The spine is made up of approximately 31 vertebrae: 7 cervical (neck), 13 thoracic (chest), 7 lumbar (lower back), 3 fused sacral (pelvis) and a varying number of coccygeal (tail). The spinal cord is encased inside the vertebrae for protection. The spinal cord is basically an extension of our brain. Running from Cervical spinal anatomyhead to tail, the spinal cord carries messages from the brain to the rest of the body and back again. Lying between each vertebrae and below the spinal cord, are small cushions called intervertebral discs. These discs act as shock absorbers between each adjacent vertebrae, providing protection and spinal flexibility. Intervertebral discs are madeup of two regions: a gelatinous nucleus (nucleus pulposus) and a surrounding fibrous ring (annulus fibrosis). When the nucleus calcifies, losing its jelly-like consistency, it no longer cushions the vertebrae, predisposing the disc to bulging and rupture. The resulting pressure on the spinal cord leads to pain and even paralysis. Cervical disc disease is most commonly seen in chondrodystrophic breeds like: the Dachshund, Corgi, Lhasa Apso, ShihTzu, Beagle, Pekingese, Cocker Spaniel and Poodle.
In cervical spine lesions the majority of patients demonstrate neck pain as the first and most persistent clinical sign. The head and neck are held in a tense, guarded position. The patient does not want to elevate the head and neck. The guarding position results in muscle spasms, giving the neck a thickened appearance. Discs do not always rupture in the same way. When a disc ruptures on one side of the cord the result can be neurological deficits in only one front leg. However, if a disc ruptures in the center of the spinal canal, both front and rear legs can become affected. The speed at which a disc ruptures and compresses the spinal cord is just at important as how much compression there is on the cord. For example, some patients may experience more severe neurological deficits, despite minimal compression, when the disc ruptures rapidly placing sudden compression on the cord.
Cervical myelogramsDiagnosis of a ruptured disc is based on the history of symptoms and a neurological exam. Standard radiographs can show calcified discs and narrowed disc spaces but this alone does not confirm the location of cord compression. A myelogram (contrast dye study) or an MRI is necessary to pinpoint the location of the disc in question. Cervical discs, unlike discs in the thoracic and lumbar regions, generally rupture slowly. Larger vertebral canal spaces for the spinal cord to passthrough give the ruptured contents more room, resulting in less compression. Most patients experience waxing and waning periods of discomfort. Medical treatment is often the choice in early or mild cases. Corticosteroids and muscle relaxants are used to help relieve cord swelling, pain and subsequent muscle tension. However, as more disc material pushes on the spinal cord, medical therapy is not enough and surgical intervention becomes necessary.
Once the site of compression has been determined the surgeon removes all the ruptured disc material using a ventral slot decompression technique preformed through an incision under the neck. In addition to the ventral slot decompression, the surgeon will often fenestrate the discs on either side of the herniation. Fenestration means that a small window is created in the outer fibrous ring of the disc and the center contents are removed. This procedure hopefully prevents ruptured discs in the future.
Patients usually spend 2- 3 nights in the hospital and generally stay on corticosteroids and an analgesic (pain medication) for about a week. When a patient returns home we recommend restricted activity for at least 3 weeks. Restricted activity means no running, jumping, excessive stairs or rough play and outside on a leash for all bathroom breaks. In addition, we strongly recommend that all owners purchase a harness to use and not return to the use of a collar and leash combination.