Dandy-Walker malformation in a bovine Angus calf: case report and literature review.

Dandy-Walker malformation (DWM) is a rarely reported constellation of congenital cerebellar and skull abnormalities that, in humans, traditionally includes cerebellar vermis hypoplasia (or agenesis), a malformed dilated and often cystic fourth ventricle and enlargement of the posterior cranial fossa (caudal cranial fossa in veterinary species). This combination of anomalies commonly causes hydrocephalus, leading to neurological signs. DWM is thought to arise from disrupted embryogenesis of the rhombencephalic alar plate, either spontaneously or following teratogenic exposure. Secondary anomalies, such as brainstem nuclei malformations or hypoplasia, are occasionally described in association. DWM occurs infrequently in humans and has rarely been reported in veterinary species. Clinical signs commonly described in veterinary species include abnormal gait, non-progressive cerebellar ataxia, nystagmus, unilateral or bilateral absence of the menace reaction and seizures. Here, we describe a 1-day-old, 30 kg, bovine male Angus calf that was delivered by a healthy heifer and euthanized due to neurological signs. Clinically, the calf was laterally recumbent with positional nystagmus and absent palpebral reflexes. Post-mortem brain examination confirmed agenesis of the cerebellar vermis and severe dilatation of the fourth ventricle. This case report documents the gross and histopathological features of DWM in a bovine neonate and summarizes the current veterinary literature.