[Preoperative evaluation of translabyrinthine cholesteatomas by MRI]

Hearing preservation is one of the major goals of surgical resection of invasive cholesteatomas. Patients were prospectively evaluated using a 3D-CISS MR acquisition in order to improve the detection of perilymphatic fistulae.

16 patients (10 M, 6 F) presenting with a primary (1 case) or a secondary (post-otitis) middle ear cholesteatoma extending to the osseous labyrinth (as defined by HR-CT) were evaluated at MR (1.5 T Vision, Siemens). The 3D-CISS sequence (TR: 12.25 ms, TE: 5.90 ms, flip angle: 70 degrees, slice thickness: 1 mm, matrix: 307 x 512, FOV: 200) allowed detection of invasion of the membranous labyrinth using a 3 level grading scale: 1) normal fluids, 2) focal and 3) diffuse obliteration of labyrinthine fluid.

While CT showed a definite osseous labyrinthine fistula, the 3D-CISS sequence depicted either a normal membranous labyrinth (9 cases), a focal obliteration of the basal turn (1 case) or lateral semi-circular canal (3 cases) or a diffuse obliteration of the labyrinthine fluid (3 cases). Diffuse obliteration of the labyrinth fluid and 1 out 3 cases of focal obliteration of the semi-circular canal were found to have perilymphatic fistulae at surgery. None of the normal labyrinths were associated with perilymphatic fistula formation.

The 3D-CISS sequence allows a comprehensive preoperative evaluation of the membranous labyrinth. Loss of signal from the labyrinthine fluid due to invasion or compression of the membranous structures accounts for the lack of specificity of the technique.