Clinical aspects of temporal bone anomalies.

The term "anomaly" refers to a marked deviation from a normal standard usually caused by a hereditary or congenital defect. While there are many classifications of temporal bone anomalies, we believe that a simple division into major and minor anomalies of the temporal bone is sufficient. Major malformations (anomalies) are those in which there is stenosis or atresia of the external ear canal. The auricle is usually small and poorly formed (microtia). In minor malformations, the congenital problem is largely limited to the middle ear and frequently involves the stapes/facial nerve axis. The external ear is fairly well formed, perhaps even normal. The external ear canal is patent and a tympanic membrane can be identified. Based on experience in over 800 patients evaluated for congenital ear malformations, we have developed a practical grading scheme to rate the patient's candidacy for surgery. This rating is based primarily on the computed tomography (CT) scan, although the appearance of the external ear factors into the final score. In cases carefully selected according to this system, there is an 80% chance of restoring hearing to normal or near normal levels through surgery. This manuscript will focus on the reasons for the decision to operate and will show selected case material to illustrate the salient points.