Two‐headed, two‐necked conjoined twin calf with partial duplication of thoracoabdominal structures: Role of blastocyst hatching

Abstract

Gross anatomical analysis of a derodidymic monosomic stillborn male calf from an embryo transfer recipient was carried out. Two normal heads were present on two necks which were fused at the shoulders. Although the ribs were abnormal in shape and number, there was one trunk and four legs. The vertebrae were double and partially fused from the thoracic region to the sacrum, which was singular and normal. In the thoracic region there was a single vertebral canal that contained two incompletely fused spinal cords which shared common meninges. In the lumbar region there was a spina bifida. The medial neck musculature was variously fused. Two esophagi entered one enlarged rumen and the liver and gallbladder had extra lobes. Two sets of lungs occupied three pleural cavities and also part of the pericardial cavity. Two hearts were joined by a common cavernous venous sinous. The vasculature cranial to the heart reflected the doubling. The vasculature caudally was singular. The calf was uniscrotal and ipsilaterally cryptorchid. Our results are consistent with the hypothesis that atypical "hatching," that is, emergence of the blastocyst from the zona pellucida, may cause anomalous twinning.

Parapagus Conjoined Twin Calf: A Case Study - Focused on CT and Cardiac Abnormalities

“…McGirr et al. () summarized various experiments on early embryos, which are leading to conjoined twins by mechanical splitting. Furthermore, they described that two embryonic axes can result from atypical emergence of the blastocyst from the zona pellucida between days 7 and 12 of gestation, which is exactly the same time period during which the inner cell mass manifests anterioposterior polarity (Spencer, ).…”

“…The highest incidence of duplication anomalies among animals and humans (McGirr et al., ; Lanteri et al., ) occurs in ruminants. It is said to be one in 100 000 births (Vanderzon et al., ).…”

A case of a giant mass in the lumbar region of a newborn calf

“…Duplicitas occurs relatively frequently in calves, with an approximate incidence of one per 100,000 animals 11,12) . The etiology of duplicitas remains largely unclear 13) .…”

Diprosopus, craniorachischisis, arthrogryposis, and other associated anomalies in a stillborn lamb

“…Cranial duplications can be either diprosopus or dicephalus [7,16]. While diprosopus is characterized by fusion of the craniofacial structures of the two heads [5,11,13,15], partial duplication of the spine with the presence of two heads is described as dicephalus [8,10,12]. We regarded this case as diprosopus because of the fusion of the two heads at the occipital level.…”