Canine Degenerative Myelopathy

What is Canine Degenerative Myelopathy?

Canine degenerative myelopathy is a progressive neurodegenerative disease that affects the spinal cord, specifically the area that controls the hind limbs. It is caused by the degeneration of the white matter of the spinal cord, which leads to the loss of nerve function. Over time, the degeneration spreads, leading to weakness, incoordination, and paralysis in the dog’s back legs.

DM is often compared to amyotrophic lateral sclerosis (ALS), or Lou Gehrig's disease, in humans because it similarly affects the motor neurons responsible for muscle control and movement. The disease does not affect the dog’s brain but targets the spinal cord and nerves leading to the muscles, ultimately causing them to atrophy (shrink) and lose function.

The disease is typically diagnosed in older dogs, with most cases appearing in dogs over 8 years of age. The progression of DM can be slow, but it is ultimately fatal, as it severely affects the dog’s ability to move and function.

     

Causes of Canine Degenerative Myelopathy

The exact cause of degenerative myelopathy is not fully understood, but researchers believe that it is linked to a genetic mutation in the SOD1 gene, which is responsible for producing an enzyme called superoxide dismutase 1. This enzyme is essential for protecting cells from oxidative damage. In DM, the mutation causes this enzyme to malfunction, leading to the degeneration of nerve cells in the spinal cord.

While genetic predisposition plays a key role in the development of DM, environmental factors or other health conditions may also contribute to its onset or accelerate its progression. It is believed that the disease may be triggered by a combination of genetic and environmental factors, although this has not been definitively proven.

Canine Degenerative Myelopathy Symptoms

The symptoms of canine degenerative myelopathy can be subtle at first, gradually worsening over time. Pet owners may notice changes in their dog’s walking patterns, coordination, and overall mobility. Early signs of the disease often include:

1. Weakness in the Hind Legs

One of the earliest symptoms of DM is a noticeable weakness in the dog’s hind legs. Dogs may start dragging their back paws, particularly on one side, and may be seen “scraping” the ground while walking. Over time, this weakness can progress to complete paralysis in the back legs.

2. Loss of Coordination (Ataxia)

As the disease progresses, dogs may experience a lack of coordination, known as ataxia. The dog may appear wobbly or unsteady while walking, as if they are unable to control their hind limbs. This is due to the breakdown of nerve function in the spinal cord.

3. Difficulty Rising or Climbing Stairs

Dogs with DM may begin to have difficulty getting up from a lying position, climbing stairs, or jumping onto furniture. The loss of strength in the hind limbs makes it harder for the dog to perform these basic movements.

4. Tremors

Some dogs with degenerative myelopathy may exhibit mild tremors or shaking in their hind legs as the disease affects the spinal cord. These tremors can be more noticeable when the dog is standing or trying to move.

5. Muscle Atrophy

As the disease progresses, the muscles in the hind legs may begin to shrink or waste away due to lack of use. This can make the dog’s legs appear thin and weak, and may lead to further loss of mobility.

6. Incontinence

In the later stages of DM, some dogs may experience urinary and fecal incontinence. This is due to the nerve damage affecting the dog’s ability to control bladder and bowel movements.

7. Pain or Sensitivity

Unlike other neurological disorders, degenerative myelopathy is typically not painful, but some dogs may experience discomfort due to muscle strain or joint issues related to their lack of mobility.

Canine Degenerative Myelopathy Stages

Degenerative myelopathy progresses through several stages, with symptoms becoming more severe as the disease advances. The stages of DM are usually divided into four stages:

Stage 1: Early Signs

In the early stages of DM, dogs may show mild weakness or wobbling in their hind legs. The symptoms are subtle, and the dog may still be able to walk short distances without difficulty. At this point, pet owners may notice occasional dragging of the feet, but the dog’s quality of life is not yet severely impacted.

Stage 2: Moderate Symptoms

As the disease progresses, the symptoms become more noticeable. The dog may experience more significant weakness and coordination issues in the hind legs, making walking and climbing stairs difficult. Muscle atrophy begins to set in, and the dog may begin to lose its balance when walking.

Stage 3: Severe Mobility Loss

In this stage, the dog’s mobility is significantly compromised. The dog may have trouble walking or standing and may start to fall frequently. The hind legs may become completely paralyzed, and the dog may require assistance in getting up or moving around.

Stage 4: Complete Paralysis

By the fourth and final stage, the dog may become completely paralyzed in the hind limbs. Incontinence becomes more pronounced, and the dog may have difficulty eating or drinking without assistance. The dog’s quality of life declines significantly, and euthanasia is often considered at this stage.

Canine Degenerative Myelopathy Test

If your dog is exhibiting signs of weakness or loss of coordination, it is important to consult with a veterinarian for a proper diagnosis. Canine degenerative myelopathy can be difficult to diagnose based on clinical symptoms alone, as its early signs can mimic those of other neurological disorders.

Genetic Test

The most reliable test for DM is a genetic test to detect the presence of the mutated SOD1 gene. This test is performed using a blood or cheek swab sample. If your dog tests positive for the gene mutation, it indicates a genetic predisposition to the disease, although not all dogs with the mutation will necessarily develop DM. If the test is negative, it rules out DM as a potential cause of the symptoms.

Exclusion of Other Conditions

Since DM shares symptoms with other conditions, such as intervertebral disc disease (IVDD), hip dysplasia, or arthritis, a veterinarian will also need to rule out these possibilities through imaging studies (X-rays or MRIs) and other tests.

Neurological Examination

A comprehensive neurological examination is also essential to determine the location and nature of the neurological damage. A veterinary neurologist may assess the dog’s reflexes, coordination, and gait to pinpoint the exact source of the problem.

Canine Degenerative Myelopathy Treatment

Unfortunately, there is no cure for canine degenerative myelopathy. However, there are management strategies that can help slow the progression of the disease and improve the dog's quality of life, especially in the earlier stages.

1. Physical Therapy

Physical therapy is one of the most effective ways to help dogs with DM maintain strength and mobility. Regular exercise, stretching, and range-of-motion exercises can help preserve muscle mass and improve coordination. Hydrotherapy (swimming) is particularly beneficial as it provides a low-impact environment for exercise and can help with balance and muscle strengthening.

2. Assistance Devices

As the disease progresses, dogs may need assistance with mobility. Walkers, carts, and other assistive devices can help dogs move around more easily and maintain independence. These devices can also help prevent further muscle atrophy caused by immobility.

3. Anti-inflammatory Medications

Non-steroidal anti-inflammatory drugs (NSAIDs) may be prescribed to manage pain and inflammation, especially if the dog experiences joint pain due to altered movement patterns.

4. Nutritional Support

Providing a balanced, nutrient-rich diet can help maintain overall health and support muscle mass. Some veterinarians recommend supplements like omega-3 fatty acids and antioxidants to promote nerve health and reduce oxidative stress on the nervous system.

5. Euthanasia Consideration

As degenerative myelopathy is a progressive, terminal disease, euthanasia may become a consideration when the dog reaches the final stages of the disease. If the dog’s quality of life deteriorates to the point where it is no longer able to move or perform basic functions (such as eating, drinking, or eliminating waste), euthanasia may be the kindest option to prevent suffering.

Canine Degenerative Myelopathy Breeds

While any dog can develop degenerative myelopathy, certain breeds are more predisposed to the disease due to genetic factors. The following breeds are most commonly affected by DM:

1. German Shepherds
2. Boxers
3. Pembroke Welsh Corgis
4. Chesapeake Bay Retrievers
5. Golden Retrievers
6. Shetland Sheepdogs
7. Irish Setters
8. Doberman Pinschers

Owners of these breeds should be particularly vigilant in monitoring for symptoms of DM, especially as their dogs age.

When to Euthanize a Dog with Degenerative Myelopathy

Deciding when to euthanize a dog with degenerative myelopathy is one of the most difficult decisions a pet owner will ever face. It is essential to focus on the dog’s quality of life and overall comfort.

Some signs that it may be time to consider euthanasia include:

• Complete paralysis in the hind limbs
• Inability to eat, drink, or relieve itself
• Significant pain or distress
• Inability to stand or walk even with assistance
• Loss of interest in life or interacting with family

Discussing options with your veterinarian and considering the dog’s well-being and comfort is crucial during this difficult decision-making process.

Conclusion

Canine degenerative myelopathy is a heartbreaking condition that can drastically change the life of both the dog and its owner. While there is no cure, understanding the disease, its symptoms, and the available management options can help improve the dog’s quality of life and guide owners in making informed decisions. Regular veterinary care, genetic testing, and physical therapy can slow the progression of the disease, and assistive devices can provide support as the dog’s condition worsens. Ultimately, when the time comes to say goodbye, euthanasia can be a compassionate way to prevent further suffering and ensure the dog’s dignity and peace.