Degenerative Myelopathy (Degeneration of the Spinal Cord, DM) is an inherited defect where the immune system attacks the dog's central nervous system. This attack leads to a loss of insulation around the nerve fibers (myelin) and of nerve fibers (axons). Once the nerves in the spinal cord are destroyed, the dog can no longer walk because, without nerve connections, muscles cannot work. The control pathways that make muscles work are located all throughout the spinal cord.
DM is an insidious defect, the symptoms of which rarely show up before the age of 5, and possibly as late as age 14 years. The early stages of DM start with an almost imperceptible weakness in the hindquarters (also see 13, Hind Leg Weakness). In the last stage, the dog can no longer walk, nor hold balance when standing or squatting to defecate.
However, DM itself is not painful. There is zero pain because the nerve cells have died. The dog no longer feels the legs. A very stressful thought and physical experience, but without pain.
Who Gets Degenerative Myelopathy
German Shepherds are the breed that is most susceptible to Degenerative Myelopathy: Between 1 to 3% of German Shepherds worldwide are affected. However, in the USA alone, each year between 14,000 to 42,000 GSDs are diagnosed with DM - which effectively means that in the USA the proportion of affected GSDs is much higher. Simplified calculation: average 28,000 per year * average 12 years lifespan / 3.5 mio GSDs = 9.6%!
Since DM is hereditary, this means that GSD breeders have not yet taken enough care to avoid breeding affected parents. This reinforces the importance of finding the best German Shepherd breeders when you select your next GSD.
However, as with most inherited defects, both the outbreak of DM and its progression are triggered by dietary and environmental intoxication. This means that you can indeed delay the outbreak of DM and slow down or even stop progression if you provide the right living environment for your dog.
Recently, the cause of DM, a homozygous SOD1 A genetic abnormality has been identified. It is recessive which means both parents, the dam and the sire, must carry the defective gene for the puppies to develop DM later in their lives.
A simple saliva-based genetic test was developed which can help determine the risk that a certain dog may suffer DM later in life. The test costs only 65 USD.
This test is of course more relevant to those GSD breeders who aim to try their best to use breeding dogs without hereditary defects, however you too may wish to know whether your dog carries the defective A/A gene combination. In that case note that even a dog that carries the defective gene combination will not necessarily develop the symptoms of DM before the dog dies, because this depends on environmental triggers and on how early the dog dies.
During early stage DM, occasionally you can hear the sound of your dog's hind leg toe nails scraping over the pavement during walking. Your dog will begin to show some difficulty getting up. If the dog is standing, (s)he may have difficulty balancing, yet the dog can recover on his own. If you turn your dog's toes under, (s)he may still be able to right the foot pad-down, but response time may be lengthened.
As DM progresses, difficulty getting up and rear feet nail scraping will increase. The rear legs will cross under your dog's body since (s)he is losing sensation in the hindquarters: The dog does not know where (s)he has placed the feet. Faulty perception of foot placement leads to tripping and stumbling.
When your dog is in a standing position, if you move the dog from side to side using your hands, the dog will lose balance and topple over. Often, you will notice exaggerated movements, such as high stepping when going up a curb. If you now turn your dog's toes under, your dog will no longer place the foot in the proper pad-down position once (s)he can no longer feel the feet.
Soon, the tail will rarely become active and wag, however because of the length of the German Shepherd tail it may become tangled with the hind legs.
Ultimately, you will need to help a DM-suffering dog to walk at all. Up until the terminal phase, DM can take several years but ultimately the sense of feeling is completely lost, and the dog then loses control over bowel and bladder too.
Preventing Degenerative Myelopathy
Although there is still no cure for DM or medication that would replace lost myelin and repair damaged axons, recent research has brought quite dramatic changes to the life expectancy and quality of life of dogs with DM. All these improvements are centered around the goal to provide the dog with a living environment that will at least delay, and possibly prevent, the outbreak or progression of DM.
Treating Degenerative Myelopathy