Degenerative Myelopathy: Not Just in German Shepherds

The purpose of the study reported in this paper was to characterize the clinical signs and histopathology of familial degenerative myelopathy (FDM) in Pembroke Welsh corgis (PWCs). Progressive asymmetric pelvic limb ataxia and paresis and lack of paraspinal hyperesthesia are indicative of degenerative myelopathy (DM). Age of onset of neurologic signs is > 5 years, with a mean age of 9 years. Definitive diagnosis of DM is determined postmortem by histopathologic examination of the spinal cord. Clinical progression of FDM in PWCs was similar to that observed in other breeds, although the duration was longer (19 mo vs 6 mo). All dogs were nonambulatory, paraparetic or paraplegic, and 15 (of 21) dogs had thoracic limb weakness at the time of euthanasia. Pathologic changes of the spinal cord in FDM-affected PWCs were consistent with a noninflammatory axonal degeneration. Axonal and myelin degeneration was most severe in the dorsal portion of the lateral funiculus. Histopathologic lesions were located in all funiculi but were consistently more severe in specific regions of white matter funiculi, which would explain the clinical neurologic signs of proprioceptive loss and paresis in the pelvic limbs. Lesions found in the dorsal funiculus of dogs in this study may contribute to a lack of visceral sensory feedback to brain centers, which would result in loss of recognition of rectal distention, bladder distention, or both, and eventual involuntary evacuation of feces or urine. A diagnosis of DM is highly suspected in dogs with progressive paraparesis without paraspinal hyperesthesia and no evidence of compressive myelopathy on myelography or MRI. The pathogenesis and cause of canine DM are unknown, but information presented in this paper appears to support a familial disease.

COMMENTARY: This article illustrates very clearly that degenerative myelopathy can affect purebred dogs other than the classic example of the German shepherd. A very careful neurologic examination to evaluate reflexes and spinal hyperpathia could help sort out some differentials for progressive ataxia and/or paresis in the pelvic limbs. If an older PWC presents with pain over a specific vertebra, such differentials as intervertebral disk disease or a tumor may be more likely. MRI would be necessary to visualize changes that could differentiate between degenerative myelopathy and other forms of spinal cord disease. Although the long-term prognosis for this disease is poor, it is helpful to know that these dogs could be more easily managed than other breeds because of their small size.

Clinical characterization of a familial degenerative myelopathy in Pembroke Welsh corgi dogs. Coates JR, March PA, Oglesbee M, et al. J VET INTERN MED 21:1323-1331, 2007.