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Cervical disorders of large breed dogs (Proceedings)

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Nov 01, 2009

Disease processes of the cervical spinal cord and vertebral column and the pain and paresis produced by these disorders are a common cause of presentation to the veterinarian. Large breed dogs are not immune to cervical disorders and in some instances have conditions that are unique to their size. Other disorders affect both large and small breed dogs but the clinical course, treatment and prognosis may vary between dogs of different sizes. Fortunately, by recognizing the clinical signs of cervical disease and developing a list of differential diagnoses, a diagnostic and treatment plan can often be formed to help relieve a patient of pain and regain the ability to walk.

Clinical signs, neurologic examination and diagnostic procedures

The clinical approach to cervical pain in large breed dogs is similar to that in smaller breeds and is addressed in the section of these proceedings covering cervical pain in small breed dogs.

Differential diagnosis

     Intervertebral disc extrusion

One of the most common causes of cervical pain in veterinary patients is caused by extrusion of intervertebral disc material into the spinal canal. Chondroid degeneration of the intervertebral disc resulting in type I (acute) extrusion of the nucleus pulposus or a more chronic type II protrusion of the annulus fibrosus may both occur in large breed dogs. Type I disc extrusions occur more frequently than has been suggested in the past while type II disc protrusions remain a common component of caudal cervical spondylomyelopathy (Wobbler's syndrome). Large breeds with increased incidence of cervical intervertebral disc extrusion include the Doberman Pinscher, Rottweiler, Dalmatian, Weimaraner, German Shepherd and Labrador Retriever, although a disc extrusion may occur in any breed. Symptoms range from cervical pain to non-ambulatory tetraplegia, but paresis is not as common in cervical intervertebral disc disease compared to thoracolumbar disc extrusion. Despite this, a larger percentage of large breed dogs with cervical intervertebral disc extrusion/protrusion do have clinical paresis compared to smaller breeds. In the most severely affected patients cervical pain may be minimal or absent. Intervertebral disc extrusion/protrusion is a very unlikely differential diagnosis for patients less than two years of age.

Diagnosis of cervical disc extrusion may be obtained by survey radiographs if calcified disc material can be seen in the spinal canal but intervertebral disc calcification is not as prevalent in large breeds as in chondrodystophic and smaller breeds. In situ disc calcification does not equal intervertebral disc extrusion and calcification of a disc is not required before extrusion can occur. CT myelography or MRI is recommended to confirm the exact location of extruded disc material prior to surgical intervention. This is especially important in the cervical vertebral column since multiple surgical approaches are available in this area of the spine. In large breed dogs, disc extrusions are more common in the lower cervical vertebral column (C5-C6 and C6-C7).

Both conservative and surgical treatments are available for patients with cervical intervertebral disc extrusion. Conservative treatment, consisting of strict crate confinement and anti-inflammatory agents, may be attempted the first time a patient experiences mild to moderate pain. Corticosteroids generally provide better anti-inflammatory effects and analgesia than non-steroidal anti-inflammatory drugs (NSAIDs) for cervical disc extrusion, but NSAIDs may provide adequate analgesia in many patients with mild to moderate pain. Mixing corticosteroids and NSAIDs is contraindicated as the chance of gastrointestinal side effects is greatly increased without significantly changing the amount of analgesia provided. Use of analgesics and anti-inflammatory drugs without exercise restriction is also contraindicated and may result in significant worsening of clinical signs. For patients with severe cervical pain, any degree of paresis, or patients with repeat or chronic pain, decompressive surgery is usually necessary to provide long term pain relief. When the disc extrusion is centrally located within the spinal canal, decompression can usually be obtained with a ventral slot decompression. When disc material is located lateral to the spinal cord or within the intervertebral foramen, a dorsal laminectomy or hemilaminectomy is necessary to decompress the spinal cord. The prognosis for recovery is often very good but larger dogs may require longer to recover than patients of smaller breeds. The prognosis for recovery is better for patients with acute type I extrusions than for patients with type II protrusions associated with caudal cervical spondylomyelopathy.