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A case of barotrauma-induced pneumolabyrinth secondary to perilymphatic fistula.


We report the case of a 62-year-old woman who experienced pneumolabyrinth associated with a perilymphatic fistula. Her condition was diagnosed with the help of computed tomography; which detected the presence of an air bubble in the labyrinth, and middle ear exploration, which revealed that clear fluid was emanating from the round window niche in a manner consistent with the presence of a perilymphatic fistula. The niche was repaired with tragal perichondrium and bolstered with Gelfoam.


Perilymphatic fistula still remains a controversial topic in the otologic literature. Pneumolabyrinth associated with a perilymphatic fistula is rare. When it does occur, it is usually identified on high-resolution computed tomography (CT) of the temporal bone. Mafee et al were among the first to describe such a finding, which they observed in a patient with a fracture of the stapes footplate. [1]

Pneumolabyrinth resulting from perilymphatic fistula has also been associated with barotrauma, iatrogenic injury, head trauma, and chronic ear disease; it can also develop spontaneously. Potential sites of gas entry include the oval and round window niche, microfissures between the posterior semicircular canal and the round window, and the fissula ante fenestram. [2] In this article, we report a case of pneumolabyrinth secondary to perilymphatic fistula, which was verified on surgical exploration.

Case report

A 62-year-old white woman was returning from a vacation in Mexico when she experienced an acute onset of severe vertigo with nausea and vomiting. The episode occurred after she rode down a small mountain in a car.

The next day, she visited a local otolaryngologist. The woman denied a history of head trauma or vertigo during Valsalva's maneuver. She had no antecedent illness or history of ear disease. She reported that she had experienced a similar event approximately 20 years earlier, which resulted in a sudden sensorineural hearing loss with vertigo. At that time she had been prescribed bed rest, and the vertigo eventually resolved, although her hearing never returned to normal.

On physical examination, she had normal tympanic membranes bilaterally and no evidence of any abnormality in the middle ear space. A fistula test was performed and was negative. The results of the rest of her physical examination were within normal limits. Her audiogram demonstrated a profound sensorineural hearing loss on the right and normal pure tones on the left. CT was ordered; electronystagmography was not.

CT revealed a hypodense region in the labyrinth in the right that was consistent with the presence of air (figure). Middle ear exploration revealed that clear fluid was emanating from the round window niche in a manner consistent with the presence of a perilymphatic fistula. This was repaired with tragal perichondrium and bolstered with Gelfoam.


Perilymphatic fistula has been an enigma for some time. Many theories have been offered to account for its development. Goodhill was the first to propose implosive and explosive forces as potential causes. [3] He defined implosive forces as those that cause pressure changes in the middle ear space and thus exert an external force on the oval and round window membranes, the fissula ante fenestram, the microfissures, and Hyrtl's fissure. These forces can be triggered by barometric pressure changes, compression trauma of the ear, Valsalva's maneuver, and pinched-nose sneezing. Goodhill defined explosive forces as those that exert an internal pressure by increasing cerebrospinal fluid pressure. CSF pressure is transmitted to the inner ear through a patent cochlear aqueduct and lamina cribrosa of the internal auditory canal. [4] These forces can be brought on by lifting, straining, coughing, and sneezing. Once a connection has been made between the inner ear and the middle ear cleft or the mastoid space, with its associated loss of perilymph, a relative endolymphatic hydrops develops, along with its constellation of symptoms. [5]

Animal studies have been conducted in an attempt to clarify the pathophysiology involved, but they have thus far yielded conflicting results. Bohmer was unable to detect any changes in auditory thresholds in the guinea pig after simple perforation of the round window. [6] However, Robertson was able to demonstrate changes in the tuning curves of single spiral ganglion cells in the guinea pig basilar membrane after removal of perilymph. [7]

The diagnostic workup is relatively nonspecific. Audiologic tests reported in the literature include audiography, electronystagmography, the auditory brainstem response test, and occasionally electrocochleography. [8-11] Although these tests are rarely suggestive, they do give insight into the diagnosis. Radiologic studies include plain films and high-resolution temporal bone CT. In cases of possible perilymphatic fistula, CT occasionally provides insight into the possible anatomic defect and offers supportive data toward the diagnosis.

In our patient, the high-resolution temporal bone CT taken in the axial plane demonstrated an air bubble trapped in the anterior portion of the vestibule. The horizontal canal was visible in this section, and it appeared to be normal. The coronal plane CT was taken at the level of the oval window, and it showed air in the superior portion of the vestibule. The oval window appeared to be anatomically normal, as did the basal turn of the cochlea and the internal auditory canal. The tympanic segment of the facial nerve could be seen just above the oval window.

In summary, perilymphatic fistula associated with barotrauma is a real entity. Pullen found perilymphatic fistulae in 48 of 62 patients who experienced barotrauma after scuba diving. [12] Most of these were found at the round window membrane. Pneumolabyrinth is a rare finding on high-resolution CT. Its detection supports the diagnosis of a perilymphatic fistula, with a connection between the inner ear and the middle ear cleft or mastoid. Its underlying pathophysiology is still not widely understood.

Multiple management options are available. They include simple options such as bed rest, head elevation, a stool softener, and avoidance of Valsalva's maneuver and straining. Surgical exploration is considered to be the gold standard by some. Early intervention leads to a more rapid resolution of vestibular symptoms and preservation of existing auditory function. Delayed ([greater than]2 wk) closure of perilymphatic fistula increases the possibility of permanent auditory loss. [12]


(1.) Mafee MF, valvassori GE, Kumar A, et al. Pneumolabyrinth: A new radiologic sign for fracture of the stapes footplate. Am J Otol 1984;5:374-5.

(2.) Meyerhoff WL, Marple BF. Perilymphatic fistula. Otolaryngol Clin North Am 1994:27:411-26.

(3.) Goodhill V. Sudden deafness and round window rupture. Laryngoscope 1971;81:1462-74.

(4.) Glasscock ME. The stapes gusher. Arch Otolaryngol 1973;98:82-91.

(5.) Allen GW. Clinical implications of experiments on alteration of the labyrinthine fluid pressures. Otolaryngol Clin North Am 1983;16:3-19.

(6.) Bohmer A. On the pathomechanism of cochlear dysfunction in experimental perilymph fistulas. Laryngoscope 1991;101:1307-12.

(7.) Robertson D. Cochlear neurons: Frequency selectivity altered by perilymph removal. Science 1974;186:153-5.

(8.) Healy GB, Strong MS, Sampogna D. Ataxia, vertigo and hearing loss. A result of rupture of inner ear windows. Arch Otalaryngol 1974; 100:130-5.

(9.) Fee GA. Traumatic perilymphatic fistulas. Arch Otolaryngol 1968;88: 477-80.

(10.) Arenberg IK Ackley RS, Ferraro J, Muchnik C. EcoG results in perilymphatic fistula: Clinical and experimental studies. Otolaryngol Head Neck Surg 1988;99:435-43.

(11.) Pulec JL. Perilymph fistula. Laryngoscope 1969;79:868-86.

(12.) Pullen FW. Perilymphatic fistula induced by barotrauma. Am J Otol 1992;13:270-2.
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Author:Dornhoffer, John L.
Publication:Ear, Nose and Throat Journal
Geographic Code:1USA
Date:Jun 1, 2000
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