Predicting Mastoid Extension and Complications such as Labyrinthine Fistula and Dural Exposure in Middle Ear Cholesteatoma Using Lesion Size and Detectability on Non-echo-planar Diffusion-weighted MR Imaging.

Purpose: This study aimed to quantitatively evaluate whether non-echoplanar diffusion-weighted MRI (non-EP DWI) lesion size and detectability can predict mastoid extension and complications such as labyrinthine fistula and dural exposure in middle ear cholesteatoma.

Methods: This retrospective study included 120 lesions with surgically confirmed middle ear cholesteatoma. Non-EP DWI was performed within 6 months preoperatively and evaluated for lesion detectability and size measurements, including maximum axial diameter, maximum axial area, and volume. Surgical findings were used to assess mastoid extension, labyrinthine fistula, and dural exposure.

Results: Of the 120 lesions, 30 were undetectable and 90 were detectable on non-EP DWI. Undetectable lesions had significantly less mastoid extension or labyrinthine fistula compared to detectable lesions (P < 0.001 - P = 0.006). The undetectable finding on non-EP DWI for identifying mastoid extension-negative lesions showed a sensitivity of 0.59, specificity of 0.95, and for labyrinthine fistula-negative lesions showed a sensitivity of 0.29, specificity of 1.00. Among the 90 detectable lesions, all size parameters (maximum axial diameter, maximum axial area, and volume) were significantly larger in cases with positive mastoid extension and positive labyrinthine fistula compared to negative cases (P < 0.001 - P = 0.005). For dural exposure, the maximum axial diameter and maximum axial area were significantly larger in positive cases (P = 0.002), but volume did not differ significantly. Optimal diagnostic cut-off values were determined for mastoid extension (8.9 mm diameter and 56 mm² area, both with sensitivity 0.89 and specificity 0.97), labyrinthine fistula (82 mm² area, sensitivity 0.47, specificity 1.00), and dural exposure (14.3 mm diameter, sensitivity 0.59, specificity 0.87; 112 mm² area, sensitivity 0.68, specificity 0.73).

Conclusion: Non-EP DWI lesion size and detectability can predict important operative findings in middle ear cholesteatoma. Undetectable lesions on non-EP DWI indicate a lack of mastoid extension or labyrinthine fistula, while larger detectable lesions correlate with increased risks of extension and complications.