An 18-month-old mixed breed steer had incoordination, blindness, and opisthotonos for ten days. The clinical condition progressed to lethargy and lateral recumbency, and the steer was euthanized due to poor prognosis. There is a cyst located mainly on the left side of the brain, moderately distending the third ventricle and protruding through the transverse fissure into the right dorsal thalamic region anterior to the rostral colliculi. The cyst is 3.3 x 3.5 x 3 cm, consists of a thin transparent membrane filled with translucent fluid, and has numerous slightly elongated opaque white structures of approximately 1 mm (protoscolices) adhered to the inner aspect of the capsule (Fig. 1). The cyst causes compression and atrophy of the thalamus and hippocampus, more pronounced on the left side (Fig. 2). There is dilation of the lateral ventricles, moderate on the left side and mild on the right side. The mesencephalic aqueduct is moderately distended.
