Degenerative Myelopathy

Degenerative Myelopathy GSDs

by R.M. Clemmons, DVM, PhD
Associate Professor of Neurology & Neurosurgery
Small Animal Clinical Sciences

The Disease:
Degenerative Myelopathy (DM) was first described in 1973 as a specific degenerative neurologic disease.

The classic presentation of Degenerative Myelopathy is a painless, slowly progressive rear limb weakness or paralysis. There may be discomfort due to arthritis in the hip or lower lumbar (lower back) area, but this usually improves with activity. Over days, weeks, or months the dog becomes progressively weaker as is evidenced by shuffling of the rear limbs and lack of coordination. Finally, full paralysis coupled with fecal and urinary incontinence develops. The final stage is inability to empty the bladder and kidney failure due to chronic infection.

The age at onset is 5 to 14 years, which corresponds to the third to sixth decades of human life. Although a cases have been reported in other breeds of dogs, the disease appears with relative frequency in the German Shepherd breed, suggesting that there is a genetic predisposition for German Shepherd dogs (GSD) in developing DM. The work presented here and by others on the
nature of DM has been performed in the German Shepherd breed. Care must be taken in extrapolating this information to other breeds of dogs. Many dogs may experience a spinal cord disease (myelopathy) which is chronic and progressive (degenerative); but, unless they are caused by the same immune-related disease which characterizes DM of GSD, the treatments described herein may be ineffectual. 

Diagnosis of DM is made by a history of progressive spinal ataxia and weakness that may have a waxing and waning course or be steadily progressive. This is supported by the neurologic findings of a diffuse thoracolumbar spinal cord dysfunction. Clinical pathologic examinations are generally normal except for an elevated cerebral spinal fluid (CSF) protein in the lumbar cistern. Electromyographic (EMG) examination reveals no lower motor unit disease, supporting the localization of the disease process in the white matter pathways of the spinal cord. Spinal cord evoked potentials recorded during the EMG do show changes which help determine the presence of spinal cord disease. Radiographs of the spinal column including myelography are normal (other than old age changes) in uncomplicated DM. Unfortunately, myelography can be associated with worsening of clinical signs and carries some degree of risk for certain patients.

During the past two decades, we, at the University of Florida, have provided important new insights into the pathoetiology of DM. The release of antigens during the disease process could explain the immune deficits seen in DM and suggests that processing these immune-complexes by circulating macrophages leads to the development of the circulating suppressor cells that were previously noted. 

Alvin has crossed over rainbow bridge with the assistance of one of our vets. He had several medical problems as he was heartworm positive, had an enlarged heart with severe murmur and a progressive neurological disease called Degenerative Myelopathy (frequently shortened to DM)and was losing control of his rear end. 

Alvin from South FL, was an older male 6 to 8 years old that was turned in by people that said he was a stray when they brought him to a shelter in a county other than where they said they found him. His owners did not claim him. (We hate to think this whole story was a ruse and they took him to the shelter to die). He had a wonderful temperament, enjoyed being with people greeting everyone with a wagging tail.