FP02-2. CONDUCTIVE DEAFNESS WITH NORMAL EARDRUM: ABSENCE OF LONG PROCESS OF THE INCUS

Keehyun Park, Yun-Hoon Choung, You Ree Shin, Sung Pyo Hong (Ajou University School of Medicine, Suwon, Korea)

Objectives: A non-progressive and conductive hearing loss with normal eardrum which has no history of trauma and infection, is highly suggestive of a congenital ossicular malformation. Among ossicular anomalies, absence of long process of the incus has been sometimes suggested. However, there is a suggestion that this kind of pathology may be due to acute otitis media to which the patients succumbed in their infancy or childhood. This conductive hearing loss with normal eardrum is due to resorption of long process of the incus by its potential inflammation. The purpose of this study is to clarify whether the absence of long process of the incus is caused by inflammation or anomaly.

Methods: We experienced 7 cases (4 bilateral cases, 3 unilateral cases) of absence of long process of the incus which were confirmed through explotympanotomy at Ajou University Hospital for the last 10 years. Temporal bone CT, operative and histopathologic findings were analyzed. We also demonstrated 3D reconstructive image and volume fraction of pathologic incuses through 3D micro-CT.

Results: 2 bilateral cases showed fibrous changes of long process of the incus instead of its complete absence. All unilateral cases showed resoprtive evidence by inflammation on light micrograph and volume fraction of 3D micro-CT of the incus. In temporal bone CT, 1 out of 3 unilateral cases showed relatively decreased pneumatization of the temporal bone of the diseased side in comparision with that of the healthy side.

Conclusions: The most likely causes of the lesion of long process of the incus had a possibility of a potential inflammation. However, we could not completely exclude a possibility of congenital anomaly of this lesion.

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