Radiologic Evaluation

High-resolution computed tomography (HRCT) in the coronal and axial projections at age 6 is the radiologic study of choice. HRCT provides excellent images for the assessment of inner ear structures, mastoid pneumatization, middle ear ossicular status, patency of the oval window, course of the facial nerve, and presence of cholesteatoma. If a cholesteatoma is suspected, earlier imaging with operative intervention is warranted. HRCT is mandatory in the preoperative evaluation of the atresia patient.

Good hearing results in atresia surgery are dependent on the anatomy of the ear as documented in the HRCT. We have traditionally used three very important anatomic criteria to evaluate a patient's candidacy for surgery: (1) mastoid/middle ear pneumatization, (2) normal appearance ofinner ear structures, and (3) relationship of the facial nerve to a patent oval window and stapes footplate. With adequate pneumatization of the temporal bone, a normal inner ear, and a facial nerve in its normal course over (or perhaps slightly anterior, but always superior and posterior to) an open oval window/footplate, we have achieved excellent hearing results. Seventy-three percent of patients have achieved closure of the air-bone gap to within 30 dB.3

Jahrsdoerfer et al.8 reported an anatomic grading system to evaluate a patient's candidacy for surgery. In his system, one point is given each for patency of the oval window, middle ear space, facial nerve, malleus/incus complex, mastoid pneumati-

zation, incus-stapes connection, round window, and appearance of the external ear. Two points are given for the appearance of the stapes. Preoperative grade was predictive of postoperative hearing result, as 80% of patients with a score of > 8/10 achieved closure of the air-bone gap to within 25 dB; 72% of patients with a grade 7 achieved closure to within 25 dB, 41% of patients with grade 6, and no patient (only 3 operated on) with a grade 5 achieved closure of the air-bone gap to within 25 dB. In cases of bilateral atresia, it is not unreasonable to operate on a grade 5 patient so that some serviceable hearing may be recovered; however, in cases of unilateral atresia, we do not recommend atresiaplasty for these anatomically marginal patients, as the hearing result may not provide useful hearing.

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