Aging of bovine spinal cord: an alteration of myelinated nerve fibers in the white matter

To gain more knowledge of age-related changes in the spinal cord of the bovine species, the structure of 15 clinically normal aged cattle (Holstein-Friesian cows 8–13 years of age) was histopathologically examined. In 12 (80%) of the 15 animals, the common histopathological features identified were alteration of a small number of myelinated nerve fibers in the white matter, with less than 4 nerve fibers affected per cross-sectional area of the spinal cord. Alteration of nerve fibers was characterized by dilation of myelin sheaths with loss of axons or macrophage infiltration, resembling features of Wallerian axonal degeneration. The occurrence of this nerve fiber alteration had a predilection for the lateral and ventral white matter funiculi. In eight cattle, so-called axonal spheroids were rarely present in the white matter. There was little evidence of glial reaction against nerve fiber alteration. Gray horn neurons were unremarkable. Lipofuscin granules were recognized in neurons, glial cells, and neuropil of the medulla oblongata examined in six cows. The changes observed in the spinal cord white matter of the present cows were similar to those described previously in aged human beings and domestic and laboratory animals, and thus were likely to have been a phenomenon which was closely related to aging. The strict clinical significance of the histopathological changes in the spinal cord white matter remains undetermined.