Diprosopia/dicephalia in calves in Northern Italy: clinical and aetio-pathological features

Cephalic parapagia, a rare congenital anomaly caused by the fusion of two monozygotic embryos, is characterized by a single body and a spectrum of duplication of craniofacial structures. The authors describe the clinical and pathological aspects of the parapagus conjoined twin defect in nine calves referred to the Department of Animal Pathology, Turin, between 1999 and 2009. The majority of the calves (eight cases) presented two snouts that shared three or four eyes (diprosopia); one calf presented two separate skulls fused at the foramen magnum (dicephalia). Bilateral inferior brachygnathia was observed in four calves. Post-mortem examination of the skull revealed complete brain duplication with fusion at the caudal portion of the brainstem in all calves. Histological features of the cerebral hemispheres and brainstem were normal; moderate disorganization of the cerebellar cortex was noted in two cases. Cardiac malformations were observed in three calves. No aetiologic cause was determined. This article underscores the importance of diprosopia in cattle species and suggests the need for more detailed investigations to better understand its pathogenesis.