Hearing levels in patients with microtia: correlation with temporal bone malformation.

Objective: To evaluate the relationship between hearing level and temporal bone abnormalities in patients with microtia.

Study Design: Retrospective case series study between 1992 and 2004.

Setting: Academic, tertiary care referral medical center.

Patients: We evaluated 115 ears of 89 patients (68 males, 21 females; mean age, 11 yr; range, 5-44 yr) with microtia.

Main Outcome Measures: Hearing level was examined in patients with microtia. Developmental abnormalities of the temporal bone were evaluated by Jahrsdoerfer's computed tomography (CT) scoring system using high-resolution CT (HRCT) scans of the temporal bone. Temporal bone malformation scores were divided into four subgroups: ossicular development, windows connected to the cochlea, aeration of the middle ear cavity, and facial nerve aberration. Patients were divided into the stenosis and atresia groups on the basis of the appearance of the external auditory canal (EAC). We also evaluated the relationships between hearing level and four subtotal scores of the HRCT findings in the stenosis and atresia groups.

Results: There was no relationship between hearing level and total points of HRCT scoring system or between hearing level and severity of microtia scored by Marx classification. With regard to subtotal points related to ossicles (4 points), the hearing level in ears with low scores (<2) (64.7 +/- 1.6 dB) was significantly different (P = .03) from that in ears with high scores (> or =2) (54.0 +/- 2.8 dB) in the stenosis group. In the atresia group, the hearing level was 64.3 +/- 2.2 dB in ears with low scores and 62.3 +/- 1.1 in ears with high scores (P > .5). As for subtotal points related to the windows connected to cochlea (2 points), the hearing level was 64.8 +/- 2.6 dB in ears with low scores (0) and 55.9 +/- 2.4 dB in ears with high scores (> = 1) in the stenosis group. In the atresia group, the hearing level was 67.7 +/- 2.3 dB in ears with low scores and 61.5 +/- 1.0 in ears with high scores. There was significant difference between ears with low and high scores in the stenosis group (P = .03) and atresia group (P = .009). There was no significant difference between ears with low and high scores with respect to the subtotal points related to aeration of the middle ear cavity and aberration of the facial nerve.

Conclusion: The hearing level in microtic ears correlated with the formation of oval/round windows and ossicular development but not with the degree of middle ear aeration, facial nerve aberration, or severity of microtia. The hearing level can also serve as an indictor, such as the HRCT findings, to determine whether a subject's hearing will likely improve after reconstructive surgery.