Vascular mineralization (siderocalcinosis) in the brain of horses has been usually assumed to be an incidental age-related finding with no clinic significance. In the present study, eight 15-32-year-old horses of different breeds with cerebral siderocalcinosis were studied. Four of these horses had acute and severe central nervous system clinical signs of unknown etiology, 2 horses had neurological signs of known cause, and 2 horses did not have neurological signs. Gross examination of the brains in 4 animals revealed symmetrical foci of malacia in the cerebellar white matter. Histologically, moderate to severe mineralization of blood vessels and parenchyma were observed in all 8 horses, occasionally associated with necrosis of the adjacent tissue. Some horses were tested by virus isolation, polymerase chain reaction, immunohistochemistry, and serology to investigate Rabies virus; West Nile virus; Equid herpesvirus 1 and 4; Eastern, Western, Venezuelan, and Saint Louis encephalitis virus; and Sarcocystis neurona infection. These tests were negative in all samples analyzed. Brain cholinesterase activity and heavy metal screening were also unremarkable. The significance of the vascular and parenchymal mineralization in the brains of some of these horses remains undetermined. However, the severity of the lesions observed in the brains of some of the animals in the present study, coupled with the negative results for other common causes of neurological disease in horses, suggests a possible relationship between siderocalcinosis and the clinical signs observed.
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