Cranioschisis, also known as cranial dysraphism, is a congenital genetic defect which is seen as fissure in skull bones. The bony midline cranial defect allows formation of a cephalocele, which is the congenital herniation of intracranial contents in which the meninges or brain protrudes via a scalp defect. The skull sutures of the newborn puppy can only be felt by careful examination. Failure of sutures to close appears as "soft spots." The soft crevices can be about 1/8 inch wide and 1/4 inch long. Instead of disappearing, they become wider. The condition is lethal.
Cranioschisis can result from high concentrations of retinoids which occur in some pet food formulations as a result of the use of animal liver as an ingredient. A study of the teratogenic (causing birth defects) potential of dietary vitamin A in cats investigated the incidence of birth defects in kittens of queens given diets with retinyl acetate concentrations of 6000, 306000, or 606000 retinol equivalents (RE)/kg diet for approximately 3 years. Malformations in newborn kittens included cleft palate, cranioschisis, enlarged heart, poor development of the spinal cord and small intestine, which are typical fetal defects consistent with ingestion of excess retinoids in other species.
- Roy Robinson. Genetics for Dog Breeders
- T. L. Freytag , S. M. Liu, Q. R. Rogers, and J. G. Morris. Teratogenic effects of chronic ingestion of high levels of vitamin A in cats