EFFICACY OF 3D FLAIR MRI FINDINGS IN EVALUATING CHOLESTEATOMA WITH LABYRINTHINE FISTULAE

Michihiko Sone, Tadao Yoshida, Tsutomu Nakashima

Department of Otorhinolaryngology, Nagoya University Graduate School of Medicine, Nagoya, Japan

Introduction

Surgical management of cholesteatomas with labyrinthine fistulae has been reported and several treatment techniques have been advocated. These issues may have arisen as a result of selection bias in the reported techniques: there is neither a widely-used staging system for fistulae1 nor any uniform surgical technique that can be adopted for all cases.2 Computed tomography (CT) examinations are often conducted for preoperative evaluation for middle ear surgery. Additionally, diffusion-weighted magnetic resonance imaging (MRI) has been shown to be useful for the detection of cholesteatomas.3 Three-dimensional (3D)- Fluid-attenuated inversion recovery (FLAIR) MRI can aid in identification of labyrinthitis4 or with cholesteatoma and labyrinthine fistula.5

We have evaluated pre-operative 3D FLAIR MRI findings in relation to clinical features in cases of middle-ear cholesteatoma with a labyrinthine fistula, and to evaluate the suitability of MRI findings regarding fistula status and surgical management.

Materials and methods

Twenty-eight patients who underwent surgery for middle-ar cholesteatoma with one or more labyrinthine fistulae confirmed by CT were studied. Pre-operative imaging analysis was performed using 3D-FLAIR MRI before and after intravenous administration of a single dose of gadolinium. Fistula size measured by CT and the signal intensity (SI) in the affected lesion in the inner ear after contrast enhancement were evaluated with respect to the clinical features and surgical findings. SI was measured in each affected ear and in the cerebellum in the most artifact-free area, and The SI ratio (SIR) between the affected lesion and the cerebellum was then estimated.

Clinical features included hearing threshold of pre-operative bone conduction, and existence of fistula symptoms or active infection. Fistula status was classified into one of the following three stages: (I) no involvement of the endosteal membrane; (II) cholesteatoma matrix invading the endosteal membrane, so that removal of matrix would open the perilymphatic space; or (III) direct attachment or invasion of the cholesteatoma matrix or granulation tissue within the membranous labyrinth.

Results

Example image of CT and 3D-FLAIR MRI in a case with a labyrinthine fistula in the lateral semicircular canal are shown in Figure 1. There was no correlation between fistula size and the SIR. The hearing threshold determined by pre-operative bone conduction correlated with the SIR, especially in patients with acute sensorineural hearing loss, but it did not correlate with fistula size. Patients with fistula symptoms had a significantly higher SIR than those without symptoms (Table 1), and similar findings were observed in patients with an active infection. Patients with a larger fistula or higher SIR tended to have a deeper fistula and a more adhesive fistula matrix at operation (Table 2).

image

Fig. 1. Example images of CT (A) and 3D-FLAIR MRI (B) in a case with a labyrinthine fistula in the lateral semicircular canal. High signals in the lateral semicircular canal (arrowhead in B) and in the cochlea (arrow in B) of the affected ear.

Table 1. Fistula sizes and SIRs in the fistula lesion of patients with and without fistula symptoms or active infection

image

Table 2. Relationship between fistula stages, fistul

image

Discussion

Removal of the matrix at initial surgery has been proposed for patients with small fistulae.6 In the present study, sizes of fistulae detected by CT images did not related to SIRs, and the stronger signals were observed for the smaller fistulae. Thus, severe labyrinthitis can occur even in patients with a small fistula, and 3D-FLAIR images can help evaluate the severity of intra-labyrinth disturbances. Removal of the cholesteatoma might be more successful when the ear is not actively infected. 6,7 In other words, removal of the cholesteatoma matrix should be considered carefully when there is active inflammation, as this can accelerate the erosion of labyrinthine bone, and such inflammation within the inner ear could be observed on 3D-FLAIR images in the present study.

Higher elevations of hearing threshold were observed in patients with stronger SIRs, including those with preoperative acute SNHL. The prevalence of fistula symptoms was higher in those with stronger SIRs. This finding suggests that 3D-FLAIR signal represents the degree of labyrinthitis that can cause dysequilibrium.

We removed the cholesteatoma matrix at initial surgery in patients with relatively little adhesion of the matrix to the membranous labyrinth, which related to SIR. Removal of the matrix led to opening of the peri-lymphatic space in some cases with relatively weaker SIR, however, postoperative clinical symptoms including vertigo were observed less in these patients. New bone formation in the fistula site was frequently observed post-operatively in patients with relatively strong SIR, which indicated more severe inflammation in the lesions. Our impression is that 3D-FLAIR evaluation was beneficial for surgical management, especially in patients with large fistulae or symptoms related to inner ear disturbances.

Conclusion

SIR was more strongly correlated than CT findings to the clinical status of patients with labyrinthine fistulae caused by cholesteatoma. Adhesion of the cholesteatoma matrix to the membranous labyrinth correlated with the SIR. Information provided by 3D-FLAIR image is valuable in pre-operative evaluation of the status of labyrinthine fistulae caused by cholesteatoma and a useful indicator of fistulae stage and surgical management.

References

1.Copeland BJ, Buchman CA. Management of labyrinthine fistulae in chronic ear surgery. Am J Otolaryngol 24:51–60, 2003

2.Kobayashi T, Sato T, Toshima M, Ishidoya M, Suetake M, Takasaka T. Treatment of labyrinthine fistula with interruption of the semicircular canals. Arch Otolaryngol Head Neck Surg 121:469–475, 1995

3.Fitzek C, Mewes T, Fitzek S, et al. Diffusion-weighted MRI of cholesteatomas of the petrous bone. J Magn Reson Imaging 15:636–641, 2002

4.Sone M, Mizuno T, Naganawa S, Nakashima T. Imaging analysis in cases with inflammation-induced sensorineural hearing loss. Acta Otolaryngol 129:239–243, 2009

5.Sone M, Mizuno T, Sugiura M, Naganawa S, Nakashima T. Three-dimensional fluid-attenuated inversion recovery magnetic resonance imaging investigation of inner ear disturbances in cases of middle ear cholesteatoma with labyrinthine fistula. Otol Neurotol 28:1029–1033, 2007

6.Sheehy JL, Brackmann DE. Cholesteatoma surgery: management of the labyrinthine fistula-a report of 97 cases. Laryngoscope 89:78–87, 1979

7.Herzog JA, Smith PG, Kletzker GR, Maxwell KS. Management of labyrinthine fistulae secondary to cholesteatoma. Am J Otol 17:410–415, 1996


Address for correspondence: Michihiko Sone, MD, Department of Otorhinolaryngology, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya 466- 8550, Japan.

Cholesteatoma and Ear Surgery – An Update, pp. 107–109

Edited by Haruo Takahashi

2013 © Kugler Publications, Amsterdam, The Netherlands