For Part 7 in the series I have chosen to discuss Degenerative Myelopathy, previously known as Chronic Degenerative Radiculomyelopathy (CDRM), a neurological condition in which the spinal cord degenerates over time.
What is Degenerative Myelopathy?
Degenerative Myelopathy (DM) is a progressive degenerative disease of the spinal cord, meaning that over time part of the spinal cord breaks down. As the disease progresses, the signals from the spinal cord to the hindlimbs are not properly transmitted, causing weakness and eventually paralysis. The disease has been compared to a form of Motor Neuron Disease in humans.
What causes Degenerative Myelopathy?
DM is linked to a genetic abnormality in dogs - a genetic mutation in a gene which codes for a specific protein called superoxide dismutase. This protein's job is to destroy molecules in the body called free radicals, which are part of the body's natural defence mechanism. When there are too many free radicals in the body they can become harmful, which is what happens in DM cases as the protein to break them down is not produced.
According to current research, if a dog has two copies of the mutated gene, they are at a higher risk of developing DM, but having two copies does not make it inevitable. Dogs with only one copy of the mutated gene are 'carriers' of the disease, and are less likely to develop it.
Due to the genetic nature of DM, DNA testing is available to identify whether a dog is clear, a carrier, or at risk, but the the result does not confirm the dog will develop DM in all cases. Testing for at risk breeds is important prior to breeding, especially as the disease generally develops after the recommended breeding age. By screening for the mutated gene the prevalence in the canine population can be reduced.
DM was previously thought as a condition of the German Shepherd, but it does present in many other breeds including; Corgis, Boxers, Rhodesian Ridgebacks, Bernese Mountain Dogs and Wire Fox Terriers, to name a few.
What's happening inside the spine? (the science bit)
In the healthy nervous system the spinal cord acts as a switch board, helping to send messages between the body and the brain to create movement. The spinal cord is made up of two tissues - white and grey matter. White matter contains long fibres called axons which act as wires, transmitting nerve impulses to or from the brain. To speed up the transmission, axons are also insulated with a substance called myelin sheath.
In DM, the white matter in the spinal cord slowly degenerates, and the myelin sheath and axons are lost. It is thought that this is caused by the excess free radicals in the body. Due to the degeneration, the signals between the brain and the body are no longer transported, which is why dogs start to look uncoordinated and wobbly, progressing to complete paralysis.
Symptoms
Generally DM presents in dogs over the age of 5, and signs usually begin to show around the age of 8. In the early stages, DM can often be mistaken for other orthopaedic conditions, such as osteoarthritis of hip dysplasia, but as the disease progresses the signs become clearer.
In the early stages you may observe;
- Weakness of one hindlimb
- An ataxic gait - 'drunken sailor' walk, uncoordinated or 'wobbly'
- Dragging of hindlimb paws - wearing nails down, grazing paws
- Crossing over the hindlimbs when walking
- Falling over when turning or reluctant to turn
- Loss of muscle in the hindlimbs
As the disease progresses the above signs will worsen and progress to;
- Paralysis of the hindlimbs
- Incontinence
Despite the cruel nature of the disease, DM is a non painful condition, however it is important to consider that as the hindlimbs weaken, the forelimbs will take more weight, so the muscles can become overworked and sore.
If you observe any of these signs in your dog and you are worried please speak to your vet for further examination.
Treatment
Sadly DM is irreversible and progressive with no cure currently available, so the main aim of veterinary intervention is to support the dog and maintain quality of life for as long as possible.
In some cases, aids such as slings, wheels or carts can be introduced to allow the dog more freedom to exercise as the condition progresses. It is also important to protect the paws from damage with socks or boots, as the dog begins to drag more.
How can physiotherapy help?
The aim of physio in DM cases is to maintain the dog on their feet for as long as possible, as well as addressing any secondary pain, with correct management as the symptoms progress. Dogs can remain ambulatory for months or sometimes years after diagnosis, and recent research has shown how therapy can benefit cases of DM.
One trial split dogs into 3 groups - intensive physiotherapy, moderate physiotherapy, and no physiotherapy - and recorded the average survival time (Kathmann et al., 2006). The prescribed physiotherapy included; active exercises such as lead walking, sit to stands and weight shifting, passive range of motion exercises, massage, and hydrotherapy, as well as support with slings and bandages/socks for the paws. The results showed that dogs that underwent intensive physiotherapy had a longer average survival time (255 days) compared to the moderate group (130 days) and the no physio group (55 days).
Another more recent piece of research has investigated the benefits of LASER therapy alongside physiotherapy for DM (Miller et al., 2020) to aim to increase the time between diagnosis and euthanasia. The dogs included were prescribed two visits to the rehab clinic per week for LASER and hydrotherapy, with an additional home exercise programme including; stretching, standing and core exercises, pole work, and massage. The results showed the a combination of LASER treatment and physio had a significant beneficial impact on the progression of symptoms and survival times, averaging at 38.2 months between symptom onset and euthanasia. The research is really promising, and we can only hope that this will further progress to one day finding a cure for DM.
For more information on how physiotherapy could benefit your dog with Degenerative Myelopathy please get in touch - vetphysionancy@outlook.com // 07795163445.
Prognosis
DM inevitably progresses with symptoms worsening over time. Your vet will be able to help you determine the most appropriate options for your dog. For me, DM cases are one of the hardest, as I know the dog will never recover, but I am hopeful that research will lead to a cure in the future, and for now I hope I can help to manage this condition as well as possible in the dogs I treat.
If you want to know more about this condition please get in touch, any feedback is always appreciated. If you are dealing with a DM diagnosis and would like help please contact me - Nancy
M: 07795163445
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