The spine of the dog extends from the base of the skull and includes the neck, back, and the tail. The spine is made of many interlocking bones called vertebrae. A shock absorbing structure called the intervertebral disc is located between each vertebra, except for the first and second vertebrae located in the neck. The spinal cord runs through a large canal within the bones of the vertebrae. The spinal cord is similar to a telephone cable that has many wires, which transmits signals from the brain to control the internal organs and the muscles.
What is wobbler syndrome?
Wobbler syndrome, also called cervical spondolytic myelopathy, is a multifactorial disease that compresses the spinal cord in the neck. This results in damage and dysfunction of the spinal cord. Abnormalities of the spine that contribute to this condition include narrowing of the vertebral canal; protrusion of the intervertebral disk; thickening of the ligament located immediately beneath the spinal cord; partial dislocation of the neck bones; and thickening of the joints of the vertebrae. The compression of the spinal cord may be static, meaning that flexion, extension or traction of the neck does not change the amount of compression on the spinal cord. Other cases have a dynamic compression of the spinal cord, meaning that the amount of compression on the spinal cord changes with movement of the neck (flexion, extension and traction).
Signs and diagnosis
Adult great Danes and doberman pinschers are the most commonly affected breeds. Clinical signs of wobbler syndrome include neck pain and weakness of the limbs. The dog may appear to be wobbly or drunk when walking. The forelimbs may be more severely affected than the hind limbs. Intermittent knuckling of the paws is common as the disease progresses.
The diagnosis of wobbler syndrome is based on physical examination findings and diagnostic imaging tests. The neurologist will perform a myelogram, which involves injecting dye into the fluid column that surrounds the spinal cord. X-rays and a CT scan are used to reveal the region of compression on the spinal cord. A traction force is then applied to pull the neck bones slightly apart, and then X-rays or a CT scan is repeated to see if the compression on the spinal cord is alleviated. MRI is another diagnostic test that may used to diagnose the problem.
There are two types of surgery that are used for the wobbler patient. The type of surgery required is dependent on the results of imaging tests. If the compression of the spinal cord does not change with traction on the neck, then a dorsal laminectomy or a ventral slot surgery may be recommended. The dorsal laminectomy involves removal of the roof of the spinal canal (top of the vertebra) in the area of the spinal cord compression. The ventral slot involves removing some bone beneath the spinal cord along with scar tissue and protruding disc that may be compressing the spinal cord. If the patient has a dynamic compression of the spinal cord, the spine is distracted, a bone graft is placed within the affected disc space and the spine is stabilized with a locking plate or other surgical implants.
The recovery can be a lengthy process, often months. In addition, extended nursing care is required for many patients to bring them back to ambulatory function. One study of 104 cases of wobbler syndrome showed that 81% of those treated surgically had improved neurological function, 3% unchanged, and 16% worse than prior to surgery. Of those treated medically, 54% were improved, 27% were unchanged, and 19% had progressive worsening of their clinical condition. There was no difference in the survival times of either group (medical 46.5 months vs. surgical 48 months).
A new technique of fusion of the spine with bone graft and locking plate technology in 10 dogs resulted in an 80% successful outcome with no recurrence of clinical signs in 70% of the cases.
For more information on this subject, speak to the veterinarian who is treating your pet.