Irregular Contour of Inner Ear Structures and Hypomineralized Areas at Otic Capsule: Are They Other Additional Imaging Findings of Incomplete Partition-III?

PURPOSE: Incomplete partition III (IP-III) characterized by congenital mixed or sensorineural hearing loss is a rare genetic disease transmitted through X-linked inheritance. Incomplete partition III can be easily achieved based on pathognomonic computed tomography findings. The aims of this study were to investigate the otic capsule abnormalities in IP-III and to report irregular contour of membranous labyrinth and hypomineralized areas at otic capsule, which have not previously been described.

MATERIALS AND

METHODS

The otic capsule features of 10 subjects (8 affected patients, 1 of whom is a female; 2 carrier mothers), who were diagnosed on clinical and typical radiologic findings, were analyzed.

RESULTS

All patients had typical IP-III as described in the literature. Seven of 10 patients had irregular contour. Seven of 10 patients demonstrated hypomineralized areas, which were very hypodense to normally develop otic capsule areas. One affected patients and 2 carrier mothers had a normal-looking membranous labyrinth contour and normal mineralization at otic capsule.

CONCLUSIONS

We report for the first time the irregular contour of inner ear structures and hypodense otic capsule areas in patients with IP-III. We think that though speculative, abnormal development of the inner endosteal layer results in irregular contour of inner ear structures. Hypomineralized areas at otic capsule could be explained by abnormal development of middle enchondral layer due to reduced or absent vascular supply from middle ear mucosa during fetal life. These findings may be accepted as additional criteria of IP-III.