The Antrum-Malleus-Tegmen Score: A Pilot Study Assessing Preoperative Radiographic Predictors for Transcanal Endoscopic Cholesteatoma Dissection

OBJECTIVE: Identify features on computed tomography (CT) that predict mastoidectomy conversion (MC) during transcanal endoscopic ear surgery (TEES).

STUDY DESIGN: Retrospective case-control.

SETTING: University otology practice.

PATIENTS: Consecutive patients with cholesteatoma.

INTERVENTION: TEES cholesteatoma dissection versus those requiring MC.

MAIN OUTCOME MEASURES: Antrum opacification, depth of scutum involvement, and erosion of the mastoid trabeculae, ossicular chain, and tegmen were evaluated. Univariable and multivariable regression analysis was performed. The Antrum-Malleus-Tegmen (AMT) score was created using receiver operating characteristic curves to assess feasibility of performing TEES for cholesteatoma dissection.

RESULTS: There were 39 TEES and 19 MC cases. Groups had similar age (median 28.5 yr), gender, laterality, and revision surgery status. Median surgical time for MC cases was longer than TEES (231 min vs. 171 min, p < 0.001). Radiographic predictors of MC by multivariable regression included antrum opacification (p = 0.036), malleus erosion (p = 0.044), and tegmen erosion (p = 0.023). The AMT score predicted the feasibility of TEES without MC with a sensitivity of 90% and specificity of 75% when ≥2 of the following conditions were met on preoperative CT: intact tegmen, intact malleus, and absence of antrum opacification.

CONCLUSIONS: An aerated antrum, intact malleus, and intact tegmen suggest that TEES cholesteatoma dissection without the need for mastoidectomy is highly likely. A score of ≥2 on the AMT score predicts this with a positive predictive value of 88% and negative predictive value of 78%.