T1 weighted sequences can then identify high signal intensity CSF pooling within the nasal cavity or paranasal sinuses.

Proponents of the technique cite increased sensitivity compared to CT cisternography, without ionizing radiation 10.

Important: intrathecal administration of gadolinium-containing contrast agents is considered off-label use by the US Food and Drug Administration (FDA) as there is evidence of significant neurotoxicity in higher doses 11.

Radionuclide cisternography is reserved as a problem solving investigation in cases where a leak has not been identified using HRCT and citernography. A radiotracer (technetium-99 DTPA or indium-111 DTPA) is injected into the theca and pletgets are placed in both sides of the nasal cavity and radioactivity is then measured in each to determine if they have absorbed radiotracer-contating CSF 10.

Although potentially sensitive in diagnosing the presence of a leaks, as they will detect intermittent low-flow leaks, planar images and SPECT have poor anatomic resolution.

More recently Cu-64 DOTA has been described as a PET-CT radiotracer 12.

Although historically craniotomy was performed for repeat of the anterior cranial fossa leaks, more recently endoscopic transnasal repair has become the mainstay of treatment 13.

Leakage of spinal fluid into either the nose or the ear was first described as a pathologic entity in 1899 by Sir St Clair Thomson (1859 - 1943) English laryngologist 3,9.

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