Air in the vestibule: computed tomography scan finding in traumatic perilymph fistula

Cross Sectional Imaging of the Ear and Temporal Bone

CT and MR imaging are essential cross-sectional imaging modalities for assessment of temporal bone anatomy and pathology. The choice of CT versus MR depends on the structures and the disease processes that require assessment, delineation, and characterization. A thorough knowledge of the two imaging modalities' capabilities and of temporal bone anatomy greatly facilitates imaging interpretation of pathologic conditions.

Imaging Review of the Temporal Bone: Part II. Traumatic, Postoperative, and Noninflammatory Nonneoplastic Conditions

The first part of this review of the temporal bone discussed anatomy of the temporal bone as well as inflammatory and neoplastic processes in the temporal bone region (1). This second part will first discuss trauma to the temporal bone and posttraumatic complications. The indications for common surgical procedures performed in the temporal bone and their postoperative imaging appearance are then presented. Finally, a few noninflammatory nonneoplastic entities involving the temporal bone are reviewed. They are relatively uncommon diagnoses compared with infectious or inflammatory diseases. However, because patients present with symptoms that are either common (hearing loss) or distinctive (sensorineural hearing loss in a child), they are important for the radiologist to be aware of and recognize.

Results of Exploratory Tympanotomy following Sudden Unilateral Deafness and its Effects on Hearing Restoration

In cases of acute unilateral deafness, no consensus exists as to whether tympanotomy and sealing of the round window should be performed routinely. To further address this issue, we conducted a retrospective study of pre-, intra-, and postoperative findings in 97 patients who had undergone exploratory tympanotomy (EXT) after the onset of sudden and severe unilateral deafness. Our goal was to ascertain, if we could, whether the benefits of EXT outweigh the risks. We also took into account the effects of perilymph fistula (PLF) on the etiology of sudden hearing loss and postoperative outcomes. We found that routine EXT was indeed beneficial for these patients. It was associated with a very low surgical complication rate, and its effects on hearing as assessed by objective measures were beneficial. The greatest benefits were seen in patients who underwent EXT within 7 days after the onset of their hearing loss. With respect to PLF, we found that the presence or absence of the “typical history” of PLF (i.e., a sudden unilateral hearing loss within 48 hours after a precipitating trauma or physical exertion) had no bearing on whether a PLF was actually present in our group; nor was vertigo a reliable predictor of PLF. We recommend that EXT be performed on all patients with new-onset acute unilateral deafness, barring any contraindications, of course. The absence of a typical history of PLF should not dissuade the surgeon from proceeding with EXT.

Intraoperative assessment of perilymphatic fistulas with intrathecal administration of fluorescein

OBJECTIVES

Assessment of perilymphatic fistulas remains a diagnostic problem. Because of a lack of reliable clinical tests, exploratory tympanotomy is necessary to detect membrane leaks in the middle ear. To improve objectivity in the intraoperative visualization of perilymphatic fistulas, we used intrathecal fluorescein for perilymph staining to increase the sensitivity and specificity of diagnosis of perilymphatic fistulas.

STUDY DESIGN

Prospective study in the setting of a tertiary, referral, and academic center.

METHODS

Twenty-eight patients with suspected traumatic, idiopathic, iatrogenic, or inflammatory perilymphatic fistulas were admitted for exploratory tympanoendoscopy for perilymphatic fistula detection. Twenty-five to 100 mg sodium fluorescein 10%, diluted with cerebrospinal fluid, was administered by lumbar puncture 2.5 to 23.5 hours before tympanoendoscopy. The oval and round window niches were microscopically and endoscopically observed with white and blue light, using specific filters.

RESULTS

In two patients (7%), obvious fluorescence was detected behind the round window membrane with blue light. Direct observation of perilymph in stapedectomy and in semicircular canal fistula revealed no staining. Neurological complications of intrathecal fluorescein, as reported by other authors, were not observed.

CONCLUSIONS

Probably because of a different patency of the cochlear aqueduct, intrathecal fluorescein for intraoperative detection of perilymphatic fistula resulted in a significant perilymph staining in only a few patients. Considering the possible complications of this method, we would not recommend it for routine evaluation of perilymphatic fistula.