CSF otorrhea

CSF otorrhea is defined as leakage of cerebrospinal fluid (CSF) from the subarachnoid space into the middle ear cavity or mastoid air cells and then out the ear via a perforation in the tympanic membrane or defect in the external ear.

Epidemiology

There are a number of underlying causes (see below), and thus, no specific demographic is affected. 

Clinical presentation

Patients typically present with conductive deafness (due to the middle ear being fluid-filled) and a watery discharge from the ear (requiring a defect in the tympanic membrane) ¹. If the tympanic membrane is intact, fluid will discharge into the nasopharynx via the eustachian tube and may not be noticed or present with CSF rhinorrhea. Patients may also present with bacterial meningitis ¹⁰.

The diagnosis can be confirmed by identifying beta-2 transferrin in the fluid ¹⁰.

Importantly, base of skull encephaloceles with CSF leak rarely, if ever, present with signs and symptoms of intracranial hypotension ^8,9.

Pathology

Etiology

Casues of CSF otorrhea can be broadly divided into traumatic and non-traumatic causes.

Traumatic

• traumatic

  • most often due to transverse fractures of the temporal bone

• iatrogenic

  • otologic surgery

  • craniotomy involving the mastoid air cells

  • radiotherapy ¹⁰

Non-taumatic

Non-traumatic leaks can further be divided into those with no clear underlying structural cause (spontaneous) and those where some lesion or process can be identified (secondary).

• spontaneous

  • idiopathic intracranial hypertension ¹⁰

  • congenital

    • labyrinthine malformation (e.g., cochlear incomplete partition with stapes footplate deformity)

    • bony and dural defects along the temporal bone surface (especially tegmen)

    • enlargement/abnormal development of bony canals

      • facial canal ⁷

      • subarcuate (petromastoid) canal ⁶

      • Hyrtl fissure ⁵

    • ^​aberrantly distributed arachnoid granulations

• secondary

  • infection

  • mucocele ¹⁰

  • tumors

  • osteonecrosis ¹⁰

Radiographic features

CT

CT is essential in the assessment of CSF leaks as it offers unparalleled imaging on the base of skull. Thin bone-algorrythm multiplanar reconstructions should be obtained an examined for the presence of bony defects. Fluid in the middle ear cavity or mastoid air cells is also helpful.

Additionally, CT cisternography can be performed to confirm leakage of contrast into middle ear cavity or mastoid aircells.

MRI

Although MRI is unable to visualize the bony base of skull to the same extent as CT, it is excellent at demonstrating abnormal soft tissues adjacent to the defect (e.g. lesions, encephaloceles, dural thickening) as well as evidence of idiopathic intracranial hypertension if that is the underlying cause.

MR cisternography can be performed to visualize leakage of CSF into middle ear cavity or mastoid aircells ¹⁰.

Nuclear medicine

Radionuclide cisternography can be performed in complex cases although its ability to localize leaks is uncertain ¹⁰.

Treatment and prognosis

A variety of surgical options, either through the mastoid, middle ear or middle cranial fossa, are available that can be combined to maximize successful closure rates, including the use of bone wax, free muscle or facial/pericranial/bone grafts, Oxycel cotton, and fibrin glu ^11,13. These may be combined with sealing of the eustachian tube, tympanic sinus entrance and external auditory canal ¹².

Antibiotics are necessary to the treatment of infections however, although common, their use routinely in patients with base of skull fractures for prophylaxis against meningitis has not been well established ¹⁴.