Degenerative Myelopathy (DM) is an autoimmune disease in which the immune system attacks the central nervous system.  It was first described as a specific degenerative neurologic disease in 1973.  The attack leads to the degeneration of the myelin Sheath (insulation) and Axions (Nerve fibres).  It is said to be equivalent to the human disease Multiple Sclerosis.  The age of onset is 5 to 14 years (usually 8-9), which corresponds to the third to sixth decades of human life.  Although a few cases have been reported in other large breeds of dogs (Belgium Shepherds, Old English Sheepdogs, Rhodesian Ridgebacks, Weimaraner and the Great Pyrenees), the disease appears with relative frequency only in the German Shepherd breed (GSD), suggesting that there is a genetic predisposition for GSD in developing DM.

The first signs of DM are worn down toenails of a hind paw or dragging/knuckling of a hind paw.  It is characterized by ataxia, (a loss of coordination in the hind limbs). Affected dogs usually show a slowly progressive hind limb lack of coordination, clumsiness, and weakness.  The hind limbs start to cross over and trip the dog up.  The dog does not appear to know where his feet are.  As the disease progresses, the limbs become weak and the dog begins to buckle at the knees and have difficulty standing.  Usually a dog will lose complete mobility of the hind legs around 8 months from the onset, although it has not been unknown for some dogs to still be walking 2/3 years later.  This is a progressive disease, which can progress at different rates for different dogs.  The disease does have a tendency to wax and wan.  Once a dog has lost mobility of the hind quarters the disease starts to progress toward forelimb paralysis, and eventually brainstem failure.  The dog will become incontinent during the course of the disease, usually towards the latter stages.  

While diagnosis of DM is made by a history of progressive spinal ataxia (a loss of coordination) and weakness that may have a waxing and waning course or be steadily progressive, there are no specific tests for DM.  Ruling out other diseases that might cause the symptoms makes a DM diagnosis.    This is supported by the neurologic findings of a diffuse thoracolumbar spinal cord dysfunction.  The gross pathologic examination of dogs with DM generally is not contributory toward the diagnosis, although spinal radiographs and immune studies are used with some success.  The striking features being the reduction of rear limb and caudal (pertaining to the tail or the hind part) axial (comprised of bones in the trunk) musculature.

The treatment of DM involves four basic approaches:

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