Congenital malformations of middle and inner ears of parabiotic twins.

We describe herein the congenital malformations of the middle and inner ears in temporal bones of parabiotic, monozygotic twins. Temporal bones were removed from twin B, who had no fetal cardiac activity and was born dead at 23-4/7 weeks, and twin A, the donor or "pump" twin in intrauterine life, who died shortly after birth at 20-6/7 weeks. The temporal bones were processed routinely in celoidin, stained with hematoxylin and eosin, and examined by light microscopy. We found that twin B had Mondini's dysplasia with associated deformities of the middle ear and in general showed more developmental anomalies than twin A, and we conclude that Mondini's dysplasia with anomalies of the middle ear may occur in the parabiotic twin syndrome, and the abnormalities may be explainable as the result of vascular disturbance, which also causes other lesions in these unusual cases.