Intramedullary cavernous malformation of the spinal cord in two dogs.

Intramedullary cavernous malformations (CVMs) of the spinal cord were diagnosed in 2 adult dogs that presented for paraparesis. An intramedullary spinal cord lesion was identified on a myelogram in the first dog, and expansion of the vertebral canal was evident on radiographs in the second. Extensive intraparenchymal hemorrhage was found on gross postmortem examination in both dogs, and a distinct lobulated intramedullary mass was evident in the second dog. Microscopically, both lesions were composed of dilated, thin-walled vascular channels with little-to-no intervening neural parenchyma. Both dogs had evidence of channel thrombosis along with perilesional hemorrhage and hemosiderin accumulation. The second dog had additional degenerative changes, including thickened fibrous channel walls with hyalinization, foci of mineralization, and occasional tongues of entrapped gliotic neuropil. CVMs appear to be an uncommon cause of both acute and chronic spinal cord disease in the dog.