Back problems in dogs are not uncommon. Many breeds are affected by disk disease but diseases of the spinal cord itself are also a problem. These diseases are painful and affect a dogs mobility. Medical management may help some dogs, but in severe cases surgery may be needed.
What is the cauda equina?
The cauda equina is part of the spinal cord. It is so-called because the collection of nine nerves which make it up somewhat resemble a horses tail in appearance (cauda = tail; equina = horse). The cauda equina is found towards the end of the spinal cord (the base of the spine). It produces the nerves that control some movements of the back legs, the tail and help to maintain urinary and faecal continence. The spinal cord itself runs through a bony tunnel or channel within the bones of the back (vertebrae). The bones surround and protect the delicate nervous tissue. All the individual vertebral bones connect with each other and allow great flexibility within the different areas of spine, e.g. neck, lower back. Normal function depends on a healthy spinal cord and a mobile and flexible spine.
What is cauda equina syndrome?
Cauda equina syndrome describes a collection of diseases that arise when the nerves of the cauda equina become compressed or trapped. Pressure on nerve fibres causes signs such as pain and paralysis, faecal and/or urinary incontinence, or pelvic limb lameness (similar to sciatica in humans). The most common disease causing problems is lumbo-sacral stenosis. In this disease the space that runs through the bones of the spine (vertebrae) is narrow, resulting in pressure on the delicate nerves contained within. Lumbo-sacral stenosis is seen most often in large breed dogs, such as German Shepherds. Other diseases can also cause pressure on the cauda equina nerves, e.g. tumours or inflammation, however these are not as common as lumbo-sacral stenosis.
Why does it develop?
Narrowing of the spinal canal and the resulting pressure on nerves is often caused by disc disease. Intervertebral discs act like cushions between adjacent vertebrae, but as in humans (e.g. people suffering from slipped disc) they can become diseased. In dogs with lumbo-sacral stenosis, a part of the spinal disc may bulge into the space where the nerves are located, compressing them. Other structures in the area may also become thickened, worsening the compression on the nerves. Several other conditions can lead to similar signs in dogs:
Discopondylitis is infection of the spinal discs and nearby bone. Affected dogs show lameness, pain and fever. Treatment is with antibiotics and sometimes surgery.
Trauma such as a fall or road accident may damage the back. Treatment may be strict rest and/or surgery.
Tumours can cause compression of the cauda equine. Treatment may be possible depending on the type of tumour and location.
Congenital problems are an occasional cause of similar signs.
Fibro-cartilaginous embolism may occur when a small portion of damaged disc detaches and interferes with the blood supply to the cauda equina nerves. Most dogs recover from this providing the embolism has not caused permanent damage to the spinal cord.
How do I know if my dog has cauda equina syndrome?
Signs are most common in large dogs of middle to older age, but often also seen in young adult working-type dogs. Often, affected animals will yelp loudly when jumping into a car or negotiating steps. They may show pain around the lower back area (above the head of the tail), and can also appear weak on the hind legs. The nails of the hindfeet may be scuffed and worn down abnormally. In severe cases there may be urinary and faecal incontinence and lameness in one of the back legs. Note that other common diseases such as hip dysplasia and arthritis can also result in some of these signs, so accurate diagnosis is important.
How will my vet know what is wrong with my dog?
A single X-ray is unlikely to lead to a confirmed diagnosis. Additional techniques such as a myelogram or discography are usually needed. These techniques use special dyes which are injected into the area to help highlight the source of the problem to find out where the compression is taking place. Your vet may suggest a CT or MRI scan, as used in humans. More and more animals are benefiting from these advanced techniques of looking inside the body. Your vet may want to send your dog to see a specialist for these investigations.
Is there any treatment for the condition?
Treatment and outcome depend on the cause of the condition in individual cases. Affected dogs are helped by rest, painkillers and avoidance of circumstances which cause pain. Try to arrange the environment where your dog is kept so that steps and any jumping activities are removed or avoided. Use of a blanket sling is helpful if pain is severe at times place a thick blanket under the dogs abdomen just in front of the hind legs and use this to help support weight. Ensure there is a plentiful supply of thick bedding where your dog lies. Exercise should be moderate but regular. Acupuncture has been reported to have some beneficial effects and your vet may be able to arrange a referral. Weight loss may improve signs in overweight dogs. This treatment is appropriate in all dogs where signs are not to severe, and in very old patients where surgery is thought undesirable. In more severe cases, especially if they do not respond well to other measures, surgery offers the best chance of success. Back surgery can permanently relieve the compression on the nerves. The outlook is usually good after successful surgery. Your dog should be referred to a specialist surgeon for this operation.