Interstellar encounter: Postmortem imaging and virtopsy on a preserved anencephalic Indo-Pacific bottlenose dolphin specimen after 30 years

Abstract

Background

Anencephaly is a deadly type of cephalic axial skeletal and neural disorder with a multifactorial aetiology that causes the failure of the rostral neuropore closure, compromising the formation of the neural folds, basicranium, and neurocranium. In cetaceans, there is only one report of this fetal abnormality, dated in late 1991, in a male stillborn Indo-Pacific bottlenose dolphin (Tursiops aduncus) and diagnosed using transabdominal ultrasonography on its mother that was kept under human care in the Ocean Park Corporation. After birth, physical and general radiographic examination showed kyphosis of the cervical and lordosis of the thoracic vertebrae, narrowed triangular skull base, thickening of an undersized maxilla, cranial vault defect including the absence of the bones constituting the roof of the cranial cavity. The stillborn was then fixed in formalin for future research.

Case presentation

The preserved dolphin specimen was further investigated using different advanced radiological and imaging techniques postmortem, including 3D surface scanning (3DSS), computed tomography (CT), and magnetic resonance imaging (MRI). The scans were then used to conduct virtual necropsy (virtopsy) for detailed gross morphological analyses of the malformation. CT confirmed the total absence of the interparietal bone but also revealed the presence of greatly reduced other bones. The reduction of the parietal and occipital bone resulted in a large cranial vault defect instead of the interfrontal and fronto-occipital sutures. MRI showed the remaining of the optic and vestibulocochlear nerve which suggests the condition of human meroanencephaly.

Conclusions

In summary, this study reported the importance of the use of advanced radiological and imaging tools in rare and complex malformations such as anencephaly in a stillborn cetacean. Although the malformation was diagnosed using prenatal transabdominal ultrasonography, it was later confirmed revealing new insights using virtopsy. Although ultrasound is an established method to monitor pregnancy, fetal growth and wellbeing, virtopsy provided a more accurate characterization of the bone and neural malformations postmortem. This example highlighted the importance of using virtopsy as a postmortem technique to understand the nature and characteristics of pathologies in cetaceans.