Back (spinal) problems are common in dogs and some breeds of dog may be particularly at risk of particular types of spinal problem. Affected dogs may have neck or back pain or show a variety of signs including difficulty walking, jumping, using one or more legs or even complete paralysis. These signs may occur suddenly (acute spinal problem) or more progressively (chronic spinal problem).
Many different spinal problems (slipped disc, fractured spine, spinal infection, spinal tumour, ischaemic myelopathy) can cause similar signs. Ischaemic myelopathy is a disease that comes on very suddenly without warning and can be very frightening, however most affected dogs recover. If you suspect your dog might have a spinal problem (especially an acute one) you should make sure your vet checks them over as soon as possible.
Ischaemic myelopathy is a disease of the spinal cord (myelopathy) caused by a poor blood supply (ischaemia). Like any other part of the body, the spinal cord relies on a permanent blood supply to bring nutrients and remove waste products. Arteries supply defined segments of the cord on each side. If one of these arteries becomes blocked the blood supply to a particular area of the spinal cord is shut off and this causes damage to the nerves running there.
The most common cause of blockage is a fragment of the cushion (disc) between the bones in the back. This disc is made of a tough cartilage (fibrocartilage) and so the term fibrocartilagenous embolism (literally meaning fragment of fibrocartilage blocking an artery) is often used to describe the condition. There are many theories, but no-one really knows how or why this fragment of intervertebral disc suddenly gets into the spinal cord artery. There are many other more unusual causes of blockage (a fragment of tumour or fat).
Ischaemic myelopathy is a common cause of sudden paralysis in dogs, particularly large and giant breeds. This condition can cause paralysis of one back leg, both back legs, all four legs or only one side of the body (depending on which portion of spinal cord is affected). Typically, this paralysis comes on suddenly, is not painful and does not get worse with time (at least after the first 24 hours).
Other diseases that cause sudden paralysis and may be mistaken for ischaemic myelopathy include slipped disc (intervertebral disc herniation see specific fact sheet), spinal fracture or dislocation (broken neck or broken back), spinal cord bruising (spinal cord contusion) caused by a road traffic accident or a bad fall.
A diagnosis of ischaemic myelopathy is often made by ruling out other causes of acute paralysis (see above). For this purpose, diagnostic tests such as spinal X-rays, myelography and/or MRI scan are indicated. It is important to rule out other conditions causing pressure on the spinal cord (slipped discor spinal fracture/dislocation) where an operation might be needed.
In most animals with ischaemic myelopathy the results of these tests come back as normal. Since your vet is relying on absence of findings on X-ray or MRI scan to make a diagnosis it is essential that the correct portion of the spinal cord is checked. Occasionally, swelling of the spinal cord can be detected on X-rays or MRI scan.
A definite diagnosis of ischaemic myelopathy and identification of its exact cause can only be made by examining the spinal cord after death.
There is no specific treatment for ischaemic myelopathy but most dogs tend to recover within a few weeks provided they have retained the ability to feel pain in their feet. Good nursing care (physiotherapy, assisted walking, hydrotherapy, adequate bedding to prevent bed sores) is essential for the recovery of the animal. The recovery period may be long and require intensive nursing so can be quite expensive.
If your dog did not lose sensation in its feet then it will probably recover over a few weeks. Most dogs will make a full recovery after 8 to 12 weeks but some may keep some residual deficits. In animals where there was complete paralysis, improvement may not be seen for a number of weeks and some animals may never fully recover.