This disease is caused by retention of edematous fluid in the cerebral ventricles during the fetal period and is frequently observed in cattle and horse. The cerebral ventricles gradually dilate, and the brain parenchyma becomes thinner. Since many cranial sutures become separated, the head is very large compared with the face, and the skull is round. This causes difficulties in delivery. Hydrocephalus is considered to occur secondary to hypoplasia of the cerebral ventricles in the parturient canal, or due to impaired excretion of cerebrospinal fluid caused by choroid plexus inflammation in the early fetal stage. (register No. 0607)

Masanobu Goryo
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Department of Veterinary Pathology, Faculty of Agriculture, Iwate University., Morioka, 020-8550, Japan