What is Degenerative Myelopathy in Pets?
Canine degenerative myelopathy (DM) is an uncommon, progressive degenerative disease that causes hind limb weakness and paralysis and eventually affects the front limbs, as well. The symptoms of DM start gradually, usually in adult dogs over 5 years of age. Early in the course of the disease, affected dogs will start to lose muscle coordination and balance in their rear legs (ataxia). They will develop slight or incomplete hind end paralysis (paraparesis), which will progress to total rear end paralysis (paraplegia), accompanied by varying degrees of urinary and/or fecal incontinence. As the dog loses its ability to stand and use its hind legs, it may develop bed sores and wounds from urine scalding, which can be extremely painful. It usually takes somewhere between 6 and 12 months for full pelvic paralysis to develop in dogs with DM. The front legs will be affected next, starting with lack of coordinated movement (ataxia) and progressing to complete paralysis. The ability to chew and swallow can also be affected. When all 4 legs are paralyzed, the condition is called “tetraplegia.” Tetraplegia usually occurs within several years of the diagnosis. The dog’s sensory perception abilities are unaffected by this disease, and most affected dogs do not suffer from pain.
Darryl L. Millis, MS, DVM, DACVS, DACVSMR, CCRP
Professor of Orthopedic Surgery & Director of Surgical Service
Robin Downing, DVM, MS, DAAPM, DACVSMR, CVPP, CCRP
Diplomate of the American Academy of Pain Management, is a a founder and past-president of the International Veterinary Academy of Pain Management.
Janet B. Van Dyke, DVM
Diplomate American College of Veterinary Sports Medicine and Rehabilitation, CCRT, CEO
Ludovica Dragone, DVM, CCRP
Vice President of VEPRA, Veterinary European of Physical Therapy and Rehabilitation Association.
Andrea L. Henderson, DVM, CCRT, CCRP
Resident, Canine Sports Medicine and Rehabilitation
Steven M.Fox, MS, DVM, MBA, PhD
President Securos. Inc
What causes Degenerative Myelopathy in Dogs and are there certain breeds at risk?
Degenerative myelopathy begins with the spinal cord in the thoracic (chest) region. If we look under the microscope at that area of the cord from a dog that has died from DM, we see degeneration of the white matter of the spinal cord. The white matter contains fibers that transmit movement commands from the brain to the limbs and sensory information from the limbs to the brain.
This degeneration consists of both demyelination (stripping away the insulation of these fibers) and axonal loss (loss of the actual fibers), and interferes with the communication between the brain and limbs. Recent research has identified a mutation in a gene that confers a greatly increased risk of developing the disease.
Degenerative myelopathy is most often diagnosed in aging German Shepherds. Other breeds that have been reported with DM include the American Eskimo, Belgian Shepherd, Bernese Mountain Dog, Boxer, Cardigan Welsh Corgi, Chesapeake Bay Retriever, Collie, Giant Schnauzer, Golden Retriever, Great Dane, Irish Setter, Irish Terrier, Kerry Blue Terrier, Kuvasz, Labrador Retriever, Miniature Poodle, Old English Sheepdog, Pembroke Welsh Corgi, Pug, Rhodesian Ridgeback, Siberian Husky, Soft-Coated Wheaten Terrier, Standard Poodle, Weimaraner and Wirehaired Fox Terrier. Mixed breed dogs have also been diagnosed with this disease. The mean age of affected dogs is 9 years, with males and females being affected equally. It is extremely uncommon for young dogs to develop DM.
In the section of a spinal cord from a dog who has died of DM (Left), the degeneration is seen as a loss of the blue color at the edges (arrows) compared with the spinal cord from a normal dog which is blue througout (Right).
Signs and Symptoms of Degenerative Myelopathy in Dogs
Owners of dogs with degenerative myelopathy may notice one or more of the following signs as their dog’s disease progresses:
- Dragging of the rear paws; knuckling-over on the rear toes
- Sores on top of the rear paws
- Abnormal wear of the rear toenails
- Lameness; limping (starts in the hind end; progresses to the forelimbs)
- Spastic, long-strided rear movement
- Difficulty jumping, running, rising or walking
- Balance and coordination abnormalities (ataxia)
- Muscle wasting of the hindquarters from disuse and neurogenic atrophy; mild to progressively profound
- Incomplete paralysis of the hind legs (paraparesis)
- Complete paralysis of the hind legs (paraplegia); inability to stand or walk
- Incontinence (urinary and/or fecal)
- Urine scalding
- Bed sores
- Incomplete paralysis of all legs (tetraparesis)
- Complete paralysis of all four legs (tetraplegia)
- Difficulty chewing or swallowing
- Difficulty breathing
Some owners mistakenly assume that their older pets are developing arthritis, when DM is actually the culprit. Affected animals usually become incontinent late in the course of the disease, although they do not seem to be painful. In fact, one of the key clinical features of canine degenerative myelopathy is the absence of any localizable spinal pain.
Degenerative Myelopathy – The importance of a proper diagnosis process
Canine degenerative myelopathy (DM) is a fairly uncommon but potentially fatal spinal cord disease that can be difficult to diagnose. A number of other disorders mimic the signs and symptoms of DM, including intervertebral disk disease, myelitis, degenerative lumbosacral stenosis, spinal cord neoplasia (cancer) and hip dysplasia, among others. A veterinarian presented with a dog showing hind limb lameness, lack of coordination, muscle wasting and partial paralysis must first rule out other causes of the dog’s condition before reaching a presumptive diagnosis of degenerative myelopathy. She will take a thorough history from the dog’s owner, focusing on when, where and how the dog’s symptoms first came to light. She will also perform a thorough physical examination, including a neurologic examination if she is skilled in that area, to try and localize which parts, if any, of the spinal cord have been damaged or are otherwise involved. The initial evaluation may include routine blood and urine assessment (complete blood count, serum chemistry panel and urinalysis). The results of those tests typically will be unremarkable if DM is the underlying cause of the dog’s condition.
A comprehensive neurological examination is critical to making a tentative diagnosis of degenerative myelopathy. Dogs with this disease are not painful, and a skilled veterinarian can localize their spinal cord lesions to the upper and lower back (thoracic and lumbar) areas. Survey X-rays of the chest and back (thoracolumbar radiographs) can be taken to screen for primary or metastatic cancer. The veterinarian will review the radiographs carefully, looking for any evidence of tumors along or around the spinal cord that may be contributing to the dog’s symptoms. Samples of cerebrospinal fluid can be analyzed for evidence of inflammation. Advanced imaging procedures, such as electromyography, myelography, nerve conduction studies, computed tomography (CT) scan and magnetic resonance imaging (MRI), can be performed alone or in combination to rule out other disorders. A test is now available to detect the presence of the genetic mutation that is responsible for causing degenerative myelopathy in dogs. Normal dogs will have two copies of the non-mutated gene; this is called being “homozygous” for the normal gene. Carriers will have one copy of the normal gene and one copy of the mutated gene, one coming from each parent; this is called being “heterozygous” for that gene. Dogs that have or are at risk for having DM will have two copies of the mutated gene; they will be “homozygous” for the mutated gene. All dogs with DM will have two of the abnormal genes, but not all dogs with two of the abnormal genes will develop DM.
In a living animal, degenerative myelopathy can only be diagnosed by ruling out other causes of progressive, irreversible paralysis. Unfortunately, the only definitive way to diagnose this disease is to examine the dog’s spinal cord under a microscope after the animal has died. This is done at a diagnostic pathology laboratory using a technique called histopathology.
The importance of Rehabilitation and Physiotherapy for Dogs with Degenerative Myelopathy
Degenerative Myelopathy (DM) is a progressive disease and physiotherapy and hydrotherapy can be involved at any stage. For optimum care, early intervention is key.
The main aim of rehabilitation of degenerative myelopathy is to delay progression of the condition and enhance quality of life.
Consideration needs to be paid to:
- Maintenance of mobility and gait patterns
- Prevention of any tightening of soft tissues such as tendons, muscles and ligaments
- Maintenance of muscle mass
- Enhancement of balance and coordination
- Prevention of injury that might occur as a result of the existing issues.
The list of treatment options available in the management of DM is extensive but can include the following:
- Advice regarding exercise modification and avoidance of fatigue
- Active and passive exercises
- Strengthening of muscles using a combination of exercise, hydrotherapy and muscle stimulation
- Very occasionally pain relief using Hydrotherapy Treatment Options:
Water based exercise in the pool, on the underwater platforms or in the underwater treadmill is a crucial part of rehabilitation when a dog presents with DM. The buoyancy of the water provides support against gravity and allows more effective exercise of the weakened areas of the body. Depending on the severity of your dogs clinical signs, the amount of support can be varied affecting how much effort will be needed to complete the exercises.
|Timeline||Physiotherapy Aims||Rehabilitation Therapy options|
|Week 0 to 2||Introduction to Water Therapy for dogs|
|Week 2 to 4||Progress limb loading and gait re education|
|Increase muscle mass|
|Maintain soft tissue length and flexibility|
|Management at home|
|Week 4 to 6||Continue as above|
|Week 6 to 12||Increase exercise tolerance||Increase exercise level, considering land and water based options.|
|Continue to increase core stability||Home exercise program considering land and water based exercises|
|Week 12 onwards||Return to full function or establish deficits and advise regarding long term management.||Progress to off lead exercise and previous exercise level if appropriate.|