Congenital anomalies of the incudostapedial joint

To describe congenital anomalies of the incudostapedial joint (ISJ) and to discuss the possible unique embryogenesis of the ISJ based on the two anomalies that were encountered.

Tertiary care medical center.

Retrospective review of the medical records of all patients with ISJ anomalies.

Four patients presented with congenital hearing loss. Upon further workup, we observed a preserved incudostapedial joint (ISJ) with deficiencies of the incus and stapes in three cases. Our fourth case demonstrated the inverse pattern of the congenital anomalies in which the ISJ was missing with an intact proximal incus and stapes crura. Three patients opted for surgical intervention with improvement in hearing. One case preferred hearing amplification over surgery.

Isolated ISJ malformations are uncommon potential causes of congenital conductive hearing loss. Although numerous patterns of ossicular anomalies have been reported in the literature, our case series is the first to demonstrate both the absence of the ISJ in one patient and the presence of the ISJ in the presence of missing stapes crura and incus body in other patients. Though limited by the small number of cases, the inverse relationship of the single case compared to the three other cases, suggests a possible independent embryological development pathway for the ISJ. Therefore, an embryological explanation of the defects should be considered. Additionally, surgical intervention can improve hearing outcomes for patients with isolated ISJ anomalies.