Figure 14-85.

Leukoencephalomalacia, Brain, Horse.

A, Sagittal section. The white matter of the frontal and parietal lobes is necrotic (malacia). The gray matter is not affected. This disease is caused by the toxin fumonisin B₁ produced by the fungus Fusarium moniliforme, which grows in damaged feed grains. Note that this case demonstrates the extent and distribution of liquefactive necrosis in the white matter in this disease. A more typical presentation is shown in B. B, Transverse section. The white matter of the three cerebral gyri located at the top of the illustration has areas of yellow gelatinous softening (arrows) and hemorrhage. Because of the absence of cavitation (liquefactive necrosis), the age of this lesion is likely less than the lesion depicted in C. C, Note the severe injury of the white matter. Myelinated axons are fragmented, and myelin debris is abundant. Numerous macrophages are present in the space previously occupied by myelinated axons, and they are phagocytosing the cellular debris. H&E stain.

(A courtesy Dr. J. Simon, College of Veterinary Medicine, University of Illinois. B courtesy Dr. W. Crowell, College of Veterinary Medicine, University of Georgia; and Noah's Arkive, College of Veterinary Medicine, The University of Georgia. C courtesy Dr. W. Haschek-Hock, College of Veterinary Medicine, University of Illinois.)