PERSISTENT TRUNCUS ARTERIOSUS IN A DIPROSOPIC NEWBORN CALF

A newborn diprosopic female calf had a partially duplicated head with two faces each exhibiting a mouth, a snout, an anomalous incomplete ma ndible, two eyes and a lateral ear. A single ear with two small audito ry canals was present on the midline between the two medial eyes. A ty pe 1 persistent truncus arteriosus and hypoplasia of the thoracic port ion of thymus were the most outstanding extracranial defects. In the h eart, a persistent foramen secundum and a large patent foramen ovale a llowed communication between the right and left atria. In the right ve ntricle, the small conus arteriosus was separated in part from the inf low tract by an anomalous septomarginal muscular septum'. An intervent ricular septal defect was also present. A large undivided truncus arte riosus, exhibiting a tricuspid truncal valve at its origin, arose for the most part from the conus arteriosus of the right ventricle. The tr uncus gave rise to the brachiocephalic trunk, the aortic arch, a small pulmonary trunk, from which the left and right pulmonary arteries eme rged, and two coronary arteries. The etiology and pathogenetic mechani sms implicated in the appearance of persistent truncus arteriosus are reviewed. It is suggested that a deficit or insufficiency in the crani al neural crest may play a role in the pathogenetic mechanisms leading to the production of persistent truncus arteriosus and related defect s in cephalic duplications.