What is 'Wobbler'?
The term 'wobbler' originated from a spinal disease of horses that results in a lack of coordination when walking. 'Wobbler' in dogs describes lower cervical spinal cord (i.e. neck area) and nerve root compression in large breed dogs that occurs due to developmental malformations, instability or instability associated changes in the spinal cord. Affected dogs show a wobbly gait when walking or running as a result of pressure on the spinal cord in the lower part of the neck. Many of them stumble when walking, and often the rear legs are firstly affected.
Wobbler syndrome is common in Great Danes and Doberman Pinschers with males are affected more often than females. The condition can be first noticed any time between 7 weeks and 10 years old.
How Does Wobbler Occur?
The disease starts when there is instability between 2 or more vertebrae in the lower part of the neck. The body tries to correct this instability resulting in thickening of the ligaments that are within the vertebral joints. As the ligaments thicken they put pressure on the spinal cord.
The spinal cord is similar in structure to a telephone cable in the sense that it contains thousands of nerve fibres each carrying important messages (just like a telephone cable contains many wires carrying important messages). As the spinal cord is compressed by the thickened ligaments, nerve fibres are prevented from being able to carry messages from the brain to the nerves in legs. This in turn causes the dog to walk abnormally (often with a wobble).
What Signs do Affected Dogs Show?
Characteristically there is a slow progression of paralysis and an uncoordinated or wobbly gait, especially in the hind legs. A broad based stance is also often seen with the back legs. Sometimes milder signs are also seen in the front legs such as a stiff leg gait or scuffing of the front toe nails.
Slow progressive deterioration is common, but occasionally a traumatic epiosode causes an acute exacerbation of the signs. Resistance and pain upward extension of the neck are quite often seen.
The uncoordinated gait is due to pressure on the spinal cord from the thickened ligaments. The instability between the vertebrae puts further unnatural stress on the discs located between the unstable vertebrae. The discs may eventually rupture, producing great pressure on the overlying spinal cord which in turn leads to paralysis of either the front legs or all four legs.
How is Wobbler Confirmed?
The history of how the dog walks, clinical signs demonstrated and clinical findings on examination will give a suspicion of wobbler syndrome. The suspicion can be confirmed with radiographs which rule out other possible causes of abnormal gait including tumours, disc disease, infections and inflammatory spinal cord diseases.
Properly positioned X-rays under general anaesthesia will show poorly aligned cervical vertebrae with a tipping of part of the vertebrae into the spinal cord, bone reaction around the front of vertebrae, collapsed disc spaces and degeneration of the junction of the involved vertebrae. Myelography, which utilises injection of contrast material around the spinal cord, indicates the points of pressure at the spinal cord.
How can Wobbler be Treated?
Medical and surgical treatment may relieve the clinical signs. Exercise restriction together with cortisone administration will result in temporary improvement in nerve function, and sometimes long term management of dogs with mild signs of nerve dysfunction is satisfactory.
Although initial improvement is common after medical therapy, the underlying compression and instability persist and may progress without surgical intervention.
Surgery is recommended in mildly affected cases if the condition does not improve or continues to deteriorate despite medical treatment. Surgery is recommended in all severely affected cases. The aim of surgery is to remove pressure from the spinal cord. Several surgical procedures have been described with the most successful procedure being governed by the findings on the myelograms.
What are the Chances of a Successful Outcome?
Affected dogs show variable progress depending on the neurological signs present, progression of disease and specific spinal cord defects present. Dogs that are still able to walk and with a short history and only one spinal cord lesion may have 80% success rate after surgery. However, the outcome is poor if multiple spinal cord lesions are present, the signs have been present for a long time and the dog is unable to walk.