Abstract
Degenerative myelopathy and vitamin A deficiency were diagnosed in a 1-year-old, female, black-maned lion (Panthera leo). Diffuse white matter degeneration characterized by dilated myelin sheaths, Wallerian degeneration, and reactive astrocytosis was present at all levels of the spinal cord. With luxol fast blue–cresyl echt violet stain, bilaterally symmetrical demyelination was observed in the fasciculus cuneatus of the cervical spinal cord and in peripheral white matter of cervical, thoracic, and lumbar segments. Additionally, the ventral gray columns and brain stem nuclei contained rare chromatolytic neurons with abnormal neurofilament accumulation. Leptomeninges of the cervical spinal cord were focally adhered to the dura and thickened by fibrosis and osseous metaplasia. Vitamin A deficiency was diagnosed based on hepatic vitamin A concentration of 1.71 μg/g dry weight. Adequate hepatic vitamin A concentration for yearling to adult domestic animals ranges between 150 and 1,000 μg/g dry weight. Lesions were distinct from those previously described in young captive lions with vitamin A deficiency, which had thickened skull bones and cerebellar herniation. The pathogenesis of vitamin A–associated myelopathy in this lion may be similar to that described in adult cattle, which is believed to result from spinal cord compression secondary to elevated pressure of cerebrospinal fluid.