Spontaneous cerebrospinal fluid leak presenting as unilateral (left-sided) middle ear effusion.

Abstract

Spontaneous leak of cerebrospinal fluid (CSF) into the middle ear occurs rarely and can easily be missed, especially in adults. Although the presenting symptoms can be subtle, early suspicion and confirmatory imaging can establish the diagnosis. Most previously reported cases of spontaneous CSF leak into the middle ear occurred on the right side. We report a case of left-sided single-defect spontaneous leak.

Introduction

Most cerebrospinal fluid (CSF) leaks originate in traumatic, infectious, or congenital temporal bone defects. (1) However, CSF leakage can also occur without any apparent cause. Typically, the symptoms and clinical findings associated with such spontaneous CSF leaks are consistent with those of unilateral middle ear effusion. (2) Myringotomy will reveal the presence of a profuse watery fluid. Because meningitis is not uncommon in this clinical entity, prompt diagnosis and treatment are essential.

Most previously reported cases of spontaneous CSF leak into the middle ear occurred on the right side. (3-6) We report a case of a left-sided leak.

Case report

A 5 9-year-old woman with a history of recent left-sided hearing loss presented to our ENT department. She denied any history of head trauma or otologic problems. Audiometric studies revealed left-sided conductive hearing loss with a type B tympanogram. Findings on fiberoptic examination of the nasopharynx were normal.

Placement of a left-sided ventilation tube resulted in a continuous discharge of clear otorrhea. Biochemical analysis of the fluid with beta-2-transferrin identified the fluid as CSE High-resolution computed tomography (CT) of the temporal bone demonstrated an extensively pneumatized but opaque mastoid and a defect in the tegmen tympani (figure).

The patient underwent tympanomastoid exploration. The 1-cm defect in the tegmen tympani was located at the level of the lateral semicircular canal, and it extended to a level anterior to the head of the malleus. The defect was sealed with bone dust and tissue glue. A lumbar drain was inserted for 72 hours. The patient improved, and at the 3-month follow-up, the discharge had resolved and no other sign of CSF leak was evident.

Discussion

The diagnosis of CSF middle ear effusion requires a high degree of clinical suspicion. It has been recommended in the literature that any patient older than 50 years who has recurrent serous middle ear effusion should be suspected of having a CSF leak until proved otherwise. (7) Spontaneous temporal bone CSF leaks can involve both the middle and posterior fossa plates, but the vast majority involve the tegmen tympani. (3,8)

The pathophysiology of CSF leak into the middle ear is not entirely understood. Two theories have been proffered to explain nontraumatic defects in the tegmen of the temporal bone: the congenital defect theory (7) and the arachnoid granulation theory (3,9,10):

* According to the congenital origin theory, bony pathways that are present at birth--either a widely patent cochlear aqueduct, a tympanomeningeal fissure, or an internal auditory canal communication with the vestibule--can persist after birth and serve as routes for pathogens to enter the CSF space, causing meningitis in children.

* According to the other theory, arachnoid granulations that do not get a venous drain during embryonic development come to lie in a blind end against the inner bony surface of the skull. The central portion of an arachnoid granulation contains CSF; the CSF is covered by arachnoid cells that are loosely attached to a fibrous capsule that is covered by endothelium. In patients with spontaneous CSF leaks, the arachnoid granulations are covered only by a thin fibrous capsule. It is thought that arachnoid granulations become aberrantly located close to temporal bone dura. With time, the pressure of CSF from the subarachnoid space supposedly causes erosion through the fibrous covering of the arachnoid granulation. Pulsations of CSF from the subarachnoid space result in further erosion through the floor of the anterior, middle, or posterior cranial fossa, thus resulting in a CSF leak.

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The predisposition of spontaneous leaks to occur on the right side has been attributed to the fight-sided dominance in the venous outflow of the brain. (4) This dominance is presumably the result of the lower pressure in the right jugular bulb, which occurs as a result of both a gravitational effect and the direct suction action from the right cardiac atrium during diastole.

The beta-2-transferrin assay is highly sensitive and specific for CSE Only a small amount of CSF is required for this test. Another reliable method of identifying CSF is glucose testing with a multireagent strip; fluid is more likely to be CSF when the glucose content is lower than corresponding serum values but higher than glucose measurements in nasal mucus or lacrimal secretions. However, active meningitis can lower CSF glucose concentrations and thus confound the results of quantitative glucose analysis, resulting in a false negative. High-resolution CT is the imaging modality of choice for identifying a CSF leak. (11)

Surgical repair is recommended, regardless of the patient's age. There are two main approaches: transmastoid and middle cranial fossa. (7) The transmastoid approach has the advantage of allowing for assessment of the middle and posterior fossa plates while avoiding the need for a craniotomy and temporal lobe retraction; it is useful for smaller (<2 cm) single defects. The middle cranial fossa approach (alone or in combination with a transmastoid approach), provides wide exposure of the floor of the middle cranial fossa so that multiple defects, if present, can be identified and repaired.

In conclusion, spontaneous CSF leak caused by a tegmen defect in adults can occur without any history of head trauma, temporal bone fracture, or meningitis. When an adult presents with aural fullness and persistent fluid in the middle ear, CSF leak should be suspected, especially if the patient does not have a recent history of upper respiratory infection, ear pain, trauma, or a nasopharyngeal mass. The diagnosis should also be suspected when an adult reports persistent watery or slightly yellow-tinged otorrhea after placement of a ventilation tube.

References

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(10.) Gacek RR. Evaluation and management of temporal bone arachnoid granulations. Arch Otolaryngol Head Neck Surg 1992;118(3): 327-32.

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Kavadi T. Rajkumar, MBBS, DLO; Ahmed A. Orabi, FRCS, MSc; Michael S. Timms, FRCS

From the Department of Otorhinolaryngology, Blackburn Royal Infirmary, Blackburn, U.K.

Corresponding author: Dr. Kavadi T. Rajkumar, Department of Otorhinolaryngology, Royal Infirmary, Blackburn BB2 3LP, UK. Phone: [phone]; fax: [phone]; e-mail: [e-mail]