Blindness Due to Polymicrogyria and Asymmetrical Dilation of the Lateral Ventricles in Standard Poodles
Author(s)Van Winkle, Thomas J
Fyfe, John C
Aguirre, Gustavo D
Acland, Gregory M
Patterson, Donald F
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AbstractPolymicrogyria and asymmetric dilation of the lateral ventricles were seen in related Standard poodles that had cortical blindness. Three of the affected dogs also had gait and postural abnormalities, and one of these had seizures.Two of the affected dogs were littermates. Thorough ophthalmologic and neurologic examinations (including electroretinography, electromyography, cerebrospinal fluid analysis, plain radiographs, and computerized tomography scans) revealed no significant abnormalities outside of the brain that would account for the blindness. Computerized tomography scans in three dogs demonstrated bilateral dilation of the lateral ventricles which was more severe in the right. All dogs were necropsied between 5 and 9 months of age and had strikingly similar brain abnormalities. Numerous small irregular gyri with shallow sulci covered the middle and caudal dorsal and lateral cerebral cortex. The bony ridges of the inner calvaria in this area conformed to the underlying microgyral pattern. The lateral ventricles were asymmetrically dilated with the right more severely affected, particularly in the occipital area, and the cortical grey and white matter, including the corpus callosum, were thinned in these areas. The third and fourth ventricles and mesencephalic aqueduct were normal. Histologically, there was thinning and simplification of the cortical grey matter with an increased density of medium to large neurons. The corona radiata and subcortical white matter were also thinner than normal with no evidence of demyelination of astrocytic scarring. This congenital anomaly of the visual cortex causing blindness in the Standard Poodle appears to be inherited as an autosomal recessive trait.