Degenerative myelopathy in dogs: symptoms and care

Overview

Degenerative myelopathy is a progressive neurological disease of the spinal cord in older dogs. Symptoms most often start at around 8 years of age or later. A typical age range at onset of 8–14 years is also given. The first changes usually affect control of the hindlegs.

The disease often starts in one hindleg before affecting both. A dog may lose the ability to walk within 6–12 months of symptoms starting. Gradual progression distinguishes the usual course from many sudden spinal cord injuries. However, several other diseases can cause similar weakness.

The disease shares features with human amyotrophic lateral sclerosis, or ALS, a degenerative disease of motor nerve cells.

Causes

Communication pathways in the spinal cord degenerate

Degeneration typically begins in the part of the spinal cord within the chest region. It affects the white matter, which carries messages between the brain and limbs. Nerve fibres, or axons, and their surrounding myelin degenerate in this area. Tissue examination shows non-inflammatory damage, rather than a typical inflammatory spinal cord disease.

When information about limb position is not transmitted normally, paw placement becomes inaccurate. Weakness gradually increases until the dog struggles to support its hindquarters. At a later stage, degeneration may also affect the front legs.

Myelin insulates nerve fibres, and its loss disrupts communication between the limbs and brain.

A gene variant increases susceptibility

In several breeds, disease risk is associated with a variant in the SOD1 gene. A recognised risk variant of this gene is SOD1A. Dogs with two altered copies have a greater risk of disease, but not all of them become affected. Other inherited factors, and possibly the environment, also influence whether disease develops.

The SOD1 gene is associated with an enzyme that helps protect cells against oxygen free radicals. Some altered proteins are poorly soluble and may harm nerve tissue.

Risk factors

Older age is a common feature in affected dogs. Breed susceptibility has been identified in German Shepherd Dogs and Collies, for example. However, the disease can occur in many other breeds. Finding the variant provides information about risk but does not, by itself, mean a symptom-free dog will develop the disease.

Genetic differences affecting age at onset may also be significant between breeds. A dog carrying one altered copy may also be at risk. The significance of the same variant must therefore be assessed alongside the dog's clinical condition.

Both sexes can develop symptoms, so a dog's sex does not rule out the disease.

Typical symptoms

Symptoms usually begin gradually and mainly affect use of the hindlegs.

• Hind claws wear down as the paws drag along the ground when walking.

• Your dog staggers, stumbles or sways through its hindquarters when walking.

• A hind paw knuckles over, so your dog stands on the top of the paw.

• Getting up from lying down or remaining standing becomes difficult.

• Stairs, getting into the car and longer walks become challenging.

• The hindleg muscles waste and your dog loses strength.

Bladder and bowel function are usually normal early on. Urinary or faecal incontinence may develop as the disease progresses. Your dog may become more restless or irritable as movement becomes harder.

The hindquarters may sway even when your dog stands still. A slight sideways nudge may cause it to lose its balance.

Complications and consequences

Dragging paws and claws can become damaged and painful. Urinary incontinence increases the risk of urinary tract infections. Skin left wet with urine may become irritated. Reduced mobility increases the need for pressure sore prevention and good basic care.

Many dogs are euthanased because of severe mobility loss within 6–12 months of symptoms starting. Average survival from diagnosis has also been described as 1–2 years. Without euthanasia, the disease may progress for more than 3 years and eventually impair breathing.

Repeated contact with the ground can wear hair off the tops of the paws and irritate the skin. Staggering and falls can cause secondary pain even though the spinal cord degeneration itself is painless.

Diagnosis at the vet

Ruling out other causes

No single test can definitively confirm degenerative myelopathy in a living dog. The vet assesses the onset and progression of symptoms and performs a neurological examination. Blood tests and imaging help investigate other possible causes of weakness. Cerebrospinal fluid testing may form part of a wider investigation.

Possible alternatives include a slipped disc, tumours, infections and previous spinal cord injuries. A slipped disc can compress the spinal cord and cause weakness or paralysis. Many such alternative causes can be treated effectively. Hindleg weakness should therefore not be assumed to be degenerative myelopathy on the basis of age or breed alone.

MRI, or CT when needed, is used to look for problems such as spinal cord compression. A presumptive diagnosis can be made if no other explanation is found. Confirmation requires microscopic examination of the spinal cord after death.

The neurological examination assesses walking, posture and how your dog corrects its limb positions. The spine is felt and limb reflexes tested to help locate the disease. Muscle tone and joint range of movement are also assessed to identify stiffness and other restrictions on movement.

Degenerative myelopathy can also occur alongside another neurological disease.

What the genetic test means

Genetic testing shows whether a dog has 1 or 2 altered copies associated with the disease. An at-risk result is therefore not the same as clinically diagnosed disease. Testing can be performed at any age. The result helps assess inherited susceptibility, but other investigations determine what explains the current symptoms.

Treatment

Rehabilitation and treatment of other conditions

Treatment aims to preserve your dog's abilities and comfort for as long as possible. Physiotherapy aims to maintain muscle mass and slow the decline in mobility. Gentle exercise and water-based rehabilitation may form part of an individual plan. However, exercise must stay within your dog's capacity, as activity is more tiring for an affected dog than usual.

Concurrent osteoarthritis or hip disease can further impair movement, and treating these may improve comfort. Maintaining a suitable body weight is part of everyday support. If urinary incontinence develops, the vet may check urine samples for infection. The fact that degeneration itself is painless does not remove the need to treat other painful or inflammatory problems.

Changes at home and mobility aids

Cover slippery floors with rugs or non-slip surfaces to stop weak hindquarters sliding out from underneath your dog. A support harness or sling under the abdomen may help with standing up and walking. Shallow ramps can make changes in level easier to negotiate. Protective boots may reduce damage to dragging paws.

Boots must be roomy enough not to constrict the paws. A cart supporting the hindquarters may help some dogs move around. Its usefulness also depends on how well the individual dog accepts it. A padded bed with low sides may be easier to use than one with high sides.

Limits of the evidence

Rehabilitation may support function, but firm evidence that it stops the degeneration itself is lacking.

An experimental combination of stem cell transplantation and intensive rehabilitation was evaluated in 13 dogs. Average survival in the combined treatment group was 438 days. Average survival in the more conventional rehabilitation group was 274 days. The small group size and allocation based on owner consent limited the comparison. Only 1 dog's diagnosis was confirmed by tissue examination.

The experimental combination treatment groups differed in both rehabilitation intensity and use of stem cell transplantation. A curative effect therefore cannot be inferred simply from a survival difference in a small group.

Prevention

Genetic testing can assess susceptibility before symptoms develop. Thoughtful use of genetic information in breeding can reduce inherited risk over the long term. Major decisions based only on an at-risk result are not justified without assessing the dog's wellbeing and quality of life. Some breed-club criteria for Finnish Lapphunds allow an at-risk dog to be mated only with a genetically clear dog. Otherwise, this genetic result does not affect approval of the mating under those particular breed criteria.

If the risk allele is common in a breed, reducing its frequency may take several generations.

Important for dog owners

Record when paw dragging or unsteadiness began and which leg was affected first. Short videos of the same walking route can help track everyday mobility. Bring previous spinal and joint images and any genetic test report to appointments.

Keep your dog's skin and bedding clean and dry if urine leaks. Reassess quality of life regularly, as severe mobility loss can reduce it considerably even without back pain.

Agree which changes call for reassessment and when mobility aids or home care need adjusting. Monitor whether your dog can rest in a dry place, get outdoors and take part in things it enjoys. Also discuss how much daily lifting and cleaning you can provide.

If your dog is suffering or its care needs can no longer be met, euthanasia may become part of a decision made with your vet.

Notice whether your dog remains interested in food, outings and company, or whether everyday movement is clearly a strain. Provide non-slip routes at home and a quiet place for assisted standing. Check the skin on the paws and the fit of support equipment at the same time.

Frequently asked questions

Is degenerative myelopathy painful?

The spinal cord degeneration itself is usually painless. However, a dog may also have osteoarthritis or painful injuries from dragging its paws. New pain needs investigation, as another condition may require its own treatment.

Does a genetic test confirm the diagnosis?

No: it shows the number of disease-associated gene variants and inherited susceptibility. Not every dog with two risk copies develops the disease. In a living dog, diagnosis relies on excluding other conditions that explain the symptoms; final confirmation comes from spinal cord tissue examination after death.

How quickly does walking ability deteriorate?

A dog may lose the ability to walk within about 6–12 months of symptoms starting. Symptoms often begin in one hindleg before spreading to both. Later, the front legs may also weaken, and some dogs develop urinary or faecal incontinence.

Can physiotherapy cure the disease?

Physiotherapy aims to maintain muscles and function, but there is no cure. The amount of exercise is tailored to your dog's capacity. Overly strenuous activity can tire an affected dog more than usual, so independently increasing exertion is not the aim of rehabilitation.

Could weak hindlegs be caused by a treatable condition?

Yes: slipped discs, infections, tumours and injuries, for example, can cause similar weakness. Many alternative conditions can be treated effectively. The cause should therefore be investigated even if your dog's breed, age or genetic result also fits degenerative myelopathy.