Degenerative Myelopathy (CDRM)
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This disease is characterized by a slow, progressive degeneration of the fibres carrying messages up and down the spinal cord. It is commonly seen in older German Shepherds. Affected dogs gradually lose control over their back legs and have a swaying wobbly hind leg gait. Causes
Possible causes that have been looked at but not proven include:
- Genetics - suspected, but not proven, hereditary basis- German shepherds, German shepherd mixed breeds, and Siberian huskies
- Vitamin B12 or vitamin E deficiency
- Increase in circulating suppressor T lymphocytes
- An autoimmune response to a neural antigen, and dying-back neuropathy
CDRM is the most common cause of pelvic limb paresis in middle-aged, German shepherds and German shepherd mixed breeds
It is rare in other breeds of dogs and in cats.
Most commonly affected- German shepherds and German shepherd mixed breeds
Other large and medium breeds are occasionally affected.
Mean Age and Range
Mean age of onset: 9.6 years
Range: 4–14 years
German shepherds: two cases reported at 6 and 7 months old.
- CDRM has an insidious onset.
- It usally affects both hindlges, but is not necessarily symmetrical.
- Initially there is a mild weakness and inco-ordination of the hindlegs.
- Owners often bring their dog in for examination several months after onset of clinical signs, suspecting arthritis.
- Dogs display knuckling and scuffing of the toes of the hindlegs.
- The hindlegs cross over and there is swaying of the rear quarters- often when turning.
- Urination and defecation: voluntary control are retained until extremely late in the disease.
- Wastage of the hindleg and pelvic muscles occurs from none use.
- There is no pain or discomfort.
- Intervertebral disc protrusion and spinal neoplasia—most likely to resemble degenerative myelopathy; back pain at the lesion site is common but may not be observed; differentiated by survey radiography and myelography.
- Myelitis—usually more acute and progressive; ruled out by CSF analysis at the time of myelography.
- Discospondylitis—differentiated by occurrence of back pain; survey radiography helpful.
- Lumbosacral stenosis—generally causes pain; to rule out, may need electromyography and epidurography.
- Vertebral spondylosis and dural ossification—common radiographic findings in old, large-breed dogs; almost never cause clinical signs.
- Thoracic and abdominal radiography—screen for metastatic disease; consider the age of the patient and the possibility of spinal neoplasia.
- Spinal survey radiography—generally normal; may reveal dural ossification or spondylosis; findings are generally of no clinical significance.
- Nursing care.
- Dog should be encouraged to be active as long as possible to delay onset of a non-ambulatory state.
- Non-ambulatory patients—pay careful attention to prevent pressure sores; provide good bedding.
- A cart may be beneficial.
- Avoid excess weight.
- Encourage exercise to prevent muscle atrophy; the stronger and more active the patient is, the longer it will stay ambulatory as the paresis progresses.
No effective surgery available
It is possible for a dog to have concurrent type II disk protrusion; unless the spinal cord compression caused is extreme, surgery should not be done until a therapeutic trial of corticosteroids is completed; if marked improvement is seen, then decompressive surgery is warranted.
Drugs of choice
No proven effective treatment available
Proposed treatment—suggested by one author; combination of exercise, vitamin supplements, and epsilon aminocaproic acid (Amicar, Lederle, NY; 500 mg PO q8h mixed with a hematinic compound); apparently slows the progression in 50% of patients; 15%–20% of patients do not deteriorate further if treatment is maintained; no controlled trials have been done.
Corticosteroids—do not use; not beneficial in the treatment of this disease.
Steroid myopathy—may worsen muscle atrophy and pelvic limb weakness, hastening the onset of a non-ambulatory state.
Pressure sores and urine scalding once a non-ambulatory state is reached.
CDRM is is a non-treatable disease that progresses slowly and steadily.
Euthanasia is recommended once a non-ambulatory state is reached.
Most affected dogs gradually lose function in the pelvic limbs, reaching a non-ambulatory state within 6 months to 2 years after onset.
Non-ambulatory patients eventually lose thoracic limb function and may develop urinary and faecal incontinence.